04.1–What is a computer?-2012/01/16

This article goes back to the basics and describes what a computer is. Most of the older generation and a lot of the newer generation don’t really understand what a computer is. Therefore, when they read documents and articles about computers they quickly stumble on computer technical words that they don’t have a clue what they mean. This article is for them.

It will explain the basics about computers in laymen’s terms, with analogies to a car or a person’s brain. Like with any analogy, they may not be technically precise but they convey the concept. Hopefully the next time they lock at the specification sheet of the computer they want to buy, they will understand the specifications describing the different components of that computer. In a follow on article, I will provide an approach the compare one product to the next so that you can evaluate the relative performance between different products. All this applies to all computers including PCs, tablets, smartphones and the like.


A computer is an electronic device incorporating the following components:

  1. a processor to execute instructions supplied by software,
  2. main memory to store the computer instructions and the data it is working on,
  3. auxiliary memory to store all of the computer software and all the computerized user data,
  4. input and output facilities (screen + keyboard + microphone+…) to communicate with the user,
  5. an operating system, such as Windows 7, to operate and manage all of the above.

Computers come in many forms: personal desktop and laptop computers, tablets, smartphone, GPS, most of the instruments in use today, etc. The expressions above in bold are main components of computers and will be explained in the following lines.

Bits & Bytes

All of the data (each letter of your name) and each element of instructions (software) is represented and stored inside the computer in groups of eight “bits” characters called “bytes”. A byte is a certain combination of eight bits that are either ON or OFF (1 or 0). So, for example the letter “A” would be a combination looking like “10010101” (which is not the right combination but shows the point). Thus, everything inside a computer is represented with “1” and “0”.

Main memory

To do work the computer must have data and instructions to work on that data available. The “main memory” is the memory that stores all the data and the instructions that the computer needs to work with at that time. Main memory is made of electronic circuits that can store the “1” and “0” that make up the data and the instructions that the computer needs to work.

The Processor

The processor is like the engine in a car. It’s the engine that powers the computer. The number of “core” is like the number of cylinders you have in the car. In general, the more cylinders you have, the more powerful is the car. It is similar for a computer, the more cores the more power it has. Its clock speed is equivalent to the RPM in your car. Generally, the more RPM your car turns at, the more power it generates.

When we get into how to evaluate the power of a computer in another article, we will get into more details about these elements and explain how it is a combination of both the number of cores and the clock speed plus other factors that determines the power of a processor. For the time being, let just say that the processor is the computer engine. It is the engine that executes the computer instructions contained in the software on the data to produce the results.

The main memory and the processor are welded on an electronic circuit plate called the main board. The main board is the main circuitry of the computer. Other components attach to the main board as we will see later.

Auxiliary memory

The speed of the main memory is crucial to the speed of the computer. As in all things, the fastest the memory the more costly it is. So to maintain the cost of a personal computer at reasonable level manufacturers try to limit the amount of main memory. On the other hand, the more main memory you have the more powerful your computer will be.

Since only a miniscule portion of all your data and software needs to be in memory during the execution of the instructions you need a cheaper memory type to store all the rest of that data so that it will be readily available when the computer needs to work on it. For this, we use auxiliary memory. The most common form of auxiliary memory is a hard drive. Therefore, all of your data and software (instructions to be executed by the computer) are stored on your hard drive and available at all time to be brought into main memory to be worked upon.

Another example of the difference between main memory and auxiliary memory is our brain. In our brain’s memory we have the name and images of hundreds of people, but at any one time we can only think and talk about a few at max. When we want to talk about the others our main memory goes and gets from our auxiliary memory the information and images about the latest person we are talking about. It is the same for computers. They work on one thing at the time but are so quick it may give the impression that they are doing a lot at once.


Even if the hard drive is inside the computer frame, it is not part of the main board circuitry but attached to it. This why it is called a peripheral. Other peripherals are the screen, the keyboard, the mouse, the printer, the CD/DVD player, etc. Peripherals service the computer and are used by the humans to interact with computers.

The software

Since a computer is just circuitry designed to accomplish certain limited operations, it needs instructions. These instructions are provided through software. Software contains the instructions to make the computer do productive work. There are two main types of software: the operating system software and the application software.

The operating system software

Since the computer circuitry can perform only a limited set of elementary operations, there are a lot of management functions that a computer must do to execute the simplest task. For example: when you click on the mouse button on a certain position on the screen, the computer must interpret the electrical signal received from the mouse, determine what was on the screen at the exact location the pointer of the mouse was at on the screen, then it has to associate that position with instructions on what your click meant (right, left click, double click,…), then is has to communicate that meaning to the application software which in turn may ask for some data on the hard drive, then the computer must send a signal to move the hard drive arm to the exact location where that data is on the disk, and so on and so forth. As you can see, one little click on the mouse may results in hundreds of little actions inside the computer.

To take care of all of these basic computer functions requires a set of basic computer instructions. These are at the core of the operating system software. Microsoft supplies this software and it is called Windows 7. So when you see Windows 7, it simply means the software that takes care of all of the basic computer operations and management.

The version of the operating system software is also important. The latest version generally incorporates more functionality. There are significant differences between Windows XP and Windows 7. It is important to always keep your operating systems updated and at the latest version to fully take advantage of the latest functionality. These days, updates are often done automatically over the internet if your computer is properly configurated.

The key thing to remember is that the personality and screen look of each computer is determined by its operating system. The more user friendly the functionality of the operating system is, the easier it will be for the end-user to perform work on that computer.

The application software

The operating system makes the computer easy to use for you but it does not execute any task like a word processor, a spreadsheet, an accounting softyware, etc. These tasks are done by the application software. Each application software does pre-determined tasks that are described in their specifications. You want personal accounting, you use a Quicken like application. There are a great number of application software suppliers as there is a large spectrum of task end-users want to accomplish.


All of the above components are summarized on the following diagrams.

Let’s summarize and add specific known products to each component so that you can relate to expressions you have heard before but maybe did not fully understand.

Main memory

The active brain of the computer. It is made of circuit memory. When you hear that a computer has 4 GB (Giga Bytes) meaning 4,000,000,000 positions of memory they are talking about main memory. The first computer I worked with, in 1967, only had 4,000. This tells you immediately that this primitive computer could not accomplish compared to today’s computers.

Auxiliary Memory

The passive brain of the computer that can be called upon at any time to supply data and instructions to be processed in main memory. It also stores all of the operating and applications software to be copied to main memory whenever it is needed for execution. When you hear that the computer has a 500 Gb hard drive, it means that you can store up 500,000,000,000 characters of data and software on that computer auxiliary memory. Up to now, auxiliary memory was mainly hard drives, but with the lower costs of circuit memory more and more device, mainly tablets and smartphones are using circuit memory as auxiliary memory allowing manufacturers to package a lot more functions into miniature devices. As prices continue to go down circuit memory will eventually replace hard Drives for auxiliary memory. Other auxiliary memories include SD cards, miniSD cards and microSD cards. You can now add a 32,000,000,000 bytes micro SD card, way smaller than a dime in size, into a smartphone as auxiliary memory. Those are also used in digital cameras and other electronic devices.


The computer engine that does the computing work. Intel with its I3, I5 and I7 processors, is the main computer processors provider, followed by AMD. On tablets and smartphones, a number of new comers, such as Nvidia and others, have joined the race. Peripherals

Devices that allow the end-user to communicate with the computer. They are: hard drives, mouse, screen, printers, etc.

Operating system software

The software that runs and manages the computer and gives it a personality. This is a key part of the computer since the ease of use and the functionality are provided by the operating software.

Here are the names:

For personal computers: Microsoft Windows 7 for the most common PCs, and Apple Mac OS X for the Apple PCs.

For tablets and smartphones: Apple iOS5 for Apple’s iPhones and iPads, Google Android (different versions such as Gingerbread and others) for most of the other products with the exception of: BlackBerry’s OS, Nokia Sybian and Microsoft Windows Mobile, all trying to join the race.

So when you are evaluating a tablet or a smartphone, other than the phone hardware, you are mainly evaluating that phone operating system and the applications that the manufacturer has added.

Now that you know what a computer is, when you hear the following description of a product:

  1. Samsung Galaxy Note GT-N7000,
  2. 1.4 GHz (Giga Hertz) dual-core A9 SoC Processor,
  3. 1 Gb RAM,
  4. 16Gb flash memory,
  5. Up to 32 Gb micro SD removable storage,
  6. Running Android 2.3.6 (Gingerbread),
  7. 1220×800 px, 5.3 in. HD super Amoled screen,

You know that it is a smartphone (which is a computer) that:

  1. It is made by Samsung, fits in the Galaxy series, is the NOTE GT-N7000 model,
  2. Its main processor has two cores (two cylinders) and runs at a speed  (RPM) of 1.4 Giga Hertz,
  3. It has 1,000,000,000 position of main memory,
  4. It also has 16,000,000,000 position of auxiliary memory,
  5. You can add another 32,000,000,000 positions of auxiliary memory with a micro SD card,
  6. The phone personality is provided by Google Android version 2.3.6 code name Gingerbread,
  7. The screen peripheral has 1220×800 pixels (dots density), is 5.3 in. diagonal and is HD (like an HD-High Definition TV) with the latest screen technology called Super Amoled.

It’s that simple, now that you have learned the main components of a computer.

You can apply the same approach to understand the specifications of a personal computer or any other device.

In a coming article, I will cover how to evaluate the importance of each feature in order to assess the overall performance of a computer product you may be planning to buy.

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