How your computer works

Let’s decode computers together!

Oh how we love our computers. We can listen to music, stream our favorite shows and movies, and play some great games. For this to happen, a computer needs plenty of parts to work in unison.

In this lesson, we will uncover the basic parts of a computer, and what part they play. You may learn a thing or two about how these parts have evolved over the years too! We will also look at an example of how the parts work together when running Microsoft Word.

The Motherboard

If you’ve ever seen the inside of a computer, you’ll notice what looks like a board with a lot of chips, pins, and wires connecting into it. This board is called the motherboard. The motherboard is the communication hub for all your parts in the computer. While there are a lot of parts, let’s look at some of the most critical pieces.

Buses: A motherboard has multiple buses inside it. These buses are wires that help data connect to multiple parts or subsystems within the entire computer. There are two main buses in the motherboard:

  • System bus: The system bus connects your CPU to the RAM (memory) connected to the motherboard.
  • I/O bus: The Input/Output bus connects your peripheral devices to the CPU. Examples of peripheral devices include your keyboard and monitor.

Computers can have multiple additional buses, including buses for any external devices, such as audio cards.

Chipsets: As the name would suggest, chipsets are a set of chips within the motherboard that control the communications between the CPU and other parts of the computer, such as your RAM, hard drive, and keyboard and mouse.

If you ever get the chance to see older motherboards, you’ll see a whole lot of chips covering the board. Each chip was responsible for the communication between the CPU and only one other part of the computer. On early motherboards, there would be one chip just for the hard drive!

As technology progressed, motherboards began having northbridge and southbridge chipsets. The northbridge chipsets connected the CPU to critical components, such as your computer’s RAM and graphics cards, if your computer was built for playing games. The southbridge oversaw connecting non-critical components to the CPU, such as audio cards and networking cards.

In modern motherboards, things are far different. Instead of having a northbridge and southbridge, the CPU now acts as the northbridge. In 2011, Intel created their newest generation of CPUs at that time. One of the biggest additions to the new generation was the addition of adding the northbridge chip onto the processor’s die. If you want to learn more about what a processor die is, click here.

This means that CPUs now can communicate with the other critical components of your computer without having a middleman. This has lowered latency, meaning that some tasks the CPU executes can finish faster. We’ll go over what the CPU does a little later in this lesson.

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So, where has the southbridge gone to? If you Google motherboards, you will see something like “Z370” or “X370” motherboard. These are actual chipsets from either Intel or AMD (Intel is the Z, AMD is the X) that are placed onto the motherboard itself. These chipsets are the southbridge of the motherboard. If you want to build your own PC, it’s critical that you look at what chipset the motherboard is, as you will need to find CPUs that are compatible with these chipsets (otherwise, you’ll have an expensive paperweight).


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In the motherboard section, we mentioned the CPU a few times. CPU stands for Central Processing Unit. The CPU is the brains of the computer and is by far the most important part of your computer. Without a CPU, your computer won’t run!

The CPU oversees three important steps:

  • Fetch: When a program starts, the CPU will grab the instructions to run the program.
  • Decode: Once the CPU has the instructions, it will decode them and fetches any data necessary.
  • Execute: The CPU will start executing the decoded instructions.

We will go over in detail what each step does a little later in this lesson.

If you look at information about a CPU on the manufacturer’s website, you will see some piece of information labeled “clock speed”. A CPU performs instructions in clock cycles, which is how long between “clock ticks”. Clock ticks for a CPU aren’t based on how many seconds have passed, however. Instead, clock ticks are measured in hertz. This is known as clock frequency.

When you look at the clock speed, you will now often see something like 2.5 GHz. A single clock cycle is 1 hertz each. So, a 2.5 GHz processor will have 2.5 billion cycles per second. Most instructions only take 1 cycle to complete, so having a faster processor helps*.

To give an idea of what a clock tick looks like, look at the photo below. As you see, the tick begins with a “rising edge”. This means the signal from the clock is beginning to change from a 0 to a 1 since there’s an electric “pulse”. When the tick peaks, the value is now a 1. The signal will then start to transition back to a 0 after the pulse ends. This transition is known as the “falling edge”. The amount of clock ticks per second depends on the clock speed of the CPU.

Clock cycles don’t represent 1s and 0s for data. These cycles are more set and keep the pace for instructions to execute, so think of them as a timer.


Photo by Valentine Tanasovich on

If you read information about computers that are for sale, you’ll see some details about how much memory the computer has. The memory in a computer comes from Random Access Memory, or RAM for short. Whenever you open a program on your computer, the instructions to execute the program, and any data necessary, is stored in the computer’s RAM.

RAM is “random access” because the information stored in RAM can be accessed randomly, rather than in sequential order, like on a CD-ROM.

When reading RAM packaging, you’ll see things like the amount of memory available for each RAM stick, and the read-write speed. Of course, having more RAM available allows you to run more applications at a time, since each program needs to have a chunk of your available memory.

Simple tasks, such as writing a paper in Word, or creating spreadsheets in Excel, don’t require a whole lot of RAM, so you can likely get away with having only the minimum requirements that your Operating System (Windows, for example) needs. However, if you want to run graphically intense video games, or do anything related to video editing or photo editing, you’ll want more RAM, since these programs have far more instructions that need to run.

Regarding read-write speed, getting faster speeds isn’t necessarily better. If you look at Intel’s information regarding the processors in the memory specifications section, you’ll see it can work with DDR4 RAM up to 2666 MHz. So anything faster really won’t be beneficial, unless you decide to overclock*. As you can see in this video, overclocking to get more RAM speed available doesn’t always work.

*Overclocking is increasing the clock speed of a CPU or RAM beyond the specifications of the manufacturer. While manufacturers are giving consumers more opportunities to overclock their products, it’s recommended you only do so if you absolutely know what you’re doing. Improperly overclocking any critical component can be disastrous.


Photo by Aza Bo on

After a long day at the office, you make sure to save any progress you made on reports or projects so you can pick up from where you last left off. This makes life a lot easier, since you won’t have to start from scratch over and over again. Hard drives and Solid State Drives (SSDs) allow us to save a lot of information. We will explain hard drives and SSDs in another lesson.

As you know, data in computers are made up of 1s and 0s. When we tell the computer to save a Word document, we are saving the current state of the program and data the programming is using. In programming, this is called serialization. In basic terms, serialization takes the current object (Word document in this case) and turns it into a stream of bytes, which in this case is a Word file. Programs have certain files extensions, such as .docx for Word (Word 2010 or later). When you double click on a specific file, your Operating System has a directory that tells it which program is associated with certain extensions.

Putting it all together

To tie all the pieces together, let’s look at an example. Let’s assume you have a document you have been working on in Word. After getting back to the office, you navigate to where you saved the file, and double click it to open it back up.

Your computer will see you are opening a Word document and will start up Word. During the starting process, the instructions to run Word, along with the saved data, will move from your storage disk (hard drive or SSD) onto the RAM. The RAM now holds all the necessary pieces for the CPU.

The CPU will now begin fetching Word’s instructions from the computer’s RAM, one at a time. After it receives the current instruction, it will start to decode something called the opcode. The opcode is simply the operation the CPU needs to run for the specific instruction. If the CPU finds it needs specific data for the instruction, it will fetch the data located in the RAM.

Once the instruction has been decoded, the CPU will start executing the instruction that it currently has. In the case of Word, this can be examining which key you pressed on the keyboard, and determining what to do with this input based on the instruction, such as showing which letter you entered. Once the CPU completes the current instruction, it will move to the next instruction, decode it, and execute it.


While there is a lot more to how a computer works, this is a basic breakdown of what happens within a computer. The computer needs all these parts to work together for programs to work as they’re intended.

The motherboard oversees communication between all parts and transporting critical data to where it needs to go. The CPU gets programs to run. The computer’s memory stores all the instructions and data for programs so the CPU can quickly get what it needs to run programs. And the storage devices, whether it’s a hard drive or an SSD, allows us to save the progress of files so we can continue where we left off.

It will certainly be interesting to see where technology takes us as these parts continue to evolve into smarter technologies.


Klein, Matt. “What Is a ‘Chipset’, and Why Should I Care?” How, How-To Geek, 17 Aug. 2017,

Wilson, Tracy V., and Ryan Johnson. “How Motherboards Work.” HowStuffWorks, HowStuffWorks, 20 July 2005,

Strickland, Jonathan. “How Sandy Bridge Works.” HowStuffWorks, HowStuffWorks, 24 Mar. 2011,

Martindale, Jon. “People Always Say You Should Upgrade Your RAM. But What Is It, Anyway?” Digital Trends, 28 Aug. 2019,

Null, Linda, and Julia Lobur. The Essentials of Computer Organization and Architecture. 3rd ed., Jones & Bartlett Learning, 2012.

“What Is RAM (Random Access Memory)?” Computer Hope, 3 Sept. 2019,

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