#qpybasic

This is an attempt to create a QBASIC compiler in Python, along with a VM and tools like a debugger. The compile target is a stack-machine. Most of QBASIC features are currently supported. DATA statements are not yet supported though.

You can compile a program by running:

./qpybasic.py foo.bas

This will produce a file named a.mod which can be run by:

./vm.py a.mod

The a.mod file can be disassembled by:

./asm.py a.mod

Which outputs something like this:

00100000  call      0x00100006
00100005  end
00100006  frame     0
00100009  pushi%    2
0010000c  pushi%    2
0010000f  add%
00100010  pushi%    10
00100013  add%
00100014  pushi%    1
00100017  pushi%    1
0010001a  syscall   4
0010001d  unframe   0
00100020  ret       0

You can also directly get assembly from qpybasic by passing a -d option:

./qpybasic.py -d foo.bas

An assembly level debugger is also available which can be used to step through compiled programs:

$ ./qdb.py a.mod
NEXT UP: call 0x00100006

qdb: qpybasic interactive debugger
Type help or ? to list commands.

(qdb IP=0x100000) help

Documented commands (type help <topic>):
========================================
EOF  help  mem  next  quit  reg  stack  step

(qdb IP=0x100000) step
NEXT UP: frame 0
(qdb IP=0x100006)
NEXT UP: pushi% 2
(qdb IP=0x100009)
NEXT UP: pushi% 2
(qdb IP=0x10000c)
NEXT UP: add%
(qdb IP=0x10000f)
NEXT UP: pushi% 10
(qdb IP=0x100010)
NEXT UP: add%
(qdb IP=0x100013)
NEXT UP: pushi% 1
(qdb IP=0x100014)
NEXT UP: pushi% 1
(qdb IP=0x100017)