 18 Trevelyan Road
 London SW17 9LN
 
 Tel:  01-767 4254 most afternoons and evenings
 
 3rd September 1987
 
 
 Dear Porter,
 
 I hope DE is now completely stabilised. The final version, version 3,
 of the porting instructions is enclosed. Changes from and additions to
 version 2 are summarised below.
 
 CHANGES TO EXISTING INSTRUCTIONS
 
 GET            Line editing control codes introduced
 PUT            Backspace is no longer destructive
 MCALL          Changed to allow a table of arguments to be passed,
                and an error condition to be returned
 JU/JF/JT/JD    Relative jump offset meanings changed
 
 OTHER CHANGES
 
 *  The boundary between DATA and ROM logical address spaces has been
    changed from 1000H to 0800H (This was necessary because I-APL went
    over 28K towards the end of development).
 
 *  The message table has been extensively changed.
 
 *  Line editing is now part of I-APL; there is _no_need_ to write a
    line editor.
 
 *  The "missing" alphabet is now nominally the underscored lower-case 
    alphabet.
 
 NEW INSTRUCTIONS
 
 Many new instructions have been added to reduce the object size; with
 these instructions, a reduction from over 29K to just above 25K has
 been achieved. The DADD instruction is an unpacked BCD addition
 instruction, which speeded up floating point operations in I-APL by a
 factor of 4 when it was introduced. The CASE instruction is an indexed
 indirect call instruction. Several skip instructions (single byte very
 short jumps) have been introduced. Most other instructions are
 combinations of previously defined instructions.
 
 PROGRESS TO DATE
 
 I-APL is finished. This means that we are now waiting for you to
 complete your brave efforts as soon as possible, so that we can have
 versions for testing, and releasing to the wide world in the near
 future.
 
 Tony Cheal has impressed us all by producing THREE complete DEGO's
 already--for the BBC Micro, the Sinclair QL, and the Archimedes
 (Acorn's 32-bit RISC machine). His BBC implementation rivals an IBM PC
 for speed, and the Archimedes version runs 6 times faster than that.
 Because of the importance of the BBC version, we have given him extra
 support which the rest of you haven't received, but even so he updated
 his DEGO from version 2 to version 3 with only the object file of my PC
 version to work from (ie no source or documentation). We hope some of
 you might be inspired by this to write 4 or 5 DEGO's, but we will
 settle happily for just one each.
 
 TESTPORT
 
 Enclosed is the source and DE object of a short DE program called
 TESTPORT. This executes and checks many of the DE primitives, and
 should be of use to you when you are debugging your DEGO.
 
 Here is a sample output from a run of TESTPORT:
 
 C>dego testport.deb
 ABCDEFGHIJKLMNOPQRSTUVWXY
 ABCDEFGHIJKLMNOPQRSTUVWXY
 Ok
 
 Type a line
 qwertyuiop                      [line typed, followed by ENTER]
 Ok
 Hit ESCAPE key                  [ESC pressed]
 Ok
 
 First three messages:
 WHAT
 :SYNTAX
 INCORRECT COMMAND
 
 WS size = 30000 = #7EED
 
 Do you want a print test?       [y typed]
 Ok
 
 Do you want a file test?        [y typed]
 Write ok
 Read ok
 Find ok
 Erase ok
 Ok
 
 C>
 
 WHAT WE WANT FROM YOU
 
 Appendix A of the I-APL instruction manual documents the use of I-APL
 on each machine for which it is available. We are asking you to write
 appendix A for the computer to which you are porting.
 
 Enclosed with this porting kit are the manual and the source code and
 documentation disks. Please follow the format of Appendix A in the
 manual when writing your own. If you can provide the document on a 360K
 IBM PC floppy disk, we would appreciate it. In any case, please send a
 printed copy of the documentation when the port is completed. If you
 can't print APL characters, just write them in by hand.
 
 ENCLOSURES
 
 *   Manual
 *   Version 3 of the porting instructions
 *   Tony Cheal's notes on 6502 and 68000 implementation
 *   C and assembler source code for I-APL, including character sets
 *   DE source code and DE object dump of the TESTPORT program.
 
 Yours,
 
 Paul Chapman, I-APL implementor, co-ordinator for porters
 
 
