The Central Processing Unit (CPU) serves as the brain of a computer, executing instructions from a computer program through a fundamental process known as the fetch-decode-execute cycle, commonly referred to as the instruction cycle. This cycle comprises a series of operations that the CPU performs to carry out each machine language instruction within a program.

The first step in this cycle is the fetch operation. During this phase, the CPU retrieves the instruction from the main memory (RAM) and loads it into its internal memory, specifically the Instruction Register (IR). The Program Counter (PC) plays a crucial role in this process by tracking the memory address of the next instruction to be fetched. After the instruction is fetched, the PC is incremented to point to the subsequent instruction.

The second step is the decode operation. In this phase, the Control Unit (CU) of the CPU decodes the fetched instruction to ascertain the required operation. The operation could be arithmetic, data movement, or control-related. The CU utilizes the opcode (operation code) of the instruction to identify the type of operation that needs to be executed.

The final step is the execute operation. Here, the CPU performs the operation determined during the decode step. This could involve the Arithmetic Logic Unit (ALU) if the operation is arithmetic or logical, or it may entail transferring data between registers or between memory and a register. In cases where the instruction is a control operation, such as a jump instruction, the CPU may alter the flow of execution within the program.

This cycle repeats for each instruction in the program until the program concludes. The speed at which the CPU completes this cycle, typically measured in cycles per second (hertz), is a critical factor influencing the overall performance of the computer system. Additionally, the CPU’s capability to execute multiple instructions simultaneously, known as parallel processing, can significantly enhance performance.