Opcodes used by THE VASSAR INTERPRETER

Addressing modes
	_n	- an offset from the beginning of memory (global) NEW
	%n	- an offset into the current stack frame
	@%n	- absolute memory address of offset into stack frame
	@%0	- offset of the start of the stack frame
	^_n	- see below
	^%n	- dereference the memory address as a pointer

There is no @_n since @_n = _n = n.

Source operands can be literals, or a memory addressing mode.
Destination operands are always a memory addressing mode.


Opcodes  (CASE SENSITIVE)

add	op1, op2, op3
sub	op1, op2, op3
div	op1, op2, op3	
mul	op1, op2, op3	
	computes op1 + op2, op1 - op2, etc
	result is stored in op3 which must be an address (or alias)

fadd, fsub, fdiv, fmul  
	floating point version of the above

uminus  op1,op2
        negates the value of op1 and stores the result in op2

ltof	op1, op2
	converts op1 from integer to floating point representation
	stores the result in op2

ftol	op1, op2
	converts op1 from floating point to integer representation
	stores the result in op2

move	op1, op2
	op1 contains a value
	op2 contains the memory offset of the destination

stor	op1, op2, op3
	saves op1 in op3[op2] (array style access)
	op1 contains a value
	op3 contains the memory offset of the destination
	op2 contains the offset from op3	

load	op1, op2, op3
	loads op1[op2] into op3  (array style access)
	op1 contains the memory offset of the source
	op2 contains an offset from op1
	op3 contains the memory offset of the destination

goto	op1
	op1 contains a number, execution will jump to the 
	    instruction labeled with op1.

blt	op1, op2, op3
	if ip1 < op2 goto op3
	op1, op2 contain values
	op3 contains a label

ble	op1, op2, op3
	if ip1 <= op2 goto op3
	op1, op2 contain values
	op3 contains a label

bgt	op1, op2, op3
	if ip1 > op2 goto op3
	op1, op2 contain values
	op3 contains a label

bge	op1, op2, op3
	if ip1 >= op2 goto op3
	op1, op2 contain values
	op3 contains a label

beq	op1, op2, op3
	if ip1 = op2 goto op3
	op1, op2 contain values
	op3 contains a label

bne	op1, op2, op3
	if ip1 <> op2 goto op3
	op1, op2 contain values
	op3 contains a label

ceq	op1, op2, op3
cne	op1, op2, op3
clt	op1, op2, op3
cgt	op1, op2, op3
cle	op1, op2, op3
cge	op1, op2, op3
	similar to the above branching instructions but stores
	one in op3 if the comparison is true, zero otherwise

print	op1
	prints op1 as a string
	op1 is a literal string or a STR variable

outp	op1
	op1 is a memory offset, outputs the number stored
	at that offset.

inp	op1
	causes an input action, a value (number) will
	be read from stdin and stored to op1

foutp, finp
       floating point versions of the above

newl   outputs a carriage return

param	op1
	pushes op1 onto the parameter stack
	used to prepare for a function call

call	name, count
	name is the function name
	count contains the number or parameters push on the 
	stack with param

nop
	does nothing

exit
	terminates execution of the program

alloc	 n
	adds 'n' storage locations to the current stack frame

free n
	releases 'n' storage locations from the current stack frame

PROCBEGIN name
	marks the begining of a function declaration

PROCEND
	marks the end of a function

DATA
	declares the beginning of a data section

CODE
	declares the beginning of a code section

LONG	x, y=n
	declares the variable x and y, y will be 
	initialized to n at startup

STR	s="Hello world"
	declares the constant string s
	STR variables MUST BE INITIALIZED
	they ARE NOT arrays of char