Processor Emulator

This is a simple emulator for a processor written in C. It simulates the execution of machine instructions stored in memory.

Table of Contents

• Introduction
• Features
• How the Processor Works
• Usage
• File Structure

Introduction

This emulator is designed to execute machine instructions stored in memory. It supports basic arithmetic, logical, and data transfer operations.

Features

• Instruction Execution: Executes machine instructions loaded into memory.
• Arithmetic and Logical Operations: Supports ADD, SUB, AND, OR, XOR operations.
• Data Transfer: Supports LOAD and STORE operations between registers and memory.
• Error Handling: Provides error messages for file operations, memory allocation, and invalid instructions.

How the Processor Works

Supported Instructions

The processor supports the following instructions:

• LOAD: Loads data from memory into registers. Example: LOAD R1, #4 or LOAD R1, LOC.
• STORE: Stores data from a register into a memory location. Example: STORE R1, LOC.
• ADD: Computes the addition of Operand2 and Operand3 and stores the result in Operand1.
• SUBTRACT: Computes the subtraction of Operand2 and Operand3 and stores the result in Operand1.
• AND: Computes the bitwise AND of Operand2 and Operand3 and stores the result in Operand1.
• OR: Computes the bitwise OR of Operand2 and Operand3 and stores the result in Operand1.
• XOR: Computes the bitwise XOR of Operand2 and Operand3 and stores the result in Operand1.

Instruction Encoding

Assembly instructions are converted into machine instructions using a specific encoding scheme:

• The first bit (T-bit) indicates the type of instruction: 1 for data transfer instructions and 0 for arithmetic or logical instructions.
• The next 4 bits represent the instruction opcode, determining the operation to perform.
• For data transfer instructions, the I-bit (Immediate bit) indicates whether Operand2 is a constant value.
• Operand1, Operand2, and Operand3 are encoded as specific bit sequences representing registers or constant values.

Operand Encoding

• Registers are represented by 3-bit sequences, ranging from R0 to R7.
• Constant values, if used, are represented in 4-bit 2’s complement system.
• For Load and Store instructions, Operand3 is always null (000), and Operand2 is always a memory address.

Program Data

The program's data is stored in data.txt, with each line containing a memory address and the data to be stored at that location. The format of the input files (program.txt and data.txt) can be understood by referring to the provided sample files.

This system provides a flexible and structured approach to executing machine instructions and handling data within the processor emulator.

Usage

1. Clone Repository: Clone this repository to your local machine.
2. Compile Program: Use a C compiler to compile the processor_emulator.c file.

   gcc processor_emulator.c -o processor_emulator

3. Run Program: Execute the compiled program.

   ./processor_emulator

4. Input Files: Ensure the input files (program.txt and data.txt) are present in the same directory as the compiled program.

File Structure

• processor_emulator.c: Main C source code file containing the processor emulator implementation.
• program.txt: Text file containing machine instructions.
• data.txt: Text file containing data to be loaded into memory.