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The core of computer

Tahfimul Latif Hacker Noon profile picture

@tb.Tahfimul Latif


In this story I will speak about the lessons which I acquired from my software engineering class. I will touch upon the introduction and continue this story as a series to reflect my understanding of the Java language.

A computer is made up of two components:


  1. Motherboard
  2. CPU
  3. GPU
  4. RAM
  6. HDD
  7. SSD
  8. Peripheral Devices
  9. Power Supply

Software Layers

  1. BIOS (Basic Input Output System)
  2. Device drivers
  3. Operating System
  4. Applications

Lets break down each of these components



You can think of a motherboard as a board with millions of wires attached. All hardware connect to the motherboard through these connections and communicate within it. The term used to describe the connections is System Bus.

CPU (Central Processing Unit)

This is the brain of all computers. It is made of transistors. When transistors are arranged together, they form gates. These gates can perform Boolean operations. Some Boolean operations are OR, NOT, AND and NAND. The gates only accept two inputs, on or off, true or false, 1 or 0 which are used to perform the Boolean operations.


GPU (Graphics Processing Unit)

Ever wonder how graphics such as video are displayed on your computer’s monitor? This job is handled by the GPU. Similar to the CPU, GPU have a unique set of memory called the vRAM which it utilizes while processing graphics.


RAM (Random Access Memory)

Vast amounts of processes take place in an operating system. Some of them require temporary storage. RAM is a storage device that is responsible for storing temporary data. Once, a computer is shut off, this temporary data vanishes unless saved to a permanent storage device such as HDD.


EEPROM (Electronically Erasable and Reprogrammable Read Only Memory)

Before a computer loads into the Operating System, several operations occur. The EEPROM contains instructions for these operations (a.k.a. BIOS). In the early days, data in this chip were set to be permanent from where the acronym ROM arrives.

HDD (Hard Disk Drive)

Unlike RAM, this is a permanent storage device. This is where things like the Operating System and personal files are stored. HDDs contain a spinning disk where data is stored.

SSD (Solid State Drive)

Compared to HDDs, data in SSDs are stored electronically. It provides faster read and write speeds, allowing more computing power. However, SSDs cost a fortune. For example, today’s computers require at least 256 GB of permanent storage. A 256 GB SSD will cost around $100. Whereas, a 1 TB HDD costs only $50.

Peripheral Devices

Any device that externally connects to a computer via a USB or other forms of connections are considered a peripheral device. A mouse is a great example of this tier because it connects via USB connection.

Power Supply

A power supply ensures the right amount of power is received by the motherboard.

All of these components sit inside a case.

Via a video cable, the monitor is connected to the motherboard. Thus, the reason graphics appear in the monitor. Video cables come in several formats. The most common are HDMI and VGA.

Software Layers

A computer consists of many hardware. However, they only come to use when software are created to run them. That’s where the software layers come in.

BIOS (Basic Input/Output System)

This is the very first layer of the all the software layers. In order to understand its job, lets find out how a computer powers on.

After pressing the power button on a computer, several events occur.

  1. The very first thing that happens is that the power supply tests the power coming in.
  2. Once it confirms that the power is good, the power is sent to the motherboard.
  3. Then the CPU powers on. It immediately locates and activates the BIOS. This makes location of the EEPROM chip extremely critical. If the location of the EEPROM is different than what the CPU knows or if it goes corrupt, the computer will not boot up. The EEPROM is usually situated in the lowest of all memories.
  4. The BIOS first starts up the POST (Power On Self Test).
  5. Under the POST, several sub-processes occur.

A. First the BIOS communicates with the CMOS, which checks to see if the components are where they should be.

B. Then, BIOS loads the basic drivers.

C. Next, the POST sends digital signals using the System Bus to all the components, checking to see if they work properly.

D. After that, the POST uses the basic video settings to execute a low graphic screen into a monitor. If all goes well, a beep comes on.

E. The POST hands off to the bootloader.

6. The bootloader searches for the operating system and loads it.

7. Finally, the operating system loads up.

8. The operating system loads the more sophisticated drivers which efficiently communicate with components.

History of BIOS

Gary Kildall first invented BIOS in 1975. The early version of BIOS chip (a.k.a. ROM) were not re-programmable. Then UV (Ultraviolet) EPROM (Eraseable Programmable Read Only Memory) chips came to light which had data written to it using UV light. It came in one chip, shaped rectangular. (See image below)

Source: aralabs.com

However, UV-EPROMs proved to be inefficient when the BIOS had to be reprogrammed. The chip had to be removed and erased using UV light and data had to be rewritten using UV light. The next version of the BIOS chip was known as EEPROM. This chip could be programmed electronically and eliminated the the use of UV light. It came in the same rectangular form (DIP) as the UV-EPROM chip. (See image below)

Source: aralabs.com

A third version was out due to so many components that needed to be packed into the motherboard. This square shaped EEPROM chip was known as PLCC with pins on all four sides. It also came with firmware hub invented by Intel. The firmware hub, loaded data from BIOS to RAM and CPU read data from RAM.(See image below)

Source: aralabs.com

Today, computers take advantage of smaller, more efficient and cost effective, SPI FLASH EEPROM chip. It comes in DIP and 8-pin forms. Unlike the previous chips, these modern chips communicate directly to the RAM. (See image below)

Source: aralabs.com

Device Drivers

Drivers can be thought of as a method or protocol which enables a computer to speak to another device. There are many types of drivers for all kinds of hardware. For instance, drivers for keyboard, mouse, flash drives, video card and so on.

Operating System (OS)

This is the graphical user interface (GUI) which you see when a computer boots up. Operating Systems such as MacOS and Windows maintain user-friendly and easy to use GUI in conjunction with complex code which enable the GUI functions.


A novice may turn on a computer to use applications. Applications come in various types and sizes through which we automate various tasks. Today, they are usually coded using high level languages such as C or Java.

Visit my portfolio website: tahfimul.github.io/TP./


  1. http://www.arlabs.com/bios_history.html
  2. https://superuser.com/questions/707254/where-is-the-bios-stored
  3. https://www.youtube.com/watch?v=nTVVYsd6Cdg
  4. Litvin, Maria, and Gary Litvin. Java Methods: Object-Oriented Programming and Data Structures. 3rd ed., Skylight Pub., 2015.
  5. http://www.skylit.com/javamethods/JM-Chapter01-www.pdf


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