wdr

The WDR Paper Computer is a simple educational computer model designed to teach the fundamentals of computer architecture and assembly language. It was introduced by Wolfang D. Rautenberg in the 1980s and it's a useful learning tool for low-level programming concepts.

More details: Paper Computer on XXIIVV wiki

wdre, aka this implementation

While the WDR Paper Computer was originally designed as a purely paper-based tool, this project brings it into the digital realm using Lua.

The goal is not to replace the original learning experience but rather to use WDR as a foundation for exploring computer architecture, assembly language, and low-level programming concept in a more interactive way.

Assembly

The WDRE assembly language is a minimalistic intruction set. Unlike the original WDR Paper Computer, which uses line numbers for jumps and data manipulation, WDRE operates with memory addresses. This expanded version introduces RAM and additional instructions for working with it.

Register 0 servers as a memory address pointer, while register 1 is used to store or retrieve data from RAM.

This implementation limits the number of registers to 4: 0, 1, 2 and 3.

Instruction Set

• INC REG - Increments the value of register REG
• DEC REG - Decrements the value of register REG
• LD0 ARG - Load the value ARG into register 0
• LDR - Loads into register 1 the value stored in memory at the address specified by register 0
• STR - Stores the value of register 1 into memory at the address specified by register 0
• ISZ REG - If register REG is 0, skip the next instruction; otherwise, execution continues normally.
• JMP ARG - Sets the program counter to ARG
• STP - Stops program execution

wasp - the assembler

wasp is the assembler used for the WDRE implementation. It converts the assembly code in machine-readable instructions that can be executed by the WDRE.

• Comments: anything starting from ; to the end of the row is considered a comment and will be ignored during the assembly process.
• Labels: you can define label using the syntax LABEL:. Labels are useful for specifying jump target

Example:

; This is a comment
START:
	LD0 10 		; Load the value 10 into register 0
	JMP START 	; Jump back to START