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comp.sys.hp48 FAQ : 3 of 4 - Appendices

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Archive-name: hp/hp48-faq/part3
Last-modified: 5/16/1999
Version: 4.59
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post72
  9.1.  ASC Functions

  Note: Although this document mentions SX only, ASC\-> and \->ASC work
  on both the SX and GX.

  From: Bill Wickes

  ASCII Encoding HP48 SX Objects

  Sending an HP48 SX object via electronic mail can be difficult if the
  object does not have an ASCII form, such as is the case for library
  objects.  There are various encoding schemes available on different
  computer systems, but these require that the sender and receiver have
  similar computers, or at least compatible encode/decode schemes.  The
  programs listed below perform the encoding and decoding on the HP48 SX
  itself, which has the advantage of being completely independent of any
  computer.

  The programs are nominally called \->ASC and ASC\->.  The former takes
  an object from the stack and converts it to a string, in which each
  nibble of the object and its checksum is converted to a character 0-9
  or A-F.  (The object must be in RAM, otherwise a "ROM Object" error is
  returned.)  For sake of easy inclusion in e-mail letters, the string
  is broken up by linefeed characters after every 64 characters.

  ASC\-> is the inverse of \->ASC: it takes a string created by \->ASC
  and converts it back into an object.  When you transmit the encoded
  strings, be sure not to change the string; ASC\-> uses the checksum
  encoded in the string to verify that the decoding is correct.  An
  "Invalid String" error is returned if the result object does not match
  the original object encoded by \->ASC.  When you upload a string to
  your computer, use HP48 translate mode 3 so that the HP48 will convert
  any CR/LF's back to LF's when the string is later downloaded.

  Two versions of ASC\-> are included here.  The first (P1) is in HP48
  user language, using SYSEVALs to execute system objects.  P2 is a
  string that the setup program uses P1 to decode into an executable
  ASC\-> - then P1 is discarded.  The second version is more compact
  than the first, and also uneditable and therefore safer (but it can't
  be transmitted in ASCII form, which helps to make the point of this
  exercise).

  Here are the programs, contained in a directory (if you have problems
  with this and you are using the HTML version of the FAQ, you may wish
  to try the plain text version or download a binary copy of the
  program):


  %%HP: T(3)A(D)F(.);
  DIR
  P1              @ ASC\-> Version 1.
  \<<
    IF DUP TYPE 2 \=/
    THEN "Not A String" DOERR
    END RCWS \-> ws
    \<< 16 STWS
      #0 NEWOB SWAP DUP SIZE
      IF DUP 4 <
      THEN DROP SWAP DROP "Invalid String" DOERR
      END
      DUP 65 / IP - 4 - # 18CEAh SYSEVAL
      "" OVER # 61C1Ch SYSEVAL
      SWAP # 6641F8000AF02DCCh
      # 130480679BF8CC0h # 518Ah SYSEVAL
      # 19610313418D7EA4h # 518Ah SYSEVAL
      # 7134147114103123h # 518Ah SYSEVAL
      # 5F6A971131607414h # 518Ah SYSEVAL
      # 12EA1717EA3F130Ch # 518Ah SYSEVAL
      # 280826B3012808F4h # 518Ah SYSEVAL
      # 6B7028080BEE9091h # 518Ah SYSEVAL
      # BE5DC1710610C512h # 518Ah SYSEVAL
      # 705D00003431A078h # 518Ah SYSEVAL
      # 3D8FA26058961431h # 518Ah SYSEVAL
      # 312B0514h # 518Ah SYSEVAL
      # 18F23h SYSEVAL
      DUP BYTES DROP 4 ROLL
      IF ==
      THEN SWAP DROP
      ELSE DROP "Invalid String" DOERR
      END ws STWS
    \>>
  \>>

  P2      @ ASC\->  Version 2.  To be converted by ASC\-> version 1.

  "D9D20D29512BF81D0040D9D20E4A209000000007566074726636508813011920
  140007FE30B9F060ED3071040CA1304EC3039916D9D2085230B9F06C2A201200
  094E66716C696460235472796E676933A1B21300ED30FD5502C230C1C1632230
  CCD20FA0008F14660CC8FB97608403104AE7D814313016913213014117414317
  414706131179A6F5C031F3AE7171AE214F8082103B6280821909EEB0808207B6
  215C0160171CD5EB870A13430000D50713416985062AF8D341508813044950B9
  F06BBF06EFC36B9F0644230C2A201200094E66716C696460235472796E676933
  A1B2130B21300373"

  P3      @\->ASC.     To be converted by ASC\->.
  "D9D20D2951881304495032230FD5502C230A752688130ADB467FE30322306AC3
  0CB916E0E30CBD30F6E30C1C1632230CCD20DC0008F14660CC8FB97608403104
  AE7D8143130169174147061741431311534AC6B4415141534946908D9B026155
  4A6F53131F3AE731A014C161AE215F08082103A6280821939EEC08082170A621
  4C161170CD56B870A18503430000D5071351796A9F8D2D02639916D9D2085230
  C2A209100025F4D402F426A6563647933A1B2130A2116B213033C0"

  SETUP   @Automatic setup program
  \<< P2 P1 'ASC\->' STO
      P3 ASC\-> '\->ASC' STO
      { P1 P2 P3 SETUP } PURGE
  \>>

  END


  Installation instructions:

  1. Save the above text into a text file named CONV (for example).  Be
     sure that you leave the strings exactly as entered above, with no
     extra spaces or other invisible characters at the beginnings or
     ends of the lines.

  2. Set the HP48 SX into ASCII transfer mode.

  3. Using Kermit, download CONV text file to the 48, verify its
     checksum (6C8Ah).

  4. Execute CONV to make it the current directory.

  5. Execute SETUP.

  6. The directory CONV now contains ASC\-> and \->ASC, ready to use.

  To archive the decoded versions of ASC\-> and \->ASC back on your
  computer, be sure to set the HP48 SX in binary transfer mode before
  uploading.

  Disclaimers:

  o  Use the programs at your own risk.  Any time you delve into the
     SYSEVAL world, there are increased dangers.  Archive your 48 memory
     before experimenting with these programs!  Also, verify the
     checksums of objects defined above to make sure they have been
     downloaded correctly, before executing ASC\->.

  o  I will not answer questions about how the programs work.  This is
     not because of any great secrecy, but rather because it's hard to
     give any answer that doesn't lead to more questions, and more, and
     more...

  o  48 hackers are welcome to mine any nuggets they can from the
     programs, and from the fact that \->ASC is a convenient way to
     decompile an object.


  9.2.  OBJFIX

  When a binary object received by Kermit on the HP-48 is left as a
  string beginning with HPHP48, OBJFIX will extract the HP-48 object if
  the only problem is that extra bytes got appended to the end.

  OBJFIX takes a variable name in stack level 1 and modifies the
  contents of the variable if no other problems are detected.

  Note: This is like FIXIT by Horn and Heiskanen on Goodies Disk 8, but
  this one is by HP and so I suppose it's more reliable.  Although it
  fails the test cases included with FIXIT, that may be because they
  were artificially contrived cases.  Try both on real-world downloads
  that need fixing.  Which do you like better?

  OBJFIX.ASC


       %%HP: T(3)A(D)F(.);
       "D9D202BA81D9F81B2040D9D20F2A26DA91629C8145126489162C23072C80CCD2
       0BD0008FB9760147108134164142C2818F24D534501008B2F41643150D73B840
       58405438314A161966D2BF6BF6A6F5BE16314213114334CF8208A6F58F235A04
       55136D7D4EA494D231A1CA101110131CA130DBE284F8FC0760D41198F29960D4
       130142119EA1408F5E0108D341503223072D70B2130B21301460"


  9.3.  FIXIT

  From: Joe Horn and Mika Heiskanen


     PURPOSE:
        Converts a badly uploaded string into the original object.

     THEORY:
        A lot of folks upload HP48 objects poorly, such that when you
        download them, you just get strings full of garbage that look
        something like this:


          "HPHP48-E#c&r$a%p@!*!..."     [looks familiar, eh?]


     That's because they uploaded it using XMODEM, or managed to screw
     it up some other way.  The following FIXIT program takes such a
     string and extracts the actual HP48 object that they originally
     intended to upload (if at all possible).

     Such object extraction can be done by hand, but it's too dangerous.
     FIXIT minimizes the danger of Memory Clear.  It checks whether the
     extracted object is a valid one, and if not, drops it from the
     stack before the HP48 attempts to display it.  All of the many bad
     downloads I've archived over the years are fixed by FIXIT, whereas
     about half of them cause a Memory Clear when extracted manually.
     No guarantees, however.  Use at your own risk.

     The actual extraction is done by a "Code object" written by Mika
     Heiskanen.  The User RPL "shell" around this code object is what
     minimizes the danger of Memory Clear; it was written by Joe Horn.

     INSTRUCTIONS:
        BACKUP YOUR MEMORY, just in case the string contains a logic
        bomb.

        Place the bad download on the stack (see "HPHP48-...") and run
        FIXIT.

        Possible results:

     o  No error: the object was extracted successfully and is on level
        1.

     o  "Bad Argument Type" error: you didn't have a string on level 1.

     o  "Bad Argument Value" error: the string wasn't of the proper
        form; it must be an "HPHP48-..." downloaded string.

     o  "Invalid Definition" error: the object was mangled in
        transmission so badly that its end was lost; the object cannot
        be extracted.

     o  "Undefined Result" error: there is no HP48 object in the string.

     o  "Recover Memory? YES/NO": the string contained a bomb, and FIXIT
        detonated it.  Press YES to sift through the shrapnel and rubble
        in a feeble attempt to resurrect the dead.  Press NO to bury
        them.

     EXAMPLES:
        To do the following examples, download the FIXIT directory to
        your HP48 and get into it.

     o  Press HI.  See "HPHP48-E...", a badly uploaded download.  Before
        pressing FIXIT to fix it, try doing what we all used to do:
        press EDIT to see if we can recognize anything (usually a futile
        attempt).  We see:

        "HPHP48-E...  << Melancholy Baby >>"

        But looks can be deceiving; press ON to exit the editor, and
        then press FIXIT to extract the intended upload:

        << Happy Camper >>

     o  Press WTAV; see another garbage download.  But EDIT refuses; the
        string contains null characters.  Press FIXIT; see successfully
        extracted directory.

     o  Press BAD1.  Notice that it looks exactly like WTAV.  (Press
        WTAV, compare, then DROP).  But its ending is all messed up;
        manually extracting WTAV from BAD1 can cause Memory Clear.
        Press FIXIT and see "Error: Invalid Definition" indicating that
        the object inside BAD1 is so mangled that its end cannot be
        located.

     o  Press BAD2.  Looks like WTAV again.  But its body is messed up;
        manually extracting it would create an External object that
        could cause Memory Clear if evaluated.  Press FIXIT and see
        "Error: Undefined Result" indicating that there is nothing
        recognizable inside BAD2.

  FIXIT.ASC


       %%HP: T(3)A(D)F(.);
       "69A20FF7CE20000000402414442340C2A203B000840584054383D25403A20FF7
       2500000000403535947440D9D20E16329C2A2DBBF13013216DF1406A1C42328D
       BF193632B213034000407545146540D9D20E163292CF1EFFB1DBBF1EBFB150FA
       193632B2130003030303034C000402414441340C2A203B000840584054383D25
       469A20FF72500000000403535947440D9D20E16329C2A2DBBF13013216DF1406
       A1C42328DBF193632B213034000407545146540D9D20E163292CF1EFFB1DBBF1
       EBFB150FA193632B2131313131313134C000407545146540C2A203B000840584
       054383D25469A20FF72500000000403535947440D9D20E16329C2A2DBBF13013
       216DF1406A1C42328DBF193632B213034000407545146540D9D20E163292CF1E
       FFB1DBBF1EBFB150FA193632B2130003030303034C00020849420C2A20570008
       40584054383D254D9D20E163284E2050841607079784E20603416D6075627936
       32B2130A0BA02D456C616E63686F6C697022416269702BB28000506494859445
       50D9D20E16323CE2278BF168BC1ED2A2167E1AFE22D9D203CE2278BF19C2A274
       3A2C58C1C2A2031000840584054383D2167E1AFE22D9D2078BF18B9C1DBBF1AA
       F028DBF1CCD201200014713717917F137145142164808C5BF22D9D2033920200
       0000000005150933A1B21305DF22B21305BF22D9D20339202000000000004150
       933A1B21305DF223CE2278BF168BC1D8DC1167E1AFE22D9D203FBF1339202000
       000000002770933A1B21305DF223CE2278BF19D1A1DBBF18DBF1E0CF1D5CE1AF
       E22D9D208DBF1339202000000000000030933A1B21305DF22CB2A193632B2130
       B21303D4F"


  9.4.  LASTX

  The LASTX function is useful in calculations where a number occurs
  more than once.  By recovering a number using LASTX, you do not have
  to key that number into the calculator again.  Note however that LASTX
  uses the built in last argument feature, so if you use LASTX you will
  lose the contents of your LASTARG.

  For example, calculate:


        96.704 + 52.394706
       --------------------
             52.394706

       Keystrokes:                     Stack:
       -----------------              --------------------
       96.704 ENTER                    96.704

       52.304706 +                     149.098706

       LASTX                           149.098706
                                       52.304706

       /                               2.84568265351

       @ This is a version of LASTX for the HP48
       @
       %%HP: T(3)A(D)F(.);
       \<< DEPTH \-> n
         \<< LASTARG DEPTH n
       - DUP \-> s
           \<< ROLLD s 1 -
       DROPN
           \>>
         \>>
       \>>


  9.5.  Compact Data Storage

  From: Jim Donnelly

  A simple length-encoding technique can be put to use for a free-
  format, very compact multi-field data storage system.  Two tiny
  programs, SUBNUM and STRCON are here to help the process, and are
  listed near the end of this note.  At the end of the note is a
  directory that may be downloaded into the HP48 that contains the
  examples.

  The principle is to store starting indices in the beginning of a
  string that point to fields stored subsequently in the string.  The
  indices are stored in field order, with an additional index at the end
  to accommodate the last field.  There are several small points worth
  mentioning:


  o  Fields may be 0-length using this technique.

  o  The execution time is uniform across all fields.

  o  This technique saves about 4 bytes per field after the first field,
     because the string prologue and length are omitted for fields 2 ->
     n.


     EXAMPLE:


                    Indices  |          Fields
     Character               |     1 11111111 12222222222
     Position :   1  2  3  4 |567890 12345678 90123456789
                 +--+--+--+--+------+--------+-----------+
     String :    | 5|11|19|30|Field1| Field2 |  Field 3  |
                 +--+--+--+--+------+--------+-----------+


     This is a string that contains 3 fields, and therefore 4 index
     entries.  The first field begins at character 5, the second field
     begins at character 11, and the third field begins at character 19.
     To keep the pattern consistent, notice that the index for field 4
     is 30, which is one more than the length of the 29 character data
     string.

     To extract the second field, place the string on the stack, use
     SUBNUM on character 2 to extract the starting position, use SUBNUM
     on character 3 to extract the (ending position +1), subtract 1 from
     the (ending position+1), then do a SUB to get the field data.
     NOTE: The index for field 1 is stored as char. data 5, NOT the
     string "5"!  To place the field index for field 1 in the string,
     you would execute "data" 1 5 CHR REPL.

     PROGRAM:
        The following program accepts an encoded data string in level 2
        and a field number in level 1:


          DECODE   "data"  field#  -->  "field"

          <<  --> f
            <<
              DUP f SUBNUM                ; "data" start -->
              OVER f 1 + SUBNUM           ; "data" start end+1 -->
              1 -                         ; "data" start end -->
              SUB                         ; "field" -->
            >>
          >>


     DATA ENCODING:
        The following program expects a series of 'n' strings on the
        stack and encodes them into a data string suitable for reading
        by the first example above.

        The programs SUBNUM and STRCON are used to assemble the indices.


     ENCODE      field n  ...  field 1   n   -->  "data"

     << DUP 2 + DUP 1 - STRCON --> n  data
       <<
         1 n
         FOR i
           data i SUBNUM OVER SIZE   ; ... field index fieldsize
           + data SWAP               ; ... field "data" index'
           i 1 + SWAP CHR REPL       ; ... field "data"'
           SWAP + 'data' STO         ; ...
         NEXT
         data                        ; "data"
       >>
     >>


     In this example, four strings are encoded:


          Input:  5: "String"
                  4: "Str"
                  3: "STR"
                  2: "STRING"
                  1:         4


     Output: "xxxxxSTRINGSTRStrString"      (23 character string) (The
     first five characters have codes 6, 12, 15, 18, and 24)

     VARIATION:
        The technique above has a practical limit of storing up to 254
        characters of data in a string.  To overcome this, just allocate
        two bytes for each field position.  The code to extract the
        starting index for becomes a little more busy.  In this case,
        the index is stored as two characters in hex.


                         Indices  |          Fields
          Character               | 11111 11111222 22222223333
          Position :   12 34 56 78|901234 56789012 34567890123
                      +--+--+--+--+------+--------+-----------+
          String :    |09|0F|17|21|Field1| Field2 |  Field 3  |
                      +--+--+--+--+------+--------+-----------+


          <<  --> f
            <<
               DUP f 2 * 1 -           ; "data" "data" indx1 -->
               SUBNUM 16 *             ; "data" 16*start_left_byte  -->
               OVER f 2 * SUBNUM +     ; "data" start
               OVER f 2 * 1 + SUBNUM   ; "data" start end_left_byte -->
               16 * 3PICK f 1 + 2 *
               SUBNUM + 1 -            ; "data" start end -->
               SUB                     ; "field"  -->
            >>
          >>


     TWO VERY TINY HELPFUL PROGRAMS:


          SUBNUM          "string"  position  -->  code

          << DUP SUB NUM >>


          STRCON          code  count  -->  "repeated string"

          << -->  code count
            << "" code CHR 'code' STO
               1 count START code + NEXT
            >>
          >>


     Alternative Solution to the Problem:
        From: Matjaz Vencelj <vencelj@fmf.uni-lj.si>

        Jim allocates two bytes for each index entry (to handle longer
        strings), but on the other side obviously only uses values
        00...FF for index dublets, which just doesn't make sense.  He's
        at a 16*16 = 255 chars limit again!

        I have put together a working set of commands which support up
        to 65K strings, using two-byte indexing.

        The encoder (Encode) is User-RPL program which calls the binary
        N2C which converts the level 1 real into a 2 character string:


          @*** Encode ***
          %%HP: T(3)A(R)F(.);
          \<<
            IF DUP TYPE 0 = THEN 514 DOERR END
            \-> N
              \<<
              N 1 + 2 * #18CEAh SYSEVAL #45676h SYSEVAL
              1 N FOR I I 2 * 1 - OVER SIZE 1 + N2C REPL SWAP + NEXT
              N 2 * 1 + OVER SIZE 1 + N2C REPL
              \>>
          \>>


          @*** N2C, cksum=#8919h ***
          %%HP: T(3)A(R)F(.);
          "D9D202BA812BF819FF30D9D20AEC8111920001007FE3057A50C57463223057A5
          0EE250B2130B21307206"


     ASCII download them with translate code 3, then call program
     'Encode' with data strings in levels 2..n+1 and a real n in level 1
     indicating the number of strings.

     The string decoder (Decode), which is usually speed-critical, is
     the following \->ASC encoded binary:


          @*** Decode, cksum=#38E1h ***
          %%HP: T(3)A(R)F(.);
          "D9D20D8A81D9F811192013000D9D20AEC8113D26CA130F6E30CA130E0E305080
          311920001002CE30CAF0650803CBD30CAF06FED30F6E30CA130E0E3050803119
          20001002CE30CAF0650803CBD30E0E3033750B2130B21309534"


     It takes a `database' string on level 2 and a real (record
     position) on level 1, then comes back with the appropriate
     substring (record).


  9.6.  HP82240B Printer Codes

  From: Jarno Peschier


     Size of physical row
        One printed row is either 24 normal characters, 12 expanded
        characters or 168 pixels wide.  This means that one normal
        character has a width of 7 pixels. Any printed data "falling off
        the row" will be truncated and ignored by the printer.


     Reset


          ESC 255d


     This resets the printer to the following state: Roman8 character
     set (watch out: the power-up character set is ECMA94), both
     expanded and underline printing off, buffer cleared.


     Self test


          ESC 254d


     This causes the printer to print a selftest pattern.  This mainly
     consists of a printout of the Roman8 character set.


     Expanded printing


          ESC 253d


     This turns expanded printing on.  This means that from this code on
     all characters that are printed will be printed at twice the normal
     character width because each column of pixels is printed twice.
     Has no effect if expanded printing is already on.


          ESC 252d


     This turns expanded printing off.  This means that from this code
     on all characters that are printed at normal character width again.
     Has no effect if expanded printing is already off.


     Underlined printing


          ESC 251d


     This turns underlined printing on.  This means that from this code
     on all characters that are printed will be underlined because the
     bottom-most pixel in each columns of pixels is now always on. Has
     no effect if underlined printing is already on.


          ESC 250d


     This turns underlined printing off.  This means that from this code
     on all characters that are printed will not be underlined anymore.
     The bottom-most pixel in each columns of pixels is printed as it is
     defined for the printed character.  Has no effect if underlined
     printing is already off.


     Character sets


          ESC 249d


     This switches the printer to use the ECMA94 character set.  This
     set is 100% identical to the character set used in HP48 calcula-
     tors.  This is the power up default of the printer.  Has no effect
     if ECMA94 is the current character set already.


          ESC 248d


     This switches the printer to use the Roman8 character set.  This
     set is different than the character set used in HP48 calculators in
     the 128 last characters.  As far as I know this set is used by
     older printers like the HP82240A and by HP28 calculators (hence the
     need for the OLDPRT command in HP48 calculators if you are printing
     to a HP82240A).  This character set is turned on if you reset the
     printer with the reset code.  Has no effect if Roman8 is the cur-
     rent character set already.


     Graphics


          ESC n data (with n between 1 and 247)


     This causes the printer to print graphics specified by the speci-
     fied data (one byte per pixel column).  The value n specifies the
     number of bytes of data that follow the printer code that will be
     interpreted as graphics data.  Any data after pixel column 168 will
     be truncated and ignored.


  10.  Appendix B: GX Specific Information

  10.1.  What's new in the HP48 G/GX?

  From: Joe Horn


     AUTOMATIC LIST PROCESSING
        Almost all commands that did not accept list(s) as their
        arguments can do so now.  Here are just a few examples:


          { 1 2 3 } SF sets flags 1, 2, and 3
          { 1 2 3 } SQ  -->  { 1 4 9 }
          { 2 4 } 10 /  -->  { .2 .4 }
          10 { 2 4 } /  -->  { 5 2.5 }
          { 10 12 } { 2 4 } /  -->  { 5 3 }
          { .1 .2 .5 } ->Q  -->  { '1/10' '1/5' '1/2' }
          { freq freq ...} { dur dur ... } BEEP can play a song with no
            audible hiccup between tones.


     Since + has always been used to concatenate lists, a new ADD func-
     tion exists to add the elements of two lists, like this:


          { 1 2 3 } { 4 5 6 } ADD returns { 5 7 9 }, whereas
          { 1 2 3 } { 4 5 6 }  +  returns { 1 2 3 4 5 6 } as it did
            before.


     The only commands which do not have automatic list processing are:

     o  those which never get a Bad Argument Type error (like DUP),

     o  meta-object commands (like ROLL),

     o  program branch structures (like FOR), and

     o  commands that specifically work on lists (like GET).

        Sometimes the results are non-obvious, for example:


          5  { A B C }  STO           -->  A=5, B=5, C=5
          { 5 6 7 }  'A'  STO         -->  A={ 5 6 7 }  (same as on SX)
          { 5 6 7 }  { A B C }  STO   -->  A=5, B=6, C=7


     List processing is only recursive for ->Q and ->Qpi.

     PORTS AND MEMORY
        The HP48 G, like the 48 S, only has 32K RAM.  The GX, unlike the
        SX, has 128K RAM built-in.  Card slot 1 can contain another 128K
        (maximum), but card slot 2 can contain up to 4 megabytes of RAM.

        Only port 1 can be merged in the GX.  Card slot 2, which is
        intended for large-capacity RAM cards, is permanently "free",
        and is automatically divided up into 128K "ports", each of which
        becomes Port 2, Port 3, Port 4, etc.  Up to 4 Megabytes can be
        plugged into slot 2, which would then become Port 2 through Port
        33. (Although the FREE and MERGE commands were kept for HP48 SX
        compatibility, GX users will prefer the new FREE1 and MERGE1
        commands).  Therefore the maximum amount of merged main memory
        is 256K (unlike the SX which allowed up to 288K) after MERGE1;
        the maximum amount of fully online free independent memory is
        4224K after FREE1.

     LOCAL VARIABLES
        Variable names prefixed with a <- (backarrow character) are
        compiled as local (temporary) variable name objects even if
        they're not explicitly after FOR or ->.  This allows programs to
        share values through local variables, which is much faster than
        sharing values through global variables, and they get purged
        automatically.

     SPEED
        CPU clock speed is double the S/SX's, but throughput is
        estimated to be only 40% faster, primarily due to the fact that
        all RAM & ROM is now bankswitched (on the S/SX only a 32K
        portion of the ROM required bank switching), and it still has
        the same 4-bit bus bottleneck.

     IMPROVED COMMANDS:

     o  AXES can now also specify the spacing of the tick marks.

     o  DEPND can now also specify the initial values and tolerance for
        the new DIFFEQ plot type.

     o  REPL and SUB now work on arrays.

     HP SOLVE EQUATION LIBRARY CARD COMMANDS:

     o  AMORT, amortization calculations

     o  CONLIB, starts Constants Library catalog

     o  CONST, returns value of a named CONLIB constant

     o  DARCY, calculates Darcy friction factor


     o  EQNLIB, starts Equation Library catalog

     o  F0lambda, calculates black-body power fraction

     o  FANNING, calculates Fanning friction factor

     o  LIBEVAL is a generalized form of the EQ card's ELSYSEVAL; it
        executes any XLIB by its library number

     o  MCALC, marks an MSOLVR variable as "not user-defined"

     o  MINEHUNT, starts the "Minehunt" video game

     o  MINIT, initializes Mpar from 'EQ' for MSOLVR

     o  MITM, customizes title & menu of MSOLVR's screen

     o  MROOT, solve for variable(s) in MSOLVR

     o  MSOLVR, shows Multiple Equation Solver menu

     o  MUSER, marks an MSOLVR variable as "user-defined"

     o  SIDENS, density of silicon as function of temperature

     o  SOLVEQN, starts solver for specified EqLib equation(s)

     o  TDELTA, subtracts temperatures like "-" ought to but doesn't

     o  TINC, adds temperatures like "+" ought to but doesn't

     o  TVM, shows the financial calculator (Time Value of Money) menu

     o  TVMBEG, sets payments-at-beginning-of-periods mode

     o  TVMEND, sets payments-at-end-of-periods mode

     o  TVMROOT, solves for a TVM variable

     o  ZFACTOR, calculates gas compressibility factor Z

        Note: The EQ Card's Periodic Table and Tetris game are not in
        the HP48 G/GX, but the EQ Card can be used in the GX if those
        applications are needed. Tetris was not included because no
        agreement on royalty was reached.  The Periodic Table is
        available separately as freeware on HPCVBBS.

     NEW ARRAY COMMANDS:

     o  COL+, inserts a column vector into a matrix or a number into a
        vector (like INSCOL/PUTCOL in Donnelly's Tool Library)

     o  COL-, deletes a column from a matrix or number from a vector
        (identical to DELCOL in Donnelly's Tool Library)

     o  COL->, combines multiple column vectors into a matrix

     o  ->COL, breaks a matrix into multiple column vectors (like
        repeated GETCOL in Donnelly's Tool Library)

     o  COND, column norm condition number of a square matrix

     o  CSWP, swaps two columns in a matrix (like EXCOL in Donnelly's
        Tool Library)


     o  ->DIAG, returns vector of major diagonal elements of a matrix

     o  DIAG->, creates matrix with specified diagonal elements

     o  EGV, eigenvalues and right eigenvectors of a square matrix

     o  EGVL, eigenvalues of a square matrix

     o  FFT, discrete Fourier transform

     o  IFFT, inverse discrete Fourier transform

     o  LQ, returns the LQ factorization of a matrix

     o  LSQ, minimum norm least-squares solution to an ill-determined
        system of linear equations

     o  LU, returns the Crout LU decomposition of a square matrix

     o  PCOEF, returns polynomial with given roots (inverse of PROOT)

     o  PEVAL, evaluates polynomial at x

     o  PROOT, finds all roots of polynomial (inverse of PCOEF)

     o  QR, returns QR factorization of a matrix

     o  RANK, rank of a rectangular matrix (uses flag -54)

     o  RANM, creates matrix with random elements

     o  RCI, multiplies elements in one row of a matrix by a scalar

     o  RCIJ, does RCI then adds the result to a row

     o  ROW+, inserts a row vector into a matrix or a number into a
        vector (like INSROW/PUTROW in Donnelly's Tool Library)

     o  ROW-, deletes a row from a matrix or number from a vector
        (identical to DELROW in Donnelly's Tool Library)

     o  ROW->, combines multiple row vectors into a matrix

     o  ->ROW, breaks a matrix into multiple row vectors (like repeated
        GETROW in Donnelly's Tool Library)

     o  RSWP, swaps two rows in a matrix (identical to EXROW in
        Donnelly's Tool Library)

     o  SCHUR, computes the Schur decomposition of a square matrix

     o  SNRM, spectral norm of an array

     o  SRAD, spectral radius of a square matrix

     o  SVD, singular value decomposition of a matrix

     o  SVL, computes the singular values of a matrix

     o  TRACE, sum of diagonal elements of a square matrix

     GRAPHICS and PLOTTING COMMANDS:

     o  ANIMATE, displays grobs on the stack sequentially.  You can use
        the defaults, or specify your own delay between frames (can be
        very fast), the number of times to repeat the sequence, and even
        the pixel coordinates.  It's just like a ROLL REPL loop...
        except very fast.  Note: Charlie Patton converted 17 seconds of
        the Apollo moon-walk video into HP48 GROBs and ran them with
        ANIMATE, and it looked very good!

     o  ATICK, specifies tick spacing on plot axes

     o  EYEPT, specifies the eye-point coordinates in a perspective plot

     o  GRIDMAP, selects the new "gridmap" plot type

     o  PARSURFACE, selects the new "parametric surface" plot type

     o  PCONTOUR, selects the new "pcontour" plot type

     o  PICTURE, same as GRAPH command

     o  SLOPEFIELD, selects the new "slopefield" plot type

     o  WIREFRAME, selects the new "wireframe" plot type

     o  XVOL, sets the width of the 3D plotting volume

     o  XXRNG, sets the width of the 3D target mapping range for gridmap
        and parametric surface plots

     o  YSLICE, selects the new "yslice" plot type

     o  YVOL, sets the depth of the 3D plotting volume

     o  YYRNG, sets the depth of the 3D target mapping range for gridmap
        and parametric surface plots

     o  ZVOL, sets the height of the 3D plotting volume

     USER-INTERFACE COMMANDS:

     o  CHOOSE, displays a point-and-click menu "dialog box"

     o  INFORM, formatted multi-line input with named fields (nice!!)

     o  MSGBOX, displays text in a centred box with shadow, then WAITs

     o  NOVAL, placeholder for unspecified values in INFORM argument
        list

     LIST PROCESSING COMMANDS:

     o  ADD, adds lists element-wise (see section above)

     o  DOLIST, evals an object on multiple lists

     o  DOSUBS, evals a program or command taking arguments from a list

     o  ENDSUBS, returns the number of loops the current DOSUBS will do

     o  HEAD, first element in a list or first char in a string
        (identical to CAR in Donnelly's Tool Library)

     o  DeltaLIST, list of first finite differences of list objects

     o  SigmaLIST, sum of the elements in a list

     o  PiLIST, product of the elements in a list


     o  NSUB, returns the current list pointer value during a DOSUBS

     o  REVLIST, reverses the order of the objects in a list (like
        REVERSE in Donnelly's Tool Library)

     o  SEQ, list of results from repeated execution of an object (like
        a FOR/STEP loop but the results go into a list)

     o  SORT, sorts elements in a list into ascending order, or sorts a
        list of lists using each list's first element as the key (can be
        done with LSORT/QSORT in Donnelly's Tool Library)

     o  STREAM, executes an object on first two elements of a list, then
        again on the result and the 3rd element, etc.  Allows easy
        creation of things similar to SigmaLIST and PiList.

     o  TAIL, returns a decapitated list or string (see HEAD above)
        (identical to CDR in Donnelly's Tool Library)

     SYSTEM COMMANDS:

     o  CLTEACH, clears the 'EXAMPLES' directory created by TEACH

     o  CYLIN, sets polar/cylindrical coordinate mode

     o  FREE1, like 1 FREE (see section above)

     o  MERGE1, like 1 MERGE (see section above)

     o  PINIT, port initialize, esp. important for 4-Meg RAM card users

     o  RECT, sets rectangular coordinate mode

     o  SPHERE, sets polar/spherical coordinate mode

     o  TEACH, loads the Owner's Manual examples into a dir in HOME

     o  VERSION, returns the operating system ROM version string and a
        copyright notice, like this:


          2: "Version HP48-R"      <-- means version "R"
          1: "Copyright HP 1993"


     o  XRECV, X-Modem protocol receive (binary mode only)

     o  XSEND, X-Modem protocol send (binary mode only)

     MATH COMMANDS:

     o  LININ, tests whether an equation is linear in a given variable

     o  NDIST, normal probability density

     o  PCOV, population covariance of SigmaDAT

     o  PSDEV, population standard deviation of SigmaDAT

     o  PVAR, population variance of SigmaDAT

     o  RKF, solves initial value problem using Runge-Kutta-Fehlberg


     o  RKFERR, change in solution and absolute error using RKF

     o  RKFSTEP, next solution step with given error tolerance using RKF

     o  RRK, solves initial value problem using Rosenbrock & RKF

     o  RRKSTEP, next solution step with given error tolerance using RRK

     o  RSBERR, change in solution and absolute error using Rosenbrock

     MENU NUMBERS and KEY CODES
        Many menu numbers have changed, so software that uses # MENU or
        # TMENU may not work the same as in the HP48 S/SX.
        (Specifically, only menu numbers 0-3, 28, 30, and 42-59 are the
        same). Likewise, almost all of the shifted keycodes correspond
        to new commands and menus, which programmers must take into
        account; for example, the "RAD" key on the S/SX had the keycode
        82.2, but it's 21.2 on the G/GX.  The left-shift key, which was
        orange on the S/SX, is now purple [officially "lavender"], and
        the right-shift key which was blue on the S/SX is now green
        [officially "teal"] on the G/GX.  Also, the digit-key menus can
        be activated by both shift keys; left-shift gives the softkey
        menus like in the S/SX, but the right-shift gives the new user-
        friendly full-screen menus.  The unshifted keys remain identical
        to the S/SX, except for a cosmetic colour change to match the
        very dark green of the calculator case.

     MANUALS
        The G/GX comes with two manuals, a "Quick Start Guide" for
        beginners, and a cost-cutting, slimmer owner's manual called the
        "User's Guide" which has only 21 pages about programming, since
        HP figures that the huge majority of all 48 owners never program
        it anyway.  The power users can buy the optional "Advanced Users
        Reference Manual" (similar to the S/SX's "Programmer's Reference
        Manual") which covers programming and the many commands that are
        not mentioned in the User's Guide.  There is no "Quick Reference
        Guide" like the S/SX came with, although the case still has a
        pocket for one.

        Jim Donnelly has marketed a nice pocket guide, but it's too wide
        to fit in the case's pocket.  The User's Guide is not spiral
        bound, but is made to open fully and last a long time, since
        it's not just glued but has sewn signatures like real books, and
        is printed on quality paper.

        Another possibility is "The HP 48G/GX Pocket Guide" by Chris
        Coffin and Thomas Dick (Grapevine Publications).  It's 80 pages
        long, contains a complete command reference (with input/output
        stack diagrams), alpha keyboard description, system flag
        description, as well as examples of how to use various
        calculator features.  This guide is designed to fit nicely in
        the pocket of the HP case.

     FLAGS
        Some previously "unused" flags are now used.  They are:


     -14 Clear = end-of-period payment mode (for TVM calculations)
         Set   = beginning-of-period payment mode

     -27 Clear = display symbolic complex numbers in coordinate form
                 e.g. '(X,Y)'
         Set   = display symbolic complex numbers using 'i'
                 e.g. 'X+Y*i'

     -28 Clear = plot multiple equations like the S/SX does (serially)
         Set   = plot multiple equations simultaneously

     -29 Clear = include axes in plots (like the S/SX does)
         Set   = omit axes from 2D and statistics plots

     -30 is no longer used (it never did anything useful anyhow)

     -54 Clear = tiny matrix elements get rounded to zero
         Set   = leaves matrix elements alone


     The default setting of all these flags is Clear (as in the S/SX).

     FLAG BROWSER
        There is a System Flag browser which shows the flag number,
        shows whether it's set or clear, lets you toggle it, and shows
        in English what the current setting means.

     CHARACTER BROWSER
        While programming, if you want to type any character at all,
        press CHARS and a screenful of ASCII characters is displayed
        that you can browse with the arrow keys, and not only does the
        screen also show the ASCII code (NUM value) and even the
        shortcut keyboard key sequence (if any) for each character, but
        if you press ECHO, it will be "typed" into your program.
        There's no need any more for the alpha keyboard table.

     DIRECTORY MAINTENANCE
        Press right-shift VAR to launch a Variable Browser which is a
        complete memory manager.  You can tag multiple objects and copy,
        move, or delete them all with a single keystroke; there's even a
        Mark All and an Unmark All, like a real computer.  It's slow,
        however, and has been obsoleted by the very fast PCT library.

     FRACTIONAL UNIT POWERS
        The S/SX only handled integer powers of units correctly, but the
        G/GX can use any real number as a unit power.

     NAME PLATE
        The case has a rectangular indentation in the back like the HP
        95LX and 100LX, and it comes with an adhesive metal nameplate
        that you can get engraved with your name.

     XLIB NAMES
        All of the new commands in the GX are XLIB names, and therefore
        take 5.5 bytes in programs.  The commands common to the SX and
        GX take 2.5 bytes each, as they did in the SX.

     INPUT FORMS and CHOOSE BOXES
        Many operations have two menu types: the old SX style, and a new
        "drop-down" menu and "input forms" that have the feel of
        computer dialog boxes.  Especially useful for the HP48 beginner.

     ENHANCED PRECISION
        The internal precision of at least some of the matrix routines
        has been improved; INV gets better answers on square matrices
        than the SX did.  HP has not released information about which
        routines were improved, how, and by how much.

     IMPROVED DISPLAY
        The LCD introduced with revision M of the G/GX is easier to read
        since it has higher contrast between on/off pixels.  It has a
        slower cycle response time, however, making it difficult to use
        for rapid-motion video games or any other rapid animation.


  10.2.  Examples of INFORM, CHOOSE, and MSGBOX

  From: Jarno Peschier

  Some examples of INFORM, CHOOSE and MSGBOX on the HP48 GX. Just
  download the entire directory to your calculator and try the programs,
  change them, modify them and do everything else with them you can
  think of.

     SIMPLE:
        This program will demonstrate a simple INFORM input screen with
        3 fields (one without type restrictions, one for real or complex
        numbers and one for strings) with some additional layout. MSGBOX
        and CHOOSE (with the third parameter equal 0) are used to show
        what the results of the INFORM command are. The list the INFORM
        command returns is left on stack so you can see what it looks
        like.

     ANGLE:
        This program will demonstrate the use of CHOOSE. It lets you
        choose between the three possible angle modes (DEG, RAD, GRAD)
        and when you choose one of them, the corresponding mode is set
        by evaluating a tiny program containing the right command.

     ISOLATE:
        This program will demonstrate the use of INFORM in ways that it
        is used in the calculator itself. It is a very simple shell
        around the ISOL command (isolation of a variable from an
        algebraic). It remembers it's settings in a variable called IPAR
        and the next time the program is run this will be the default
        values of the INFORM command, so you can isolate for a different
        variable using the same algebraic you used before, without
        retyping it. MSGBOX is used for error messages.

     TYPELIST:
        This program will again demonstrate the use of CHOOSE. It
        extracts the names of all the internal types of the HP48 GX from
        ROM and shows them in a CHOOSE-box (alphabetically sorted by
        name). If you choose one of them, its TYPE number is shown in a
        MSGBOX.

     MATHQUIZ:
        This final program will demonstrate the use of INFORM with
        variable field descriptions and default/reset values. It's will
        show you 8 fields that are simple math questions for you to
        solve (addition and subtraction).  You can enter all the results
        and then you will see if your answers were correct (in a
        MSGBOX). You must fill all the fields. Hint: you can cheat by
        resetting a field (or all fields).


     %%HP: T(3)A(D)F(.);
     DIR
       SIMPLE
         \<<
           IF
     "AN EXAMPLE OF INFORM"
     { { } { } { } {
     "OBJECT:"
     "ALL OBJECTS ARE ALLOWED HERE"
     } { } { "NUM:"
     "ENTER A (COMPLEX) NUMBER"
     0 1 } { "NAME:"
     "ENTER YOUR FULL NAME"
     2 } { } { } } { 3 1
     } {
             \<< 440 1
     BEEP
             \>> (0,1)
     "JARNO PESCHIER" }
     { NOVAL 0 "N.N." }
     INFORM
           THEN DUP
     "YOU ENTERED:" SWAP
     0 CHOOSE DROP
     "The list that INFORM produced is still on the stack."
           ELSE
     "You cancelled the INFORM."
           END MSGBOX
         \>>
       ANGLE
         \<<
           IF
     "ANGLE MEASURE" { {
     "Degrees" DEG } {
     "Radians" RAD } {
     "Grads" GRAD } } 1
     CHOOSE
           THEN EVAL
           END
         \>>
       ISOLATE
         \<<
           IF
     "A VERY SIMPLE VARIABLE ISOLATOR"
     { { } { "EXPR:"
     "ENTER THE EXPRESSION"
     9 } { "VARIABLE:"
     "ENTER VARIABLE TO ISOLATE"
     6 } } { } { }
             IF 'IPAR'
     VTYPE 5 \=/
             THEN { }
             ELSE 'IPAR'
     RCL
             END INFORM
           THEN DUP 'IPAR' STO
             IF DUP
     NOVAL POS
             THEN DROP
     "You must enter an expression and a variable!"
     MSGBOX
             ELSE OBJ\->
     DROP
               IFERR
     ISOL
               THEN
     DROP2 "Error: "
     ERRM + MSGBOX
               END
             END
           END
         \>>
       TYPELIST
         \<<
           IF
     "ALL HP48 TYPES (IN ROM)"
     0 27
             FOR msg
               IFERR msg
     263 + DOERR
               THEN ERRM
               END msg 2
     \->LIST
             NEXT 28
     \->LIST SORT 1 CHOOSE
           THEN
     "That one has type number "
     SWAP + "." + MSGBOX
           END
         \>>
       MATHQUIZ
         \<<
           IF
     "A SIMPLE MATH QUIZ"
     1 8
             FOR i "'"
     RAND 100 * IP +
               IF RAND
     0.75 <
               THEN "+"
               ELSE "-"
               END +
     RAND 100 * IP + "'"
     + "ENTER RESULT #"
     i + 0 3 \->LIST
             NEXT 8
     \->LIST DUP
             \<< \-> X
               \<< X HEAD
     2 OVER SIZE 1 - SUB
     "=" + X 1 ROT PUT
               \>>
             \>> DOLIST
     SWAP
             \<< \-> X
               \<< X HEAD
     OBJ\-> EVAL
               \>>
             \>> DOLIST 3
     ROLLD { 2 5 } 4
     PICK { } INFORM
           THEN
             IF DUP
     NOVAL POS
             THEN DROP2
     "You didn't fill all the blanks."
             ELSE
               IF SAME
               THEN
     "All answers were correct!"
               ELSE
     "Not all answers were correct."
               END
             END MSGBOX
           ELSE DROP
           END
         \>>
     END


  10.3.  Some useful LIBEVALs

  From: Joe Horn

  Note well: backup memory before using any of the following!  LIBEVAL
  can clear memory if used incorrectly.  Warning to the clueless:
  LIBEVAL, NOT SYSEVAL!!!  If you don't know what a "bint" is, don't use
  the ones that mention bints.

  Example usage: "OUT OF RANGE Try Again" #B0091h LIBEVAL.  Try it!


       -----------------------------------------------------+----------
       Function                                             | LIBEVAL
       -----------------------------------------------------+----------
       Displays message box with grob                       | #B1000h
       CMD  last command window                             | #B2000h
       CHARS application                                    | #B2001h
       MODES application input form                         | #B41C1h
       flag browser  (returns t/f to level 1, just drop it) | #B41CFh
       MEMORY application  (aka variable browser)           | #B41D7h
       SOLVE application choose box                         | #B4000h
       solve equation input form                            | #B4001h
       solve difeq input form                               | #B4017h
       solve polynomial input form                          | #B402Ch
       solve linear systems of equations input form         | #B4033h
       solve TVM input form                                 | #B4038h
       PLOT input form                                      | #B4045h
       SYMBOLIC application choose box                      | #B4113h
       integrate input form                                 | #B4114h
       differentiate input form                             | #B4122h
       Taylor polynomial expansion input form               | #B412Bh
       Isolate a variable input form                        | #B412Dh
       solve quadratic input form                           | #B4130h
       manipulate expression input form                     | #B4131h
       TIME application choose box                          | #B4137h
       Set alarm input form                                 | #B4138h
       Set time and date input form                         | #B415Bh
       Alarm browser   (aka alarm catalog)                  | #B416Eh
       STAT application choose box                          | #B4175h
       single-var stat input form                           | #B4176h
       frequencies input form                               | #B417Dh
       fit data input form                                  | #B417Fh
       summary stat input form                              | #B418Fh
       I/O application choose box                           | #B4192h
       Send to HP48 input form                              | #B4193h
       Print input form                                     | #B4197h
       Transfer input form                                  | #B41A8h
       Get from HP48  (immediate)                           | #B50FFh
       recalls the contents of the reserve variable Mpar    | #E4012h
       -----------------------------------------------------+----------


       LIBEVAL : stack diagram / what it does
       -------   -----------------------------------------------------------
       #B0091h : $ --> makes a message box with an alert symbol in it
       #E0044h : $ --> displays a title line, top center (follow with
                 1 FREEZE if you want it to stay there after program ends)
       #B2000h : launches the Last Command choose-box
       #B2001h : launches the CHARS application; returns nothing if user does
                 not press ECHO
       #B2002h : launches the CHARS application; returns "" if user does not
                 press ECHO
       #B41CFh : launches Flag Browser; leaves a True or False on stack, so
                 follow this LIBEVAL with a DROP.
       #B50A3h : --> current time as hour, min, sec separately, plus an XLIB
                 that represents AM/PM/24-hr (just DROP it)
       #B50A4h : hh.mmss --> hh mm ss xlib (the xlib represents AM,PM, or
                 24-hr mode; just DROP it)
       #B50A6h : --> current date as month, day, year (always that order, and
                 a two-digit year)
       #B50A7h : mm.ddyyyy (or dd.mmyyyy) --> month, day, yr
       #B50A9h : #month #yr --> #days_in_that_month (inputs and output are
                 bints; year is two digits, interpreted as between 1991 &
                 2090 only)
       #B50AAh : #yr --> %0.00yyyy (input is two-digit bint interpreted as
                 between 1991 and 2090; output is a real number)
       #B50ABh : #mon #day #yr --> #day_of_week (inputs & output are bints;
                 year is two digits interpreted as between 1991 & 2090;
                 Sunday is #7; if you're in DMY mode, then the input order is
                 #day #mon #yr)
       #B50B2h : --> { 1 2 3 ... 59 } (not very fast)
       #B50B3h : --> { 1 2 3 ... 10 } (very fast)
       #B50B4h : --> { 0 1 2 ... 23 } (very fast)
       #B50B9h : --> { " 1 January" " 2 February" ... "12 December" }
       #B50D5h : --> number of alarms currently set (as a bint)
       #E3063h : hxs --> grob (this is an RLL packed-grob uncompressor, used
                 by EQ LIB and MINEHUNT; for example, try this:
                 #E202Bh LIBEVAL 3 GET #E3063h LIBEVAL PICT STO PICTURE)
       #E202Bh : the first of the packed EQ LIB grobs (see above)
       #E2069h : the last of the packed EQ LIB grobs (see above)
       #E7039h : MINEHUNT packed grob (left screen border)
       #E703Ah : MINEHUNT packed grob (right screen border)
       #E801Eh : obj --> obj T/F (tests whether object is in temporary memory
                 or not; returns System-RPL True or False)


  11.  Appendix C: Details of Bugs

  11.1.  The EquationWriter Bug

  From: Joe Horn


     Rev E Behaviour
        Clear flag -53 first (the Precedence Flag).

        On a Rev E, put '((1+2)/(3+4))^5' on the stack and press down-
        arrow.  You'll see:


                 5
          / 1+2 \
          | --- |                         (A)
          \ 3+4 /

     which is as it should be.  But now press [orange-shift] [+]; see
     the message "Implicit () off" momentarily; press [left-arrow] (not
     backspace), then press the [EXIT] softkey.  The expression gets
     mangled into this:


              1+2
          -----------                       (B)
                (5)
           (3+4)


     which is not equal to expression (A) above!  Bug, yes?  Press ON to
     abort the process.

     Now set flag -53, then repeat the above procedure.  First you see:


                 5
          / 1+2 \
          | --- |                         (C)
          \ 3+4 /


     which is the same as (A) above; but continuing as before, you see:


                   (5)
          /  1+2  \
          | ----- |                       (D)
          \ (3+4) /


     which is equal to the original.  Thus the bug can be worked around
     by keeping flag -53 set (not a pleasant solution).

     Rev J Behaviour
        Major difference: after pressing down-arrow, Rev J goes directly
        into graphic mode, so you have to press ON and then EXIT to get
        into the equation editor (which Rev E goes directly into).  But
        that's petty cash compared to the following big change.

        The same sequence of operations, first with flag -53 clear, then
        set, exactly as detailed above, yields these four displays in a
        Rev J:


                   5
          / (1+2) \
          | ----- |                       (A')
          \  3+4  /


     (notice the extra parentheses?) and then:


              5
     / (1+2) \
     | ----- |                       (B')
     \ (3+4) /


     which is equal to (A'); nothing at all like expression (B) above!
     and then:


                   5
          / (1+2) \
          | ----- |                       (C')
          \  3+4  /


     which is the same as (A') above; and then:


                   5
          / (1+2) \
          | ----- |                       (D')
          \ (3+4) /


     which is also equal to (A').  No bug in Rev J.

  SUMMARY: Rev A-E have a bug in the EquationWriter that can mangle
  expressions if flag -53 is clear (the default) and if "Explicit Paren-
  theses" mode is toggled.  This bug has been fixed in Rev J.

  Unfortunately (as you can see above) Rev J always puts parentheses
  around polynomial numerators.  It is therefore impossible to use the
  ->GROB command on a Rev J to create a GROB that looks like expression
  (A) above; the simplest that can be had is expression (A').

  Another minor change, while I'm at it: Rev A-E don't change the menu
  when you press REPL; Rev J automatically flips to the appropriate
  RULES menu.


  11.2.  Rotation Rate to Angular Frequency Conversion Bug


     About the Bug:
        From: Wlodek Mier-Jedrzejowicz <wacm@doc.ic.ac.uk>

        There is a rotation rate conversion bug in the HP48 G/GX which I
        have not seen reported here before, so after discussion with the
        folks at Corvallis I am posting this description. Warning: it is
        159 lines long!

        First - an example. Put the unit object 60_rpm in level 2 and
        the unit object 1_r/s in level 1, then execute the command
        CONVERT.  You are asking the HP48 to convert a rotation rate of
        60 revolutions per minute into an angular frequency in radians
        per second. 60 rpm is 1 revolution per second, or 2pi radians
        per second.  No HP48 G/GX will give this answer!  Not everyone
        uses rpm or is even aware of the existence of this unit - it is
        one of the extra units in the UTILS menu of the Equation Library
        - so here is a second example - add 2pi radians per second to
        one Hertz.  Put 6.2832_r/s in level 1, 1_Hz in level 1, and add.
        You are adding an angular frequency of two pi (one cycle) per
        second to a rotation rate of one per second, so the result
        should be a frequency of two Hertz.  On an HP48 S/SX that is the
        answer.  On an HP48 G/GX it is not.

        When units are converted, by CONVERT, or during arithmetic on
        unit objects, the level 2 object is first turned into "base
        units", and then the result is converted into the units of the
        level 1 object.  On the HP48 S/SX, the "base unit" of angles is
        one rotation (or a "unit circle" or a revolution or a cycle).
        So, the angle unit of rpm (a revolution) or of Hz (a cycle if Hz
        is treated as a rotation rate) is already in base units -
        conversions to angles involving rpm and Hz automatically work
        correctly.  On the HP48 G/GX, the "base unit" of angles is the
        current angle mode (DEG, RAD or GRAD) - so any conversion from
        rpm or Hz (or any formula which works in cycles, rotations,
        revolutions, unit circles) to angles should be preceeded by a
        conversion from the unit circle to the current angle.
        Apparently no-one noticed this would be necessary, because it
        all worked automatically on the HP48 S/SX.

        So, when you convert 60_rpm to units of _r/s, an HP48 G/GX
        converts not 60 rotations but 60 "base angle units" per minute
        to radians/second. In RAD mode, you get 1 radian per second. In
        DEG mode you get 1 degree per second, and in GRAD mode you get 1
        grad per second (in each case expressed in radians). That's
        three different answers, none of which is correct! Exactly the
        same happens if you convert 1_Hz to angles per second, and the
        inverse mistake is made if you convert angles per time to cycles
        or rotations divided by time.

        I first learned of this bug from a member of HPCC (the British
        club for users of HP handhelds), Peter Embrey. He describes his
        troubles in articles in the first two 1994 issues of our club
        journal, DATAFILE (in Volume 13 number 1 pages 12 to 14 and
        V13n2p6). He was calculating the energy stored by a flywheel -
        given by the formula (1/2)*I*omega^2 and after a time he decided
        the answers had to be much too big when he CONVERTed from
        kg*m^2*(r/s)^2 to W*h on an HP48 GX.  It turns out that (r/s)
        are the correct units to get the right answer, but the GX was
        converting to degrees per second as it was in DEG mode, so his
        answer was too large by a factor of (360/2pi)^2 - a factor of
        about 3,300. In this case, his HP48 SX was not much better,
        since it converted from radians to unit circles. The way to get
        the correct answer is to use an HP48 G or GX in RAD mode - or to
        divide out the radians from the formula before using CONVERT.
        This is not yet a bug, but needs as much care as does use of
        temperature units on the HP48. But when Peter tried to deal with
        the problem by working in rpm, he came upon the bug described
        above. My thanks to Peter for putting me on the trail!

        Apparently this bug not been reported before - at least my
        friends in HP tell me that it was not on their list of known
        problems until I told them of it. (This means it is not fixed in
        the new revision R.) Why not - does everyone know about it and
        work around it without thinking to tell anyone else? Or does no-
        one use their HP48 to do calculations on rotating bodies - or do
        most people do calculations with rotating bodies in such a way
        that they do not encounter this problem? Could there be hundreds
        of students and engineers out there calculating and designing
        things on their HP48 G/GX and getting wildly inaccurate results?
        Has anyone built a disk drive or a jet engine which rotates far
        too fast and will disintegrate because of this? No, of course
        not, all engineers know that any design calculation absolutely
        must be repeated on two entirely separate calculators or
        computer programs! :-| Maybe some students have lost marks in
        exams because of this though - but please, this is not intended
        to restart the discussion as to whether calculators should be
        allowed in exams!

        I want to underline again that apparently no-one has reported
        this before - which must mean that few people have been affected
        by it. It is therefore not a good reason to throw away your HP48
        G/GX or get on a high horse and demand that HP replace your HP48
        G/GX - but I think it is important that people be warned so they
        can take appropriate avoiding action. The rest of this message
        goes into more detail - if you never worry about rotation
        calculations then you can safely ignore the rest - though you
        might find it interesting, so don't stop yet :-)

        One way to avoid this would be to add a new unit to the HP48 -
        call it what you like - the "cycle" or "rotation" or
        "revolution" or "unit circle". As I wrote above, this is already
        implied in the HP48 S/SX; to see this on an HP48 S/SX, put 360
        degrees in level 1 and execute UBASE - the result is 1, meaning
        that 360 degrees are equivalent to one base unit of angle
        measurement, but that there is no named HP48 unit corresponding
        to this. In contrast, UBASE on an HP48 G/GX considers the base
        unit of angle measurement to be the radian, even though CONVERT
        behaves as though the base unit is the current angle mode. There
        appear to be two different norms for base angle units on the
        HP48 G/GX!

        The whole subject gets very little mention in HP's manuals. In
        the original HP48 SX manual (two volumes, spiral bound), the
        section on "Dimensionless Units of Angle" in chapter 13, on page
        198, warns the reader about the danger of using dimensionless
        units and states how angle units and scalars are treated. In the
        later HP48 S and HP48 SX manual (one volume), the same warning
        is given in "Converting Dimensionless Units of Angle", on page
        13-12. The HP48 G Series User's Manual, in "Converting Angular
        Units" on page 10-7, says that conversion will interpret a
        scalar according to the current angle mode setting. (A scalar is
        a pure number with no units.)

        For a detailed description, look in the HP48 S/SX edition of
        "HP48 Insights Vol II", section 21.4.3. This book is written by
        Dr Bill Wickes, who was the design team leader of the HP48 SX,
        and who wrote the "Insights" books largely to provide the sort
        of explanations and details that get left out of manuals. A good
        explanation of angle units is exactly the sort of thing one can
        find there! He explains the pitfalls and unavoidable
        contradictions of working with angles in the HP48 units system
        and points out that the HP48 S/SX make the somewhat arbitrary
        choice of using 2pi as the base unit of angles, thereby making
        conversions between angles per time and Hertz work correctly.

        Maybe no-one on the HP48 G/GX team read this while they were
        making changes from the HP48 S/SX! Why did they change the base
        unit at all?  Most likely they were trying to deal with another
        contradiction: the units system lets you add pure numbers to
        angles, since both are dimensionless. If you add the number 1 in
        level 2 to the unit object 0_r in level 1 on an HP48 S/SX, the
        number 1 is treated as 1 base unit, or 2pi radians, and the
        result is 6.2832_r - but if you take the SIN of the number 1
        instead, it is not treated as 2pi, but as 1 unit of the current
        angle mode. The change made on the HP48 G/GX does resolve this
        contradiction, but at the cost of introducing the bug described
        above.

        As mentioned, a way to resolve the problems involved would be to
        add the angle unit "cycle" explicitly to the HP48 units system.
        Hz would then be treated as cycles per second when used in
        calculations involving rotations - rpm would be treated as
        cycles per minute, and conversions would go from cycles to the
        appropriate angle units. This suggestion was made by Peter
        Embrey in his articles, and the folks at HP accept that this is
        a good solution - but they have not implemented it yet. In the
        meantime, be very, very careful when converting between units of
        rotation rate and units of angular frequency. I would urge
        everyone who does not yet have a copy of Insights II to buy one
        and read the relevant section - maybe that will even entice Bill
        Wickes into publishing his long-awaited HP48 G/GX version of the
        book!

        I have not yet mentioned solid angles. In principle there should
        be no problem - on both the HP48 S/SX and the HP48 G/GX the base
        unit of solid angle is a "unit sphere", or 4pi steradians. On
        the HP48 S/SX you can add the pure number 1 to 0_sr and get
        12.5664_sr (4pi steradians). The HP48 G/GX manuals imply that
        exactly the same should happen, but on my (version L) HP48 GX
        this gives the error message "Inconsistent Units".  This is yet
        another undocumented difference between the Series S and Series
        G but at least it is no bug!

        Apologies for making this description so long, I hope most
        people will agree that a subject like this deserves a careful
        description! For my next trick - some details on the HP48 Random
        Number Generator.


     Addition Insight:
        From: Eric Haas <EHaas@ix.netcom.com>

        Note: The < symbol below is actually the angle character.

        The angular conversion bug is actually in the definition of the
        rpm unit.  If you put 1_rpm on the stack, and type UBASE, you
        get 1.66666666667E-2_1/s.  Notice that there is no angular unit
        in the definition. If the rpm unit is instead defined as 6_</s,
        all conversions to and from rpms will work just fine. As an easy
        work-around, define the unit RPM as 6_</s and use that instead
        of the built-in unit.

        If desired, one could also define the unit HZ as 60_rpm or
        360_</s.  However, as Hz is sometimes used to describe things
        other than rotation rates, such a definition would not be
        appropriate for all circumstances.


  12.  Appendix D: Hardware Additions

  12.1.  How to Make a Serial Cable

  From: Frank Vorstenbosch <prompt@xs4all.nl> Revised by: Andrew Chen

  Now that you have your HP, you probably want to tap the tremendous
  amount of programs out there.  But how do you do this?  You need an HP
  to PC link.  You can buy one, but they tend to be fairly costly.  Or
  you can build your own.  The process requires the following parts:

  Required Parts:


  o  Soldering iron and flux

  o  RS232-9 or RS232-25 shield (serial port shield)

  o  RS232-9 or RS232-25 female connector (serial port connector)

  o  4 pin HP connector, with sockets spaced 2 mm (NOT 0.1") apart

  o  Some copper wire

  Of the above list of parts, most are pretty easy to acquire, and you
  should be able to find them at your local electronics store.  However,
  the 4 pin (i.e. male) HP connector can be a bit harder to find.

  If you happen to have a broken floppy drive, hard drive, or CD-ROM
  audio cable lying around, look inside and see if you can find a
  connector there that will fit the HP48.  Do not use a 0.1" connector,
  as this will damage the pins on your calculator.


     HP Connector
        The HP connector part of the cable will be the most frustrating
        part of the link.  The reason is that you will probably not be
        able to find these at your local electronics store, but you
        should you should find everything else there.  Instead, you can
        either find the connector at used computer stores or you can
        create the link yourself.


        Easy Way
           Because the former is much easier, I will give you some tips
           on where one can find the connecter.  First, check your
           yellow pages and look under "computer".  You will find a lot
           of stores, but look specifically for "computer repair" or
           "computer parts".  Call these stores asking for a "CD-ROM
           audio cable".  If the store carries these cables, go to the
           store and ask to see the requested cable.

           What you should see is a cable with two ends, each with a 4
           socket connector.  One end should be spaced a bit larger than
           the other, and this one will not fit into the HP's pins
           (don't press too hard, or else you will bend the connector
           pins).  The other side should fit like a charm.  Don't be
           worried about that there are only 3 sockets.  This is fine
           because the empty one is a ground.  Once you have this cable,
           cut off the unusable end, and go to the PC connector section.


        Hard Way
           If are unable to find a place that carries CD-ROM audio
           cables, or you prefer to make your make, it is possible to
           build the connector yourself.  What you can do is buy IC
           sockets from a local electronics store.  You can usually find
           them in packs of 8 or more.  These IC sockets will be bound
           together in a hard plastic shell, which also places at
           unusable intervals.  Therefore, it is necessary to strip the
           IC sockets out of the hard plastic shell (don't worry too
           much about damaging them, the IC sockets are fairly durable
           and you have 8 of them).

           Next, solder a 'fork' from thin rigid metal wires, to hold
           the four IC pins spaced at exactly 2 mm while you glue them
           together with superglue.  Glue a plastic 'handle' to the four
           IC pins to be able to remove the connector from the HP48.
           You can also indicate the top side of the connector on this
           handle.

           Note that the hole in the HP48 in which the connector should
           go is not symmetrical; the pins are nearer to the top of the
           calculator than the bottom, and you can use this to make it
           difficult to insert the connector the wrong way up.

           With that done, you can proceed on to the PC side of the
           connector.


     PC Connector
        The PC side of the connector is much simpler than the HP side.
        All you have to do is make a standard serial connector with the
        parts you bought.  However, don't do it yet because you need to
        solder the wires from the HP connector into the back of the
        serial connector first.


     Making the Connections
        Now that you have the two sections done, you can begin making
        the connections for the actual link.  Starting with the HP side,
        put in the connector and mark the top as "UP".  If you have a
        CD-ROM audio cable with one socket missing, make sure that the
        empty socket connects to pin 1:


           Connector on HP48         Connector to HP48
                ______                     ______
                |....|                     |oooo|  <-- First is
                \____/                     \____/       null
            pin 1   pin 4              pin 4   pin 1


     If you made the HP connector the hard way, you have to solder the
     ends of the IC sockets to long pieces of wire, which will
     eventually connect to the serial connector on the PC side of the
     cable.

     With these wires done, you must solder the individual wires into
     the proper places on the PC side.  Use this table of pin
     connections:


          HP to PC cable

          HP48 | RS232-9 | RS232-25
          -----+---------+----------
            1  | shield  |  shield
            2  |    2    |    3
            3  |    3    |    2
            4  |    5    |    7


     You can use either a 9 or a 25 pin female sub-D socket for the PC-
     side of the cable:


        9-pin RS232                 25-pin RS232
       connector (F)                connector (F)

     pin 5       pin 1    pin 13                     pin 1
       -------------         ---------------------------
       | o o o o o |         | o o o o o o o o o o o o |
        \ o o o o /           \ o o o o o o o o o o o /
         ---------             -----------------------
      pin 9     pin 6      pin 25                   pin 14


     Use flexible 4-wire cable to connect the four contacts of your HP48
     connector to the PC connector.  Pin 1 of the HP48 should be
     connected to the metal shield of the RS232 connector.  Usually it
     is not easy to solder this shield; first scratching the shield bare
     (it has some kind of coating) using a screwdriver or a file will
     help.  If this doesn't work, simply leave pin 1 of the HP48
     disconnected.  Note that pins 2 and 3 of the RS232 connector must
     be swapped when you use a 25-pin connector.

     Before connecting the completed cable to your HP48, check for
     short-circuits using an ohmmeter or multimeter set to ohms or
     "diode test".  The HP48 has a built in serial loop back test that
     can be used to test the serial cable (see the question regarding
     the ON-KEY combinations).

     After you are done, close the shield and connector, and put in all
     the screws.  You should now have a HP<-->PC link, which functions
     on COM (serial) ports.


     Using the Link
        With the link finished, it is now ready to be tested.  Download
        some programs (such as those in the Best Program List) that you
        wish to try.  At some point you should go to
        <http://www.columbia.edu/kermit/> to obtain the version of
        Kermit that suits you best.

        However, if you have an alternate communications program (for
        example, Windows 95 comes with HyperTerminal which you can use)
        you can delay downloading Kermit.  However, it is a highly
        recommended to obtain because certain programs for the HP48 use
        special features in Kermit (such as server mode) not available
        in other communications programs.

        With this done, you can begin the actual transfers.  Start your
        communications program, and set the port to COM1 (or whatever
        your link is plugged into).  In Kermit, you would type "SET PORT
        COM1" and in HyperTerminal you would set the dialog box with the
        choice of what modem you want to use to "Direct to COM1".

        Then change the speeds of the ports to 9600.  In Kermit, type
        "SET SPEED 9600" and in Hyperterminal click on Advanced.

        On the HP, go to I/O, and go to Transfer.  Set the calculator to
        Wire, 9600 baud, and Kermit (or X-Modem, if you using it
        instead). Then, get ready for to receive a file.  Note that X-
        Modem is much faster than Kermit in most situations, especially
        in long transfers.  However, it is not available built-in on the
        S/SX.

        On the PC start sending, and on the HP, start receiving.  You
        should see the transfer arrow on the upper right of the screen
        on the HP, and it should be flashing.  On the PC, you should see
        a progress indicator to show how much of the file has been
        transferred.

        When the transfer is finished, check that you received what you
        expected.  If it what you expected, your HP<-->PC link works!


     HP to HP Cable
        If you want to use 9600 bps communication between two HP48s,
        then make two HP48 connectors and simply connect the two,
        swapping pins two and three.


          HP to HP cable

          HP#1 | HP#2
          -----+-----
            1  |  1
            2  |  3
            3  |  2
            4  |  4


     Warranty, Disclaimer, etc...
        Although the serial interface of the HP48 is protected
        internally, it is possible to damage the calculator when a wrong
        connection is made.  I am not responsible for any errors in this
        file, or for any mistakes you may make.

  From: Deborah Lynn Williams

  I made an HP48 link out of four pieces of speaker wire and serial port
  plug.  The wiring of the plug is available above.  The connection to
  the HP plug is the difficult part.

  I took 4 pieces of stranded speaker wire and cut them so that the wire
  and the insulation were even.  I then took a paper clip and pushed it
  into the this open end, making a space between the wire and the
  insulation.  I then had to trim some of the strands that were sticking
  out.  I then just pushed this onto the pins in the HP48 port.  It
  isn't a very strong connection, but it works fine if you don't jostle
  it.

  The other ends of these speaker wires I connected to the serial plug.
  Just remember to label which wires go to which pin, or make them all
  different lengths.

  From: John Cutter

  Another cheap source for cables is the common serial mouse for PC-
  compatibles.  I had a cheap one on which the button gave out after 2
  weeks of use, so I opened it up.  It had a serial 9 pin cable that
  disappeared into the mouse.  Once open, there was a 4 pin 2 mm
  connector plugged into the mouse's circuit board.  All I had to do was
  reverse two pins inside the connector, and it's been working fine
  since.  I also noticed that Logitech mice have 6 pin 2 mm connectors,
  which could also be adapted.  No soldering or crimping here!


  12.2.  Using a modem with the HP48

  From: Diego Berge

  My purpose here is to explain in some detail the steps you need to
  follow to be able to transmit data via modem with the HP48.  Another
  related document is
  <http://www.freeweb.org/freeweb/enrico/hp2modem.htm> by Enrico Carta.

  In order to successfully connect your HP48 calculator to a modem, the
  first thing you need is a 'Null Modem Cable'.  A null modem cable is
  like a regular serial cable, except that two of its lines are crossed.

  You might wonder: So why is it different connecting to a PC than
  connecting to a modem?  Well, data communication devices can be
  classified in two groups: Devices which GENERATE or RECEIVE
  information, and devices which merely TRANSMIT information.  The
  former are called Data Terminal Equipment (DTE), PCs are an example of
  DTE; the later is called Data Communication Equipment (DCE), and are
  primarily modems.  Now, when PCs were designed, it seems like they
  didn't think somebody would ever want to hook two DTEs directly, as a
  result, in a typical PC all we have (besides the parallel printer
  port) is an RS-232 port, which is intended for connecting a DCE.  So
  when a machine wants to connect to a PC, its port must be that of a
  DCE, even if it otherwise acts as a DTE.  Within that class of hybrids
  fall HP48s, Psions, some (or most?) serial printers, mice, and a long
  etcetera.

  Remember, the RS-232 communication scheme is:


       DTE <--- DCE === DCE ---> DTE


  If you want to  link two DTE together, you must 'simulate' a DCE;
  that's what a Null Modem Cable is for.  It's called 'Null' because it
  (the modem) does not actually exist, and 'Modem' because it acts like
  if there was one.  To build a Null Modem Cable for the 48, assuming
  that you already have a regular cable, you'll need two MALE RS-232C
  connectors, at least one of which must be a DB-9 (9-pin), and a short
  piece of mouse cable or similar (some 3 inches should do) (If you
  don't have a regular cable, I recommend that you get one).  The wiring
  must be as shown here:


                CONNECTOR 'A'                             CONNECTOR 'B'
                                                 pin#:      3   2   7     (DB-25)
       pin#:      2   3   5                      pin#:      2   3   5     (DB-9)
       name:     TX  RX  GND                     name:     TX  RX  GND
                  |   |   |                                 |   |   |
                  |   |   |                                 |   |   |
                  |   |   +---------------------------------|---|---+
                  |   |                                     |   |     ( <<< and
                  |   +------------------>>>----------------+   |      >>> show
                  |                                             |  direction of
                  +----------------------<<<--------------------+          data )


  The pin number should be embossed near the pin itself in the
  connector.

  Once the physical part is done, which in most cases will be the most
  critical, you're ready to try out your brand-new, state-of-the-art,
  $2.25 null modem cable.  Plug it between your regular HP48 cable and
  your modem, turn the modem on (please don't forget this part :), and
  on the 48 type in:


       [RightShift]+[""] [alpha] [alpha] AT [ENTER]
       13 [LeftShift]+[CHARS] [CHR] [+]


  In stack level 1 you should have (# is a little black square):


       1: "AT#"


  Now type:


       [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT] [BUFLEN] [DROP] [SRECV]


  you should get:


       2: "AT###OK##"
       1: 1


  If this test goes wrong, try two or three more times.  If it still
  fails, check your cable(s), check that the 48 can transmit and receive
  to/from the PC, do the same with your modem.  And when everything else
  has failed anyway, connect your modem to the PC, crank up a terminal
  program (as Terminal / Hyperterminal, or Kermit's 'Connect' command),
  and type:


       AT&D0 [ENTER]


  the modem should respond:


       OK


  This tells the modem to ignore the DTR signal from the host, which the
  48 can't supply.  Try again with the calculator, if it works, go back
  to the terminal and type:

       AT&W0&Y0 [ENTER]


  to save the current modem configuration as default.  If it has not
  worked so far, I can't help you.

  Assuming you've got it to work, now all you have to do is learn a few
  modem commands to dial and, possibily, hang up.  In general, modem
  commands start with the two-character sequence 'AT' (no quotes) and
  end with a single <CR> character (dec 13), <LF> is optional.

  To dial a number use:


       ATDT12345<CR>


  where 12345 should be replaced by the actual number.  For example:


       [RightShift]+[""] [alpha] [alpha] ATDT0800890011 [ENTER]
       13 [LeftShift]+[CHARS] [CHR] [+] [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]


  dials the AT&T Direct access number for the UK.

  If your line is not connected to a digital switchboard, you may need
  to dial by pulses, then you should use instead:


       ATDP12345<CR>


  Next thing you'll probably ask is: 'How do I know that I'm connected?'

  If the modem has successfully established a connection, it should
  respond in most cases with a message like:


       CONNECT 9600/V34/LAPM/V42BIS/9600:TX/9600:RX


  or simply "1" if its not in the default verbose mode. Also, if the
  modem has a 'CD' indicator, it'll usually light up.  To find out via
  the calculator whether it's connected or a problem has occurred, use
  the following keystrokes:


       ( [LeftShift]+[I/O] [NXT] [SERIAL] )
       [BUFLEN] [DROP] [SRECV]

  repeatedly until a non-empty string appears in level 2.  Some common
  messages are:


       verbose:         non-verbose:

       CONNECT                    1
       NO CARRIER                 3
       ERROR                      4
       NO DIALTONE                6
       BUSY                       7
       NO ANSWER                  8
       DELAYED                   24


  Once you get the CONNECT message, you're ready to send any data you
  want to the remote host as you'd usually do.  I personally use Kermit
  this way when I'm not in the office or at home.

  Finally, when you're done you'll want to hang up the line.  The
  simplest way is turn the modem off, which I recommend.  But if you
  want to instruct the modem to hang up, the process usually is:

  (wait at least 1 sec without sending any data)


       [RightShift]+[""] [alpha] [alpha] +++ [ENTER]
       [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]


  (wait at least 1 sec without sending any data)


       [RightShift]+[""] [alpha] [alpha] ATH [ENTER]
       13 [LeftShift]+[CHARS] [CHR] [+] [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]


  Note, however, that this, as most of what I have said here about modem
  commands, might vary depending on each modem's particular brand, model
  and configuration.  You may need to read your modem's manual for more
  details.

  Disclaimer: As you'd expect, I take no responsibility for anything you
  may break, twist, cut, slice, burn, hurt, or otherwise damage while
  following these instructions.


  12.3.  Additional Information on the HP48 and RS-232

  From: John Meyers

  You can't connect the HP48 to anything else until you have first
  plugged in its cable, which finally brings the HP48's serial
  connections out to a DB9 connector.  At that point, the HP48,
  including its attached cable, is clearly configured as DCE (the same
  as a modem), so you need a "crossover" (such as a "null-modem
  adapter") to connect the HP48 to a modem.
  12.4.  Using Non-HP RAM Cards

  If you use RAM cards that are NOT designed for the HP48, it is
  possible to severely damage your HP48.  If you want to be safe, you
  should only use RAM cards designed for the HP48.

  Here is an edited discussion from comp.sys.handhelds.


  From steveh@hpcvra.cv.hp.com Fri Mar  1 17:00:00 1991
  From: steveh@hpcvra.cv.hp.com (Steve Harper)
  Date: Thu, 10 May 1990 22:46:09 GMT
  Subject: RE: HP48 SX Memory Card Pricing
  Organization: Hewlett-Packard Co., Corvallis, OR, USA


  There has been a substantial amount of comment regarding the memory
  cards for the HP48 SX and their prices.  My purpose in this response
  is not to attempt to justify any particular price, but rather to
  present the technical reasons why there is a substantial price
  difference between the memory cards and other types of expansion
  memory for PC's, for example, with which users are probably more
  familiar.

  Some users have correctly pointed out that the memory in the cards is
  static RAM rather than dynamic RAM commonly used in PC's.  Dynamic RAM
  uses one transistor and a capacitor for each bit of memory whereas
  static RAM requires either four transistors and two resistors, or six
  transistors.  The net result is that an equivalent amount of static
  RAM is much larger and therefore much more expensive than dynamic RAM.
  The advantage is that static RAM doesn't need to continually be
  running and drawing current (refresh cycles) to retain the contents of
  memory.

  In addition, the static memory used in the cards is not just any
  static memory, but is specially processed and/or selected for very low
  standby current.  This allows the backup battery in the card to keep
  memory alive for a very long time, rather than requiring the user to
  replace it every few months.  The special processing and/or special
  testing to select low current parts adds to the already higher cost of
  the static RAM chips.

  The standard molded plastic DIP package used for most integrated
  circuits, including memory chips, is relatively inexpensive because of
  its simplicity and the huge volumes.  Unfortunately, these packages
  are too large to put into a memory card.  Therefore, the card
  manufacturer mounts the individual silicon memory chips directly on a
  special thin PC board together with the memory support chips.  Because
  multiple chips are being placed in a single hybrid package in a
  special process which has lower volume, yields are lower and this
  again causes the cost to be higher.  Indeed, the yield becomes
  exponentially worse as the number of chips and interconnections
  increases in such a packaging process.

  In addition to the memory chips themselves, two more integrated
  circuits and several discrete components are required for power and
  logic control.  A bipolar technology chip senses the external voltage
  and switches the power to the chips from the internal keep-alive
  battery as needed.  A CMOS gate array chip protects the memory address
  and data lines from glitches/ESD when the card is not plugged in.
  This chip also generates the proper enabling signals when there are
  multiple memory chips in the card, as is presently the case with the
  128 Kbyte RAM card.  These chips must be designed for extremely low
  current, just as the memory chips are.

  In addition to the battery and the battery holder, the other
  mechanical parts are important, too.  The molded plastic frame holds
  the PC board and provides the foundation for the metal overlays and
  the shutter-and-springs assembly which protects the contacts from ESD
  and from contaminants.  The write-protect switch is also an important
  feature.  It is quite expensive for the manufacturer to make the tools
  necessary to fabricate each of these parts as well as the tools to
  assemble and test the complete card.  While the volume of memory cards
  is relatively low this tooling cost represents a significant part of
  the cost of each card.

  Admittedly, there are other alternatives, such as those presently used
  in PC's, to provide a memory expansion capability.  To provide that
  kind of expansion would require the calculator to be much larger than
  it is and possibly more expensive.  This is clearly very undesirable.

  Other features that were felt to be essential were the ability to
  distribute software applications and to share and archive/backup user-
  created programs and data.  Other expansion alternatives  do not
  provide these important benefits.  The I/O capabilities of the
  calculator provide these features only to a limited degree.

  One other item bears repeating here: Memory cards for use in the
  calculator will clearly indicate that they are for use with the HP48
  SX.  Other memory cards exist which are mechanically compatible with
  the HP48 S, but these cards cannot be relied upon to work electrically
  in the calculator.  The HP48 SX cards are designed for a lower supply
  voltage range.  Use of the other cards may cause memory loss, and
  under certain circumstances may even damage your calculator
  electrically.


  From steveh@hpcvra.cv.hp.com Fri Mar  1 17:00:00 1991
  From: steveh@hpcvra.cv.hp.com (Steve Harper)
  Date: Fri, 11 May 1990 16:52:07 GMT
  Subject: Re: Memory Card: Give Us True Facts!
  Organization: Hewlett-Packard Co., Corvallis, OR, USA


  My previous statement that under certain circumstances the calculator
  may even be damaged electrically is not a ploy.  If the calculator's
  internal power supply voltage happens to be near the low end of the
  range, say 4.1 V, and the voltage at which the card's voltage control
  chip shuts it down happens to be near the high end of its range, say
  4.2 V (this can and does occasionally occur for the non-HP48 SX
  cards), then the calculator will start to drive the memory address
  lines and the card will still have these clamped to ground (that's
  what it does to protect itself when there is not sufficient system
  voltage to run).  This unfortunate situation may simply trash your
  memory, or if the calculator tries to drive enough of the lines high
  at the same time, several hundred milliamps may flow...for awhile that
  is, until something gives up...  On the other hand, your calculator
  and a particular non-HP48 SX card may work just fine if those voltages
  happen to be at the other end of their ranges.  These voltages are
  also slightly temperature sensitive.  It may work in the classroom or
  office and not at the beach, or vice versa.  The voltage trip point of
  the HP48 SX cards has been set lower (a different voltage control
  chip) so that this cannot occur, regardless of part and temperature
  variations.

  One other item was brought to my attention yesterday by Preston Brown
  that I should have included in my original posting here.  While most
  of us recognize that comparing RAM cards to a handful of dynamic RAM
  chips to plug into your PC is apples and oranges, it may be more
  interesting to compare the HP48 SX cards with cards for other
  products, like the Atari Portfolio, the Poquet, the NEC Ultralite,
  etc.  I believe you will find that the prices on the HP48 SX cards are
  not at all out of line.

  Steve "I claim all disclaimers..."


  From prestonb@hpcvra.cv.hp.com Fri Mar  1 17:00:00 1991
  From: prestonb@hpcvra.cv.hp.com (Preston Brown)
  Date: Thu, 17 May 1990 17:26:53 GMT
  Subject: Re: Memory Card: Give Us True Facts!
  Organization: Hewlett-Packard Co., Corvallis, OR, USA


  When the RAM cards detect that voltage is to low to operate they clamp
  the address lines to ground.  This clamping is done by turning on the
  output drivers of a custom chip included on the card.  The clamping
  current is specified to be 2mA min at the Vol output level.  Since the
  48 can be trying to drive the line all the way high even more current
  is typical.  10mA per fight is not uncommon with totals of several
  hundred mAs.

  The VDD power supply is regulated at 4.1 - 4.9 with typical parts at
  the low end (4.3).  The power to the cards is switched through a
  transistor, creating up to a 0.1V drop.  Standard Epson cards have a
  significant chance of seeing this voltage as to low and shutting down.
  We have seen cards do this in the lab.  When it occurs the calculator
  locks up with VDD pulled down to about 2.5V and 250mA being drawn from
  the batteries.  This current drain greatly exceeds the ratings for the
  power supply and can damage your calc.  The least that will happen is
  a loss of memory.

  Now, why didn't we regulate VDD higher?  The 48 has two power supplies
  VDD at 4.3 and VH at 8.5.  VH cannot be regulated higher without
  exceeding the spec for our CMOS IC process.  VH is used as the +
  voltage for the I/O.  In order to meet a +3V output level VH must be
  more then 3.6V above VDD.  (VDD is used as I/O ground).  Our power
  supply system increase the battery life and reduces the cost greatly
  for the wired I/O.

  Preston


  12.5.  Where can one obtain third party RAM cards?

  If you decide you want to look into the non-mainstream alternatives
  for RAM cards, you might like to check the following URLs:


  o  <http://www.cynox.de/>

  o  <http://stolte-edv.com/de/>

  o  <http://www.cyberline.de/kkgbr/>

  o  <http://www.Digitalis.de/>

  o  <http://home.t-online.de/home/FFFFF/>

  o  <http://www.geocities.com/Eureka/Enterprises/3190/>



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