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<title> OS/A65 BASIC interpreter</title>
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<h2>Warning!</h2>
<strong><big>
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.<p>
Do not try to assemble it or run it!
</big></strong>
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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.
<h4>changed commands</h4>
<ul>
<li> OPEN fnr, drv, mode, name <br>
'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.
<li> LOAD name, drv
<li> SAVE name, drv <br>
'drv' has changed to the OS/A drive number
<li> LIST name, drv [,a-b]<br>
You can now list a program directly to a file. a and b are filenumbers
and optional (as usual with list)
<li> SYS adr<br>
'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.
</ul>
<h4>new commands</h4>
Some parameter can be left off, I was just to lazy to write all the brackets...
<ul>
<li> DIR [mask,] drv<br>
print directory of a drive
<li> MKDIR name, drv<br>
creates new subdirectory
<li> RMDIR name, drv<br>
remove (empty) subdirectory
<li> SCRATCH name, drv<br>
remove file
<li> RENAME name1 TO name2, drv <br>
rename a file 'name1' to 'name2'.
<li> DELETE a-b <br>
remove BASIC lines a-b; syntax is the same as with list
<li> RENUMBER start, step, a-b<br>
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.
<li>RENEW<br>
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.
<li>DUMP<br>
prints all variables
<li>FIND text<br>
list the lines where 'text' occurs.
<li>HIMEM adr<br>
sets a new end of basic ram address and executes a CLR.
<li>LOMEM adr<br>
sets a new basic program start address and executes a NEW.
<li>QUIT<br>
In contrast to the original C64 Basic interpreter this one can be left...
<li>ENTER name, drv<br>
redirects STDIN to the given file, so that e.g. a complete basic program
can be read in from an ASCII (not tokenized) file.
<li>CALL adr, a, x, y, c, ra, rx, ry, rc<br>
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.
<li>SPUT adr, string<br>
Write a string directly into memory at adr, end with nullbyte.
<li>SGET adr, len, stringvar<br>
reads len bytes from memory at adr and saves it in string variable.
</ul>
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