The CPU performs four functions in every cycle decode, execute, and store

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Videos to help you understand
Excellent simulations of the machine instruction cycle
Improvements with pipelining
Introduction to Machine Cycle
What is Machine Cycle?
Steps involved in Machine Cycle
Why we Need Machine Cycle?
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This is a basic concept in computer science

The machine instruction cycle describes the order that instructions are processed in a computer.

Instructions are processed under the direction of the control unit in a step-by-step manner.

There are four fundamental steps in the instruction cycle:

1. Fetch the instruction The next instruction is fetched from the memory address that is currently stored in the Program Counter (PC), and stored in the Instruction register (IR). At the end of the fetch operation, the PC points to the next instruction that will be read at the next cycle.

2. Decode the instruction The control unit interprets the instruction. During this cycle the instruction inside the IR (instruction register) gets decoded.

3. Execute The Control Unit of CPU passes the decoded information as a sequence of control signals to the relevant function units of the CPU to perform the actions required by the instruction such as reading values from registers, passing them to the ALU to perform mathematical or logic functions on them, and writing the result back to a register. If the ALU is involved, it sends a condition signal back to the CU.

4. Store result The result generated by the operation is stored in the main memory, or sent to an output device. Based on the condition of any feedback from the ALU, Program Counter may be updated to a different address from which the next instruction will be fetched.

Data Bus: A data bus is a connection between the different parts of a computer that information is sent on.

Address Bus: The address bus is a data bus that is used to specify a physical address. A CPU will specify the memory location.[1]

Videos to help you understand

Excellent simulations of the machine instruction cycle

References

Updated: 02/07/2022 by Computer Hope

The steps performed by the computer processor for each machine language instruction received. The machine cycle is a four-process cycle that includes reading and interpreting the machine language, executing the code, and then storing that code.

Tip

The process of cycling instructions may also be known as the E-cycle (execution cycle), I-cycle (instruction cycle), fetch-decode-execute cycle, or fetch-execute cycle.

Fetch - Retrieve an instruction from memory.
Decode - Translate the retrieved instruction into computer commands.
Execute - Execute the computer commands.
Store - Send and write the results back in memory.

Below is an example of a machine cycle performing the steps mentioned above for a math problem.

The computer user enters a math problem that's stored in memory. The computer fetches that instruction from memory.
The control unit decodes that math problem into instructions the computer understands.
The ALU executes the instructions to get the answer to the math problem.
The problem's answer is sent to and stored in memory where it can be accessed and displayed to the user.

Improvements with pipelining

Early computer processors needed to wait until an instruction completed all four stages before beginning work on the next instruction. However, today's computers use pipelining, which allows the processor to begin fetching a second instruction before it has completed the machine cycle for another instruction.

ALU, Control Unit, CPU terms, Cycle, Instruction, Machine, Machine language, Program counter

____25.The CPU performs four functions in every cycle: ____, decode, execute, and store.a.bringc.transportb. exposed. fetch

Question 6(1 point)The CPU performs four functions in every cycle: ____, decode, execute, and store.Question 6 options:bringexposetransportfetch

Introduction to Machine Cycle

For the central processing unit (CPU) the machine cycle is considered a list of steps to execute the machine instruction in the computer processor. The machine cycle is considered a list of steps that are required for executing the instruction is received. The machine cycle includes four process cycle which is required for executing the machine instruction. The four process includes reading of instruction, interpretation of machine language, execution of code and storing the result. The processor performs all these four processes in repetition in a sequential manner so that instruction can be executed.

What is Machine Cycle?

Machine cycle is also known as the processor cycle. The Central processing unit (CPU) is the main component for the execution of the machine cycle as it is the main component of the computer system. The main components of the machine cycle are the central processing unit and memory unit. The machine cycle is considered a sequence of four different processes that run in a repetitive manner for the execution of an instruction. The four processes include are, a) fetch b) decode c) execute d) store. In the first process fetch, the control unit asks in main memory for the first instruction for executing which is store in the memory as some specific address which can be easily identified by a program counter (control unit). After getting the instruction the next step is to decode the incoming instruction. The CPU contains the control unit which is used for decoding the instruction in the instruction register. The register is the small component of memory that perform the operations and speed up the processing of the operation. The registers store the instruction which is fetched from the main memory of CPU. The decoding of instruction includes the breaking of the operand field in small components on the basis of instructions opcode. The opcode is part of machine language instructions which gives information about what operation needs to be performed on the instruction. After that, the instruction is executed by the computer processor. The program counter is used for tracking the instruction sequence and track the instruction address as the instruction is executed and the next instruction in the queue for the execution. As the execution of an instruction is completed the output is stored in the memory for later use so that if there is a requirement then the result can be fetched easily.

Steps involved in Machine Cycle

The four steps are briefly discussed in the below section:

1. Fetch Process

In this process, the program counter value fetched which gives the address of the instruction which needed to be executed by the CPU. The instruction is fetched from memory that needs to be executed by the processor. The computer’s main memory stores all the instruction which needs to be executed by the processor. The control unit is the component that is responsible for fetching the instruction from the memory. All instructions are stored at some address location in main memory which can be tracked using the component named as instruction counter.

2. Decode Process

In this process, the fetched instruction is decoded for the execution of an instruction. The decoding process uses the instruction register contents to decode the type of operation which needs to be applied to instruction and inform ALU (Arithmetic logic unit) so that it can be executed for the decoded operand. In the CPU architecture, the control unit takes responsibility for decoding and translating the instruction. After decoding and translating instruction the signals are sent to ALU for the execution of the decoded instruction.

3. Execute Process

In this process, the decoded instruction is finally executed by the computer processor. The CPU is responsible to execute the instruction on the input data (operand). For the computer instruction, there are majorly two components which are operation code (OP code) and operand. The Arithmetic logic unit (ALU) is the component that executes the instruction as per the OP code on the operand which is the input data. For different operation the value of OP code is different. And according to the OP code, the ALU performs the operation on instruction and then the instruction is executed by the processor.

4. Store Process

In this process, the execution result is stored in memory. Once the Arithmetic logical unit operates on data, the result of the operation and processed data is sent to the main memory for the restoration of the result. The memory (RAM) is the main component in this process as the result is stored for later use. For displaying the output on the screen the result is fetched from the main memory or can be used for some other operation as per the requirement. And the stored data is deleted after the use and the whole process is again repeated for the next instruction. All these processes are critical to the processor as the processing speed and the performance of the processor is dependent on these four processes.

Why we Need Machine Cycle?

The machine cycle is required to tell the complete flow of instruction execution so that the internal of the instruction execution can be better understand and if there is any requirement it can be further improved. The machine cycle is the sequential steps for the execution of the instruction and if it is mot there the instructions will not be able to execute properly which can give wrong results. The machine cycle is required for the execution of machine instructions by the processor.

Importance of Machine Cycle

The machine cycle is important for the execution of machine instruction by the computer processor as the device performance is based on the machine cycle. If the instruction is not performed properly the performance can be degraded by the processor. The processing speed and the performance of the device are calculated by the number of instructions that it can execute in the given time span.

Conclusion

The machine cycle has four processes i.e. fetch process, decode process, execute process and store process. All these processes are necessary for the instruction execution by the processor. By the machine cycle, the performance of the processor can be calculated and the device can be selected.