Python.AssemblyImageEncoder

Encodes a custom set of assembly style instructions into an image. Syntax has been inspired by the Little Man Computer (LMC) created by Stuart Madnick in 1965. An online model of this can be found at https://peterhigginson.co.uk/LMC/ and the idea of executing a program from an image from https://github.com/roo2319/Scritch. Note that this is not the best model of assembly as it has a modest instruction set and lacks a stack. The main purpose of this program is for those who find Steganography interesting to have a play around.

Download

Clone

Using The Command Line

1. Press the Clone or download button in the top right
2. Copy the URL (link)
3. Open the command line and change directory to where you wish to clone to
4. Type 'git clone' followed by URL in step 2

$ git clone https://github.com/[user-name]/[repository]

More information can be found at https://help.github.com/en/articles/cloning-a-repository

Using GitHub Desktop

1. Press the Clone or download button in the top right
2. Click open in desktop
3. Choose the path for where you want and click Clone

More information can be found at https://help.github.com/en/desktop/contributing-to-projects/cloning-a-repository-from-github-to-github-desktop

Download Zip File

1. Download this GitHub repository
2. Extract the zip archive
3. Copy/ move to the desired location

Language information

Built for

This program has been written for Python 3 and has been tested with Python version 3.7.0 https://www.python.org/downloads/release/python-370/ on a Windows 10 PC.

Other versions

To install Python, go to https://www.python.org/ and download the latest version.

How to run

1. Open the .py file in IDLE
2. Run by pressing F5 or by selecting Run> Run Module

Syntax and instructions

Some information exists in the .py file as how each instruction is used. Additionally, some example programs will be provided. See below for some more documentation.

Code files and execution

• Source code files are best saved as text files (.txt)

• Source code is assembled into 'object code', these are bitmaps (.BMP)

• The bitmaps can be read into a series of integer tokens. These are then executed

Data types

Int (8 bits)

The code is written to an image directly (through reading and writing to the image in a binary format) one byte at a time. The lowest 32 ints are reserved for instructions (16) and registers (16) - Note there are fewer instructions and registers than these. Thus the minimum int that can be used safely is -96 and the maximum int is 127.

Char (8 bits) - UNSUPPORTED

No support is currently included for chars (through input or output) but this is something that I may consider.

Instructions

General considerations:

• Instruction parameters follow the instruction and are space separated

• Instructions must output to a register (see later for more information on registers)

Instruction	Arguements	Equivalent	Example	Reserved Value
REM	N/A	// (Java) # (Python)	REM This is a comment	N/A
ADD	out arg0 arg1	out = arg0 + arg1	ADD r0 2 3 Register r0 will contain the value 5	-128
SUB	out arg0 arg1	out = arg0 - arg1	SUB r0 r1 r2 Register r0 will contain the result of r1 - r2	-127
MULT	out arg0 arg1	out = arg0 * arg1	MULT r0 2 3 Register r0 will contain the value 6	-126
DIV	out arg0 arg1	out = int(arg0 / arg1)	DIV r0 9 3 Register r0 will contain the value 3	-125
INC	reg	reg = reg + 1	INC r0 Register r0 will be incremented by 1	-124
DECR	reg	reg = reg - 1	DECR r0 Register r0 will decremented by 1	-123
MOV	reg arg0	reg = arg0	MOV r0 7 The value 7 is moved into the register r0	-122
OUT	reg	print(reg) Outputs the register	OUT r0 The value of r0 is outputted to the screen	-121
IN	reg	reg = int(input()) Accepts input and writes to the register	IN r0 User input is taken and stored in the register r0	-120
END	[none]	Terminates the program	END The program is terminated	-119
BRA	token	Behaves like a GOTO statement. Rather than jumping to a line or tag, jumps to a specific token (REM and any comments following do not count)	BRA 3 Jumps to token 3 (the fourth token in the program - tokens include opcodes and operands)	-118
BRP	token reg	Behaves like a GOTO statement (similar to above) if the register holds a positive value (1 or more)	BRA 3 r0 Jumps to token 3 if r0 > 0	-117
BRZ	token reg	Behaves like a GOTO statement (similar to above) if the register is equal to 0	BRA 3 r0 Jumps to token 3 if r0 = 0	-116

Registers

General considerations:

• Register contents are not bound, though safe ints should be used (-96 to 127)

Register	Reserved Value
r0	-112
r1	-111
r2	-110
r3	-109
r4	-108
r5	-107
r6	-106
r7	-105

Licence

MIT License Copyright (c) fredhappyface (See the LICENSE for more information.)