How Computers Work


Computer Hardware Basics - Overview

Time: 1 hour

Concepts: What is a Computer? Types of computers. Computer hardware and components. How computers work. Operating Systems. Software.

This is a very short but free introduction to computers. This is intended for beginners who know very little about computers, computer hardware and how computers work.

Part 1. What is a computer?


 A computer is an electronic piece of equipment. It runs programs called software that give the computer instructions and tell it what to do. A computer can create and modify data. Computers also store data electronically for later use. Computers can be used at work to create, store and retrieve data. They can also be used for gaming. A video game console is just a computer that is designed for one specific task; to play games. Cars have computers that tell various components in your car what to do as well as monitor those components for failure. Smart phones are just small handheld mobile computers. As you can see computers come in many shapes and sizes and can perform many various tasks. 

Some examples of the different kinds of computers are:

Personal Computer: This is what most of us think of when we think of a computer. This consists of a box which holds the data and does the processing. It has an external monitor, keyboard and mouse.


Laptop Computer: The laptop is just a portable version of the personal computer. The monitor, keyboard and mouse are all built into the same box that holds the data and does the processing. It folds up and is lightweight and portable.

Server: These may look like a desktop PC in some cases, but they can also be much larger. They contain much more memory, disk space and processing power than a personal computer. Computer workstations on a network connect to servers to save and store data in a central location. Many workstation computers may connect to the server to save and retrieve data from one location where many people can access the same shared data.

Tablet: These are very small, thin lightweight computers. They usually are not as powerful as a personal computer or laptop but are extra portable. They usually do not have a keyboard or mouse. Instead they have a touch screen. 

Smart Phone: This is much like a tablet but even smaller. These devices can also be used to make phone calls, send text messages, take pictures and run small lightweight applications known as apps 

Thin Client: A thin client may look like a small PC, but these devices do very little processing on their own. These devices connect to a server on startup and all of the processing is done on the server. These are not like the other computers on the list because all of the others can do their own processing. A thin client does not even function without a server since it has very little memory, or disk space and cannot do much on its own. 


Part 2 Computer Hardware

 Computer hardware is all of the physical components that make up a computer. There is internal and external hardware. The external hardware consists of a monitor, a keyboard and a mouse. These are the components that are used to input data into the computer and tell the computer what you want it to do. The monitor displays data, programs, images, pictures, video or any other content the user requests from the computer. The keyboard is used to type commands using letters and numbers. It can also be used to input data into applications. On computers with operating systems that run a "Graphical User Interface" or (GUI), like Windows or Apple computers, you need a mouse as well as a keyboard. The mouse moves the pointer around on the screen and is used to open applications by pointing to them and clicking on an icon on the monitors screen. Some commands such as start, logon, logoff and shutdown are also made into visible elements that you can click on.

On the back of a computer there are many various inputs. Some of these are for connecting your mouse, keyboard and monitor. The power port is where your power cable connected to the power supply located inside the computer. There will also be many other ports on the back of a computer. There will probably be an Ethernet port for connecting a wire that connects the computer to the local network and the internet. There will be ports for audio devices. There will also be Universal Serial Bus or USB ports for connecting external devices such as cameras, storage devices, printers and many others types of devices.


Inside your computer....


The components inside your computer are where all of the real action happens. This is where your data is stored, where the computer processes the information given by the users input and performs the tasks it is instructed to perform. Inside your computer are many various parts connected by wires and fastened to other boards. To many people it just looks like a big complicated mess, but each component plays an important role. Here is a list of components and what they do.

Motherboard: This is the main system board that ever other device in the computer connects to. This board has many little electronic circuits that carry signals and information to and from each of the other components in the system. It also has many expansion slots for adding extra devices to your computer.

Processor: The processor or Central Processing Unit also known as a CPU is the main chip that carries out all of the tasks sent to the computer.


Heatsink: A processor gets very hot. If it gets too hot it can be damaged and the computer can crash or shut down. To carry heat away from the processor your computer case will have many cooling fans inside, but directly on top of the processor is the heatsink. This is the reason you will not be able to locate the processor on your motherboard, because it is a small chip underneath this giant heatsink. You will see this in the photos below. The heatsink is  a non moving device that has many metal fins. It draws the heat away from the processor and into the fins. A fan blows on the fins to cool them. Other fans in the computer pull heat out of the back of the computer. All of these work together to cool your processor and the internal hardare in your computer.

Hard Drive: This is where all of your operating system, software and files are all kept inside your computer. Hard drives come and many sizes. The more data you intend to store on your computer, the larger the hard drive you will need. This storage is your long term storage where files are saved.


RAM: RAM stands for Random Access Memory. This is the short term temporary memory inside your computer. It comes in small thin chips that fasten to slots in the motherboard.  

Power Supply: This is the device that gives power to all of the components inside the computer. There is a plug on the outside of the computer that connects to a power cable that you plug into a wall. On the inside this power supply has many smaller wires that connect to the motherboard and many other components 



Not all computers are put together exactly the same way, but they all have very similar parts and components. You will learn more about the parts and components in a more advanced computer hardware or CompTIA A+ course. The image to your left and the image below both show what a computer looks like with it's cover off. You can clearly see all of the components assembled together. 

Computers also have software built into the system board as well as some components called firmware. This firmware give the hardware special instructions as to how the hardware should interact with other devices or software. There is also a program called a BIOS (Basic Input/Output System that is used to adjust settings such as the system clock, hardware settings, security settings, RAM configuration, boot device order and hard drive configurations. The CMOS (Complementary Metal-Oxide-Semiconductor) is where all of the settings are stored and uses a battery to save the setting even when the power to the computer is disconnected. Without the CMOS and the CMOS battery, you would need to re-configure the BIOS every time the computer starts. These things are normally pre configured from the manufacturer and most users never have to configure these. These settings are really only to be configured by advanced users or computer service technicians.


Part 3. How do computers work?


Computers are just electronic devices. They work using electricity. The only thing electricity knows is on or off. On equals a 1 and off equals a 0. Each 1 or 0 equals a Bit. A combination of 8 1s or 0s is called a Byte. The letter A to us would equal  01000001 to a computer and the number 1 to us would look like  00000001 to a computer. This is called Binary Code. Binary code is the use of 1's and 0s to represent different characters in electronic devices. When you press a button on  keyboard this sends a signal to the system board as a series of 1's and 0's and the information is processed then translated back to your screen from 1's and 0's to a character represented by the button your pressed on the keyboard. This is why when you type the letter A you actually see a letter A show up on the screen. Your computer is constantly taking your input, reading it and then translating it back into a language that you understand. It then displays it on your screen.

Let us look at units of data and what they are named so that we have an understanding.  

 A 1 or a 0 is a bit. 

Eight 1's or 0's in any combination are called a Byte.

1024 Bytes of data is known as a KiloByte or KB. They are called KiloBytes because they are approximately 1000 Bytes.

1024 KyloBytes of data is known as a MegaByte or MB.

1024 MegaBytes of data is known as a Gigabyte or GB.

1024 Gigabytes of data is known as TeraByte or TB.

1024 TeraBytes of data is known as a PetaByte or PB. 

Hard Drives


Older computers used punch cards or magnetic tapes to store data on. The problem with these is that they could only be read serially, meaning from beginning to end. If the data you wanted was in the middle of the tape you still hard to start from the beginning and wait for the entire tape to load. This wasted a lot of time. To solve this problem, IBM invented the hard drive. 

The hard drive contains a silver disk inside of it called a platter and a motorized read write head. The disk is devided into tracks and sectors. Each sector is configured to hold a certain amount of data. How the disk is layed out and configured depends on how it was formatted. One disk can be formatted as a single partition or a disk can be devided into mutilple partitions. When a disk is divided into more than one partition, you end up with a hard disk that shows as two disks in Windows, each with their own drive letter assigned to them.


Data on the disk is written into the sectors and each little part of the sector can be magnetized to equal a 1 or demagnetized to equal a 0. A special table is used to keep track of where data is on the drive to help the computer locate data fast and efficiently. Different operating systems will configure hard drives using different formats. Microsoft Windows uses FAT (File Allocation Tables) and NTFS (New Technology File System) which is the most widely used today. NTFS has been the default format since Windows XP. These days FAT is still used on USB drives in a format called FAT32 while most Windows computers use NTFS for their internal hard drives. 

Data stored on a hard drive is kept long term even when the computer is turned off. This is where your operating system files are kept. We will be discussing operating systems shortly. The hard drive is also where applications are installed and where all data is stored long term on a computer. Some systems have 2 or more hard drives. Sometimes the two hard drives work independently to add more storage space. Other times the hard drives work together as redundant drives. When two hard drives work together to create redundancy in the event of a failure or or to expand a volume across more than one disk, this is known as RAID ( Redundant Array of Independent Disks.) We will talk more about this in a later lesson.

There is also another kind of hard drive called a Solid State Drive or SSD Hard Drive. These drives, unlike the drives with internal spinning disks, these disks do not have any moving parts. They work more like a USB thumb drive, but rather than being removable and physically installed inside the computer. These disks are much faster and less prone to failure because there are no moving parts. They are currently quite a bit more expensive which is why not all computers come with these yet.  



RAM or (Random Access Memory) is very fast memory that allows the processor to access the information much faster than it can on a hard drive. Read write times are extremely fast, however any data stored in RAM is lost as soon as the computer system is shut off or loses power, which is why we still need a hard drive. The more RAM a computer has, the more data the processor can have fast access too. This is why some computers with lower amounts of RAM may appear to be slow even if they have a fast processor.  Learn more about RAM by clicking here: RAM 

RAM is not to be confused with ROM (Read Only Memory) which is a chip, disk or device that has information permanently stored on it. The computer can read the data only and the ROM cannot be written to by the computer system. Some Compact Disks (CDs) are read only and are also known as a CD ROM.



A processor or CPU (Central Processing Unit) is the piece of electronic circuitry that performs mathematical functions, input/output operations, logic and controls based on the instructions it receives from the operating system or programs. Most CPUs are contained on a single chip. This are known as microprocessors. Modern CPUs have multiple cores on a single chip. Some systems like servers may have multiple processors each with multiple cores to aid them in processing a lot more data a lot faster than a standard PC or workstation.

Operating Systems


An Operating system is system software. It sends commands to the hardware telling it what to do. Software is loaded on top if the operating system so the operating system acts as the middleman between the hardware and the software. It also helps translate the language you understand into and from the language a computer understands (binary code). An operating system will tell the computer how the hard drive should be formatted, what hardware is available, how to access the hardware, which users can log in and which programs can run.

Microsoft Windows, Mac OS X, Linux, Unix, Android and Apple iOS or all operating systems. These are not all of the operating systems available but they are the most popular. Some operating systems such as on mobile phones and tablets are designed for just one user at a time. Some operating systems allow multiple logins from many different users at the same to to access shared data or programs.  



Software is basically the programs that you use on a computer. Everything from a web browser, to work processors and spreadsheets are all software applications. These install on top of the operating system and communicate with the operating system so that they know what to display on the computer screen, how and what to send to a printer and what data is a stored on the hard drive.

To learn more about this topic, please take our PC repair course or our CompTIA A+ course. If they are not yet available, they will be coming soon.

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