Super Simple Virtual Machine And Assembler

VM Specifications

• 8 Bit Memory Space and Register Size
• 3 General Purpose Registers: R0, R1, R2
• One PC (Program Control) Register
• 16 Address Jump/Read Limitation

Instruction Set

• READ y: Load value at memory offset y (from current Program Control) into r0.
• LOAD x, y: Load value at memory address stored in register y into register x (Indirect)
• STORE x, y: Write value in register y into memory address stored in register x (Indirect)
• COPY x, y: Copy value in register y to register x
• ADD x, y: Add value in register y to value in register x and store result in register x
• JG x: Add offset of x to PC if previous instruction result was greater than 0
• SYS x: Executes system call with id x. By convention R0 is used as an argument.
  • HALT: Stops the program
  • PUTC: Output character value stored at r0 to stdout.
  • GETC: Read one character from stdin and store in r0.

Assembler Features

• Single file only.
• Labels to reference memory locations.
• In-line data prefixed with '.'.
• Ability to reference other data locations by creating a named datum with value of address of other datum.