Program Counter and Instruction Address Quiz

Central Processing Unit (CPU) Overview

• The program counter (PC) represents the address of the next instruction to be executed within the CPU.
• RAM stands for Random Access Memory, which is a type of volatile memory used by the CPU to store data and instructions temporarily.
• The Arithmetic Logic Unit (ALU) is the component responsible for performing arithmetic and logical operations within the CPU.

Memory Types

• Non-volatile memory retains data even when the computer is powered off, ensuring information is not lost.
• The Memory Address Register (MAR) stores the memory address of the next instruction to be executed.

Program Counter Specifics

• In the IBM PC architecture, the program counter is referred to as the Instruction Pointer (IP).
• CPU registers include places like the accumulator, but memory buffers are typically not classified as CPU registers.

Program Counter Functionality

• The program counter’s primary function is to keep track of instruction sequences and ensure proper program execution.
• The control unit within the CPU is responsible for executing instructions stored in memory.

Program Counter Initialization

• At the start of execution, the program counter must be initialized to the memory address of the first instruction.
• The program counter is incremented by the CPU after each instruction execution, facilitating the correct sequence flow.

Example of Instruction Execution

• If a CPU’s program counter currently has a value of 07FFH, incrementing it will change the address to 0800H, pointing to the next instruction.

Test your knowledge on the relationship between the program counter and the address of the next instruction. Identify the address of the next instruction when the program counter becomes 1404.