NoRAL

No-Register Assembly Language - A simple assembly-style language based on a hypothetical processor that has no internal registers. Created by User:DMC

General Concept

• All volatile memory is external to the processor
• Addresses are 16 bit, stored big endian
• Memory is 8 bits
• Instructions use 0, 1, or 2 memory references
• m1 - first memory reference
• m2 - second memory reference
• xxx m1 m2 - 3 letter mnemonic, arguments separated with spaces
• Program listings are in hex
• It’s okay to write self-modifying code (maybe even necessary)
• # comment with ‘#’ as first character in a line
• Turing complete: No, only 64k addressable memory

Addressing modes

• Implied: (brk, nop, ret)
• Absolute: 2 byte address
• Immediate: 1 byte (sto)
• Indirect: mvi

The Virtual machine

Description	Memory
Total memory	0000 - ffff
Program counter	0000 - 0001 (initialized to 0200)
carry flag	0002
zero flag	0003
Top of stack	0004
Stack	0005 - 00ff
Display memory	0100 - 01ff, 32 x 8, 256 bytes
Start of program memory	0200

The Instruction set

Instruction	Op Code	Description	Flags
add	01	m1 = m1 + m2 + carry	CZ
and	02	m1 = m1 & m2	Z
jmp	03	pc = m1	–
jpc	04	if C = 1: PC = m1	–
jpz	05	if Z = 1: PC = m1	–
jsr	06	push PC, PC = m1	–
mov	07	m1 = m2	Z
nop	08	place holder	–
not	09	m1 = not(m1)	Z
orr	0a	m1 = m1 or m2	Z
pop	0b	pop m1	Z
psh	0c	psh m1	–
ret	0d	pop PC	–
shl	0e	shl m1	CZ
shr	0f	shr m1	CZ
sto	10	m1 = m2(immediate byte)	Z
sub	11	m1 = m1 - m2 - carry	CZ
inc	12	m1 += 1	CZ
dec	13	m1 -= 1	CZ
mvi	14	m1(absolute) = m2(indirect)	Z
get	15	input decimal number mod 256	Z
dsp	16	display program state during execution	–
brk	00	Halt program	–

The command DAT is also a thing but it just stores a byte directly into memory (like .byte in other assembly languages).

If you want, you can also write "mem" followed by an address. This will mean that all the following instructions will be stored at that address and onwards until the next "mem" command. At the beginning of the file, it is like the first line is "mem 0200" even though you don't need to type that.
Both are optional for an implementation to implement but I would say they are pretty easy to do.
TheCoderPro (talk) 23:55, 2 August 2020 (UTC)

Example programs

Hello World!\n

# just store all the ascii values in screen memory
sto 0100 48
sto 0101 65
sto 0102 6c
sto 0103 6c
sto 0104 6f
sto 0105 2c
sto 0106 20
sto 0107 57
sto 0108 6f
sto 0109 72
sto 010a 6c
sto 010b 64
sto 010c 21
brk
# brk only necessary if the next memory location is not zero

Output:

Program Counter:  0234
Zero Flag:          00
Carry Flag:         00
Stack Pointer:      00

+---------Screen Display---------+
|Hello, World!                   |
|                                |
|                                |
|                                |
|                                |
|                                |
|                                |
|                                |
+--------------------------------+

Clear screen

sto 1000 20
mov 0100 1000
inc 0206
jpz 0212
jmp 0204
brk

Output:
Program Counter:  0213
Zero Flag:          01
Carry Flag:         01
Stack Pointer:      00

Truth Machine

get 0100
jpz 0211
sto 0100 31
inc 0208
dsp
jmp 0206
sto 0100 30
dsp
brk

External resources

• NoRAL – Interpreter in Python 3
• Javascript / PHP Interpreter