Learn about the main functions of a computer.

How Computers Work

From clicking our mouse to turning up the volume of the speakers during our favorite song, we are constantly giving our computers input. We can think of input as how we as people physically interact with computers. We give our computer commands by interacting with various physical sensors (like buttons) which then get turned into data for our computer to process.

So how does a simple act such as clicking a mouse become the catalyst for a computer to carry out an action? First, we need to establish a connection from our input device to our computer through a physical port, which is usually attached to the computer's motherboard. 

The input device's job is to detect and report any type of event; for example, a mouse can sense the action of being clicked. Once an event is received by the input device, it reacts by sending information to the CPU. In order to properly "speak" with the CPU, information needs to be communicated using binary code which are instructions composed of `0`s and `1`s. 

Once the input is converted into binary, it is sent to the CPU to be processed.


Numbers on a keyboard are being pressed. The dial on a speaker is being moved around. A mouse is being clicked. As these interactions happen, data is sent to the computer.

Input

Great job reaching the end of this lesson. Let's go over what we learned about how a computer works:
* Input is data we give to our computers
* Processing is comprised of the translation of input and the instructions given for output
* Memory is used to store either temporary or permanent information
* Output is the information that gets returned by the computer
 
Now that we have a basic overview of how a computer works, we're ready to take a deeper dive into learning about the processes behind making a computer functional. 



A person interacting with their computer by listening to music and typing.

Review

Computers make up the world around us - from robots to phones to our coffee machines, modern appliances are often powered by computers. We rely on this technology on a daily basis; therefore, we should ask ourselves the following question:

**How does a computer work?**

Using a computer is an interactive experience. When we press a button on our keyboard to type something, our computers know what characters to display. When we move our mouse, computers generate a cursor that mimics the mouse's movements. How does a computer know what to produce based on the interactions we have with it?

In this lesson, we'll go over the four main functions of a computer that make these interactions possible:
* Input
* Processing
* Memory
* Output

Let's get started!


A person interacting with their computer by typing and listening to music.

Introduction

Once we have some data, we need to process it so that our computer can figure out what we're asking it to do and how to execute those requests. The job of processing information is given to the central processing unit, or CPU.

The CPU controls all the different components between hardware and software. We can think of it as the "brain" of the computer! The CPU also holds the responsibility of establishing communication between hardware and software. 
For example, if we turn the dial on our speakers up, data about that interaction is sent to the CPU. The CPU then deciphers the information and sends instructions to the speaker about how to handle this task. If we want to run software on our computer, it is also up to the CPU to perform all the necessary operations.

That's a lot of responsibility for one piece of hardware. With all the different software and processes available to us, how can the CPU take in information and execute the associated instructions so quickly? This is where computer memory comes in handy!  


Processing

Our computers have a lot of information to process - where does all this data get stored? Computer memory refers to the system or device used to store computer-based data temporarily or permanently. The type of hardware we use to store data depends a lot on how long we need to hold on to that information.

#### Primary Memory

Not all memory needs to last forever. Sometimes we just need information temporarily. For example, if we want to order food, we only need to remember the restaurant's phone number long enough for us to dial the number - then we can forget that information until the next time we order food.

This same idea applies to running software on our computers. When a command to run a program is sent to the CPU, the CPU retrieves data from Random Access Memory, or RAM, in order to access what instructions it needs to execute. Accessing data from RAM is significantly faster than accessing data from other memory systems. 

This type of data is also only stored temporarily; once we exit a program or turn off the computer, the data is lost. For example, if we exit a word-processing application before saving, anything we wrote in the document is gone.

#### Secondary Memory

If we upload 150 photos to our computer, the computer needs a space to permanently store the data associated with the images so that we could access the pictures anytime. This type of data would most likely be saved onto our computer's hard drive.

Data travels between the CPU and primary memory frequently and quickly. Data travels between the CU and secondary memory slowly and infrequently.

Memory

Once the CPU processes data and sends out instructions on how to handle it, output is produced! We can think of output as the computer fulfilling the command we gave it through an output device. 

Examples of output devices include the following:
* Monitors
* Speakers
* Printers

For example, if we clicked a mouse to open a file, the output would be the monitor displaying the file's content. If we turned the volume on our speakers up, the output would be the sound becoming louder. 

Output is the final step in the process of our computer interaction.

A desk is supporting a computer monitor and speakers. The speakers are playing music. The monitors show a video of planets moving. A printer is printing images. All of these examples show output. 