How Does a Computer Process Information?

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Just like humans, computers use a brain to process information. For a computer, the brain is the central processing unit (CPU). The CPU is the chip that executes all of the computer's programs. It sits on the motherboard and communicates with all of the other hardware components inside the computer. Nothing can operate without going through the processor first.

The 4 Steps of Processing Information

In every computer program sits a set of instructions. The CPU uses the instructions as a guide to run the programs. To determine what to do with the instructions, the CPU goes through 4 steps to make sure the program runs without errors. The 4 steps are fetch, decode, execute and writeback.


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Fetch Phase

The first thing that needs to be done is the fetch step. When the user makes a command to open a program, the CPU receives this request and processes it. The CPU then retrieves the desired program by accessing memory for the program's location. Each program has a program counter number; this is a roadmap that the CPU uses to locate the program and get further instructions from the program.

Decode Phase

Decode is the next phase of the process. When a CPU fetches a program, it doesn't see all of the pretty graphical aspects that we see. All it sees is programming code. This code must be deciphered into a language that the CPU understands. There are literally hundreds of different programming languages that programmers use to write software programs. The CPU must first decide what language the program is written in and then decode it so that it understands the instructions that are held inside the code.


The decode process is another list of steps. The CPU breaks down the code so that it is manageable. The parts that the CPU deals with are the only ones that directly communicate with it. The opcode (indicates the numerical order of code) is used to figure out the order in which the code must be executed. There are times when a CPU can't interpret the code on its own; so it uses a translator called a microprogram. Once the microprogram has interpreted the code, it sends the instructions back to the CPU in a language that it understands.


Execute Phase

Next is the execute stage. After finding the numerical order of the instructions in the code, the CPU is now ready to execute them in order. The program is loaded and made ready for the user. Starting at Step 1, all the components necessary for the program to run efficiently is loaded using the opcode and microprogram, if necessary.


Writeback Phase

The writeback phase is the final one. During each of the previous steps, the CPU records feedback on the process. This is necessary if there was a problem during one of the steps. Even if everything loaded successful, the CPU writes the status back into memory. An example of this is when an error causes Windows to not start properly. After the computer is restarted, the CPU writes the error into memory. When the program loads again, the CPU pulls up the feedback from the last attempt and displays a message to the user. So, that is how a computer processes information; by following predefined steps and instructions inside programming code using the CPU.



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