Warning!

The BASIC interpreter is derived from copyrighted code! So the basic interpreter is only an educational example of how to port other programs from the C64 or other PET computers to the OS/A65 operating system.

Do not try to assemble it or run it!

---

The basic interpreter is taken from the C64. I de-assembled it into normal source code and patched it to work with OS/A65 and multitasking. Several commands are changed and others, most notably the BASIC V4 commands, are added.

changed commands

• OPEN fnr, drv, mode, name
  'drv' has changed from the commodore specific device id to the OS/A drive number. 'mode' then is the command to open a file, i.e. FS_xxx.
• LOAD name, drv
• SAVE name, drv
  'drv' has changed to the OS/A drive number
• LIST name, drv [,a-b]
  You can now list a program directly to a file. a and b are filenumbers and optional (as usual with list)
• SYS adr
  'adr' is checked for some C64 specific addresses and changes them to the routines where they are now. Detected addresses are $ff90, $ff99, $ff9c, $ffb7-$ffe7, $fff0, $fff3.

new commands

Some parameter can be left off, I was just to lazy to write all the brackets...

• DIR [mask,] drv
  print directory of a drive
• MKDIR name, drv
  creates new subdirectory
• RMDIR name, drv
  remove (empty) subdirectory
• SCRATCH name, drv
  remove file
• RENAME name1 TO name2, drv
  rename a file 'name1' to 'name2'.
• DELETE a-b
  remove BASIC lines a-b; syntax is the same as with list
• RENUMBER start, step, a-b
  change basic line numbers of the lines a-b (syntax as with list) to start, start+step, start+2*step,... All GOSUB and GOTO statements are changed appropriately in the whole program.
• RENEW
  Gets a BASIC program back that has been deleted with NEW. It only works if the program has not been overwritten by e.g. setting a new variable in memory.
• DUMP
  prints all variables
• FIND text
  list the lines where 'text' occurs.
• HIMEM adr
  sets a new end of basic ram address and executes a CLR.
• LOMEM adr
  sets a new basic program start address and executes a NEW.
• QUIT
  In contrast to the original C64 Basic interpreter this one can be left...
• ENTER name, drv
  redirects STDIN to the given file, so that e.g. a complete basic program can be read in from an ASCII (not tokenized) file.
• CALL adr, a, x, y, c, ra, rx, ry, rc
  Calls a machine language routine at adr, with a,x,y,c in accumulator, x- and y-register and in the status register. Return values are put into ra, rx, ry, rc.
• SPUT adr, string
  Write a string directly into memory at adr, end with nullbyte.
• SGET adr, len, stringvar
  reads len bytes from memory at adr and saves it in string variable.