Applesoft: Internal program storage format



Applesoft programs are stored one line at a time starting at memory location

$801 and ascending in order by line number.  Each line is stored in this

format:



                           $8xx

 00  01  02  03  04  05  06  07  08  09  0A  0B  0C  0D  0E



 00  0D  08  0A  00  97  3A  BA  22  48  49  22  00  00  00

  E   LINK   LINE #   H   :   P   "   H   I   "   E   LINK

  O                   O       R                   O

  L                   M       I                   L

                      E       N

                              T



The first two bytes are pointers to the absolute address of the beginning of

the next line.  The first byte is the least significant.



The next two bytes are integers representing the line number of that line.

Again, the first byte is the least significant.



The next byte, a token, stands for the first Applesoft keyword.  When the

lines starts with "A = 1", the variable name (in ASCII) is first.  The

remaining command consists of keywords and symbols reduced to one byte tokens

and unmodified ASCII text.



A list of Applesoft's tokens appears on page 121 of the Applesoft Reference

manual.



The subsequent bytes are either "$00"s signifying the end of this line, or

"$3A"s, indicating multi-statement lines, followed by a "$00.



If the link field for a line is 00 00, then Applesoft considers it the last

line in the program  while running or listing.  The SAVE command uses a

different pointer for the end of the program.  $AF,B0 normally points to the

high byte in the line number of the line beyond the last line.





Apple Tech Notes





Keywords:  <None>



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This information is from the Apple Technical Information Library.



ArticleID: TECHINFO-0000057



19960724 15:55:27.00

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