Fetch Execute Cycle

The fetch execute cycle is a computer’s basic operation or instruction cycle. The computer retrieves a programming instruction from memory during the stages of the fetch execute cycle. It then begins to perform and execute the necessary actions for that instruction. While the computer is powered on, the CPU repeats the cycle of fetching, decoding, and executing an instruction. The stages of the fetch execution cycle were first introduced by John von Neumann. He is well-known for developing the Von Neumann architecture, which is still used by most modern computers. Any fetch execute cycle example can give you a clear understanding of the topic. 

What is the Fetch Execute Cycle? 

The fetch execute cycle is a computer’s most basic operation. The instruction set is a specialised collection of instructions or tasks that the CPU is designed to perform. It retrieves and executes instructions from the main memory. This is repeated from the time the computer is turned on to the time it is turned off.

The CPU, often known as the processor, is the computer’s brain. It is in charge of carrying out a program, which is a set of instructions. A program accepts data, processes it, and returns results. By using the stages of the fetch execute cycle, the CPU’s principal responsibility is to execute programs. The instruction cycle is another name for this. The cycle begins when the computer is switched on and ends when it is turned off. 

Stages of the Fetch Execute Cycle

Let’s look at the fetch execute cycle, which shows how the CPU can conduct calculations. The stages of the fetch execute cycle are broken into three parts: 

• Fetch

• Decode

• Execute

Fetch

It is one of the main stages of the Fetch Execute Cycle. The CPU loads the instructions into the registers from the main memory one by one. The program counter is stored in one register (pc). The memory address of the next instruction to be fetched from the main memory is stored in the computer. The data acquired during the fetch step is copied into the instruction register because it is an instruction (IR). The system is at the end of the fetch stage of the cycle now that the first instruction has been fetched.

Decode

It is one of the important stages of the fetch execute cycle, which is necessary to deduce the instruction. It is sent to the control unit through the data bus, separated into two halves. The first part is the operation code or opcode. This is the command that will be executed by the computer. The operand is the second component. Depending on the operation, data will be read from or written to this address in RAM. 

Execute

Memory is required for data processing after the decoding has been completed. When the first instruction reaches the CPU, an order to print is sent.

Processor

A processor is a sort of integrated electrical circuit that performs the calculations necessary for a computer’s function. A processor executes arithmetic, logic, input/output (I/O), and other basic commands sent by an operating system (OS). In the fetch execute cycle, the majority of other processes rely on the actions of a processor.

Microprocessor, processor, and central processing unit (CPU) are all terms that are frequently used interchangeably. Most people currently use the terms “processor” and “CPU” indiscriminately. However, this is technically incorrect because the CPU is only one of the processors of a computer (PC). Another is the graphic unit processor or GPU. It is a single-chip processor used for carrying out 3-D functions. 

Memory

Memory is similar to the human brain. It’s where you keep your data and instructions. The storage space in a computer where data to be processed and instructions to be followed are stored is referred to as computer memory. It plays an essential role in the stages of the fetch execute cycle. 

Memory is primarily of three types −

•Cache Memory

•Primary Memory/Main Memory

•Secondary Memory

Cache Memory

Cache memory is a type of high-speed memory that facilitates the CPU to run faster. It lies between the CPU and the main memory and thus acts as a buffer. 

Primary Memory (Main Memory)

The data and instructions on which the computer is currently performing are stored in primary memory. It has a limited capacity; thus, the data is lost when the power is cut. The majority of it is made up of semiconductor devices.

Secondary Memory

Secondary memory is also known as non-volatile memory or external memory. It functions slower than the main memory and is used to store data and information for an indefinite period. 

Input and Output Elements

A computer has some fundamental components. Hardware, software, programs, data, and connectivity are all included. Without these components, no computer can function. Apart from them, components of a computer system are defined as the core pieces that allow electronic equipment to operate smoothly and quickly. The following are the three basic components that help in the proper functioning of the stages of the fetch execute cycle:

•Input Unit

•Output Unit

•CPU(Central processing unit)

Input Unit

This section of the computer houses the devices the user uses to feed data to the computer. It establishes a communication channel between the user and the computer.

Central Processing Unit (CPU)

The Central Processing Unit, or CPU, is also referred to as the computer’s brain. The CPU carries out all forms of data processing functions. It saves data/intermediate results/instructions (software) and manages the computer’s overall operation.

Output Unit

This section of the computer houses the gadgets that allow the user to receive information from the computer. The output devices convert the computer’s output into a format that consumers can understand. It helps the stages of the fetch execute cycle to function smoothly. As a result, output units generate data structured by the computer based on the consumers’ preferences.

Conclusion 

The fetch execute cycle is carried out sequentially in simple CPUs, with each instruction being handled before the next one is started. It is done in parallel by current CPUs via an instruction pipeline, which means that the next command is executed before the previous command is completed. Because the cycle has been divided into individual parts, this is achievable. 

After this step, the processor goes back to the program counter to look for the next command. This cycle continues till the program terminates. The Execute Cycle is the only phase relevant to the end-user; everything else is required to make the Execute Cycle work, as it is the command’s function. If the command requires arithmetic or logical operations, the ALU is used.