Four stages(cycles) of a computer:

You are looking at your computer right now. Whether you are using the operating system Apple, Linux or Windows. But do you know the four stages(cycles) that makes your computer work?

What is a computer?

A computer is a electronic machine that takes a instruction and then executes it.
Think: Just as your boss would give you a instruction.
For example: He would ask you to file some paperwork.
Then you would execute that instruction by filing it in the filing cabinets.

What are the four cycles?

A computer accepts 1.)input 2.)processing 3.)Storage and 4.)Output

Analogy:

You need to wash your clothes so you use a washer and dryer.

1. 1. Input(step # 1): You put your clothes and then the dish water soap in the washing machine. That is input. Input is entering data into a computer from the outside world. But in this instance you are entering(putting) clothes into the washing machine.
   2. Processing(step # 2):
      Processing is the process in which the clothes are washing and the spinning that is happening to wash the clothes. Processing is the computer thinking. The computer does something with the data that is entered in the input stage. But in this instance the clothes are being processed in the washing machine.
   3. Storage(step # 3):
      You should notice that your clothes are now washed in the washing machine. That is storage. Storage is information(data) that is stored. But in this instance your clothes are now being stored in the washing machine ready to take out.
   4. Output(step # 4):
      The clothes should now be clean and washed. That is output. Output is the information(data) now presented in a readable format. For example: it gets displayed on a screen. Which is an output device.

Now that you know the basic rundown of input, processing, storage and output lets dive more into them.

More about input

Comparing input from a computer today to the ENIAC

Lets compare the ENIAC to a computer today to get a sense of input in computers.



Imagine a computer that is not as portable and small today.
Instead imagine a monstrous computer that weighed over 30 metric tons and was around 680 square feet. Which also contained 17.468 vacuum tubes, 70,000 resistors, and 10,000 capacitors. You can imagine it as taking manpower to operate it.

That is the computer ENIAC(Electronic Numerical Integrator And Computer). The first general computer that was invented in 1945. It was equivalent of a adding machine and storage unit.

It used twenty accumulators. For each accumulator it stored a 10-digit decimal number. Which you know from this post is not applicable today.
Learn what accumulators are from this site.

But now you have input devices that are easy to enter data into the computer.

How input works

1. It reads the data(instructions) entered from the outside world into the computer from a keyboard, mouse or other input device.
2. The data inputted is then converted into digital data(binary) that can be read and handled by the computer.
3. The converted digital data gets sent to the computer storage system for further processing.

Two types of input devices

There are two types of input devices Manual input devices: and Direct data entry.

1. Manual input devices is data that is entered into the computer by hand.
2. Direct data entry is data that is entered quickly and accurately by a machine/device.
   There will be another blog post on the different types of input devices that falls into these two categories.

More about Processing

As you read above Processing is the computer thinking. The CPU is designed to process the instructions on a computer.

What is a CPU(microprocessor)?

CPU is an integrated circuit that is the brain and heart of your computer.
Your computer can not beat without it. Since it contains all the circuitry that the computers handles all the instructions with.
Think: You have a heart. But what if you did not have a heart? Then you would not be able to function and not live to see another day. Same as a CPU. It is the heart of the computer. Without it the computer would not know what to do.

The three main components of the CPU

1. ALU(Arithmetic Logic Unit) is the component that performs the final processing by the CPU. When it is done processing it is sent to the computer memory.
   Its job is to do the mathematical and logical operations.
   Think: You can compare it to a calculator. The calculators job is to perform mathematical operations. Same as the ALU(Arithmetic Logic Unit)
2. Immediate access store holds all the data and instructions that are waiting to be used by the Control Unit
3. Control Unit is the traffic system in the CPU. It directs the flow of traffic of data and instructions in the computer system.
   Think: You can compare it to a traffic cop because his job is to help direct the flow of traffic.
   Same as a Control Unit. The control unit helps direct the flow of data in the computer system.

The clock

The clock is the timing device of the CPU(microprocessor).
The processor executes one thing at a time. Its the time given by a clock just like an oscillator.
Short definition of oscillator
An oscillator is a periodic fluctuation between two things based on changes in energy.
An oscillator runs 0,1,0,1,0.
Each time the clock changes the processor executes one instruction.
Rule of thumb: Faster clock rate = faster CPU

More about storage(memory)

As you read above storage is information(data) that is stored. Without storage your data would not be saved.

What are the two main types of storage?

A computer accepts Primary storage and Secondary storage as the two main types of storage.

Analogy:

You are at your local library looking for a book on one of the shelves.
You see a book you want. So you grab a book off of the shelf which is Secondary storage . The books in secondary storage that are not being used are filed away and stored on the shelves.
You decide to sit down on the libraries couch or table to read the book. You are now in Primary storage

More about Primary and Secondary storage

Main memory = Primary storage

Primary storage is designed to hold data(instructions) on a short term(temporary) basis. It connects to the computer processor for easy access.
It's also Volatile meaning that since the memory is held on a temporary basis. It gets erased when the power is turned off.

Brain scenario

Human brains are complex. They have a conscious and sub conscious.
In your conscious you are accessing information(data) in the part of conscious brain right now. While in your sub conscious mind you are accessing information(data) that happened a while ago.

Computer scenario based on conscious and sub conscious

RAM is short term memory. It holds and stores data(instruction) that currently are in use in primary storage for fast retrieval. When the computer is on RAM gets work done but when it's off it loses the data.

What happens when RAM fills up?

The processor(conscious) has to go to the hard disk(sub conscious) to to receive more memory. If you got more RAM then it would reduce the number of times the computer processor has to read the data from the hard disk which makes it more faster.

ROM(read only memory)

ROM can be read only. Hence read only in Read only memory.
Even when the computer is powered off ROM remains and can not be removed.

Auxiliary Storage = Secondary Storage

Secondary storage holds data that is currently not being processed. The data is filed away waiting to be used.
It's non-Volatile meaning that the data is still there when the power is turned off.

Hard drive Scenario

When a program runs or a file is opened, the computer copies the data from the Hard drive to RAM which gets stored in your conscious mind. When you are finished with the program the data is then copied back into the hard drive where it remains in the sub conscious mind until it needs to be accessed again.
Rule of thumb: Faster hard drive = faster computer

More about Output

As you read above Output is the information(data) that is presented in a readable format.
You are already using output devices in your daily life.
Think: of a monitor. Without the monitor there would be no data(information) outputted.

How Output works

1. It reads data(binary code) from the computer.
2. The data(binary code) is then converted into human-readable form
3. It then supplies the results of the now human-readable form to the outside world

I hope you enjoyed my introduction on the four stages(cycles) of your computer. I just covered the surface of these four subjects. There is so much more you can learn. Go out and explore more about the four stages(cycles) that make up your computer.