Little man computer (LMC) is a simple model of a computer that is generally used for learning purposes. When I first read about LMC I tought that programming my own simulator would be a great learning opportunity. Simulator is mostly based on Wikipedia entry of LMC. My simulator also has a functional assembler that supports mneumonics and labels for ease of programming.

1. Open the app
2. Choose a pre-loaded program
3. Click Load to get the program
4. Click Assemble to assemble the program to the memory
5. Click Step/Run to run the program

The computer has five registers. Three of them hold an integer value and two of them have a boolean value. Program counter holds the value for the next instruction to be executed. Accumulator is used as a work memory that is used in almost every instruction. Cycle count counts the cycles your program has used and can't be altered or accessed. Negative flag shows if accumulator value is negative after a subtraction operation. End of program flag is used to indicate that the end of the program has been reached.

Memory consists of 100 slots of 3 digit decimal numbers. The same memory is used for both instructions and program memory.

Instructions consist of 3 digit decimal numbers where first digit generally stands for instruction to execute and last two digits stand for memory address that are used with instruction.

1. Menubar

• About
  • Links to the github page.
• Load
  • Loads a template program to the code input.
• Assemble
  • Assembles code to the memory.
• Step
  • Execute the next instruction.
• Run
  • Executes the program instantly until the end (or 1000 cycles).

2. Code Input

• Input your code here.

3. Reg

• PC
  • Shows the current value of the program counter.
• CC
  • Shows the amount of computer cycles executed so far.
• AC
  • Shows the current value of the accumulator.

4. Inbox

• Here you can enter the input. Each value is separated by new line.

5. Outbox

• Your program prints the output here.

6. Memory

• Shows current value in each memory address.