Comma

comma (always lowercase) is an assembly language for a 4-bit fantasy chip known as the COMM4.

Registers and RAM

comma has access to 256 bytes of RAM, though this does not limit program size as the program is stored in ROM; this means it cannot be changed. Although opcodes are 4 bits wide, the registers A, X, and Y, are 8 bits wide and so are their arguments. When compiling (example: add a, 03), A becomes 0h, X is 1h, and Y is 2h. Hence, the example instruction compiles to 1003h. An address in RAM must be preceded with $, for example, sub x, $2A. All values are in hexadecimal, regardless of if in the form of A8, A8h, 0xA8, or A8_16. Separate from RAM is a 32-byte stack of 8-bit entries. All instructions are encoded into 2 bytes.

Instructions

comma Instruction Set (cIS)

Opcode	Mnemonic	Arguments
0h	nop	n/a (byte of padding as extra 0h)
1h	add	reg, int
2h	sub	reg, int
3h	cmp	reg, int
4h	jcc	label (compiles to 8-bit label, before label is 4-bit padding)
5h	pus	reg (byte of padding)
6h	pop	reg (byte of padding)
7h	int	int (4-bit) (byte of padding)
8h	xor	reg, int/reg (if reg, when compiled, pad with extra 0)
9h	and	reg, int/reg (if reg, when compiled, pad with extra 0)
Ah	nor	reg, int/reg (if reg, when compiled, pad with extra 0)
Bh	shl	reg, int
Ch	shr	reg, int
Dh	mov	reg, int
Eh	cll	label (compiles to 8-bit label, before is nibble of 0)
Fh	ret	n/a (byte of padding)

jcc variants

Opcode	Mnemonic	Form
0h	jmp	unconditional
1h	jie	if equal
2h	jne	if not equal
3h	jia	if above
4h	jib	if below
5h	jiz	if zero
6h	jnz	if not zero
7h to Fh	UNDEFINED	program halts

interrupts

Opcode	Type
0h	print (x should hold the value to be printed)
1h	halt
2h	write to disk (x should hold address and y should hold value)
3h	read from disk (x should hold address, value written into y)
4h	input (y holds value)
5h to Fh	UNDEFINED

Examples

Hello World (minus the world):

mov x, 48h
int     0h
mov x, 65h
int     0h
mov x, 6Ch
int     0h
int     0h
mov x, 6Fh
int     0h
int     1h

which compiles to:

D1 48 70 00 D1 65 70 00 D1 6C 70 00 70 00 D1 6F 70 00 71 00

This can be golfed to:

=x48,0=x65,0=x6C,0,0=x6F,0,1

GolfCOMMA

GolfCOMMA

Mnemonic	Character
nop	.
add	+
sub	-
cmp	?
jcc	see next table
pus	:
pop	;
int	,
xor	X
and	A
nor	N
shl	<
shr	>
mov	=
cll	(
ret	}

jcc variants

Mnemonic	Form
jmp	#
jie	_
jne	!
jia	^
jib	%
jiz	[
jnz	]