Introduction to computer and computing

What is a Computer?

A computer is an electronic device that works under the control of instructions stored in its own memory. It can:

1. Accept data (this is called input).
2. Process the data according to specific rules.
3. Produce information (this is called output).
4. Store the information for you to use in the future.

Functionalities of a Computer

In simple terms, any computer performs five main functions:

• It takes in raw facts and figures, which we call data.
• It stores this data and the instructions on how to use it.
• It processes the data, turning it into useful information.
• It shows you this new information as output.
• It controls all these steps to make sure they happen correctly.

Data, Information, and Knowledge

It is important to understand these three related ideas:

• Data: These are raw, unorganized facts and symbols. By itself, data does not mean much. Example: The number "39.1".
• Information: This is data that has been processed and given context to make it useful. It answers questions like "who, what, where, when". Example: "The patient in Bed 5, Jane Auma, has a temperature of 39.1°C at 10:00 AM."
• Knowledge: This is the understanding you gain from information. It helps you make decisions and answers "how" questions. Example: "A temperature of 39.1°C indicates a high fever, so I need to administer paracetamol as prescribed and monitor the patient."

Computer Components: Hardware and Software

Every computer system is made of two main parts that must work together: HARDWARE and SOFTWARE.

Hardware

Hardware refers to the physical parts of the computer system that you can see and touch. Examples include:

• External parts: Monitor (screen), keyboard, mouse, printer, speakers.
• Internal parts: Hard drive, motherboard, memory (RAM) chips, graphics card, sound card.

Software

Software is a set of instructions or programs that tells the hardware what to do. You cannot physically touch software.

A Closer Look at Hardware

Input Devices

These devices are used to enter data and instructions into the computer.

• Keyboard: For typing text and numbers. The most common layout is QWERTY.
• Mouse: A pointing device used to select items on the screen.
• Scanner: Converts paper documents into digital files on the computer.
• Microphone: Captures sound and voice.
• Webcam: A video camera that feeds video to the computer in real time.
• Touch Screen: Allows you to input commands by touching the screen directly.

Output Devices

These devices display or present the results of the computer's processing.

• Monitor: The screen that displays visual information. Types include LCD and LED.
• Printer: Produces a paper copy of documents. Types include Inkjet and Laser printers.
• Speakers: Produce audio output.
• Projector: Displays the computer's screen on a large surface.

Inside the System Unit: The "Brain" and "Memory"

1. Central Processing Unit (CPU)

The CPU is the brain of the computer. It is the most important part, responsible for performing almost all of the computer's work. It is made of three main parts:

• Arithmetic Logic Unit (ALU): This part performs all mathematical calculations (addition, subtraction) and logical operations (like comparing if one number is greater than another).
• Control Unit (CU): This part acts like a traffic police officer. It directs and coordinates all the operations inside the computer. It fetches instructions from memory and tells the other parts what to do.
• Registers: These are very small, super-fast storage areas inside the CPU that hold the data and instructions it is working on right at that moment.

2. Primary Memory (Main Memory)

This is the computer's main working memory. It is where data is stored temporarily while the CPU is processing it. There are two types:

• RAM (Random Access Memory): This is volatile memory, meaning its contents are erased when the computer is turned off. It is the computer's short-term workspace. The more RAM a computer has, the more tasks it can do at the same time smoothly.
• ROM (Read-Only Memory): This is non-volatile memory, meaning its contents are permanent and are not erased when the power is off. It holds the basic instructions needed to start up the computer (the BIOS). You cannot normally change what is stored on ROM.

3. Secondary Memory (Storage)

This is where data and programs are stored permanently. It keeps your files safe even when the computer is off.

Other examples of storage include Flash Disks (USB drives) and Optical Disks (CDs, DVDs).

Units of Measurement

Storage Measurement

Computer data is measured in units called bytes.

• Bit: The smallest unit of data, either a 0 or 1.
• Byte: A group of 8 bits. One byte can store one character, like the letter 'A'.
• Kilobyte (KB): 1,024 bytes. (About one page of plain text)
• Megabyte (MB): 1,024 KB. (About one high-quality photo or a short MP3 song)
• Gigabyte (GB): 1,024 MB. (About one movie)
• Terabyte (TB): 1,024 GB. (Thousands of movies)

Speed Measurement

The speed of a CPU is measured in Hertz (Hz). This tells you how many instructions (or cycles) the CPU can perform per second.

• 1 Hertz (Hz): 1 cycle per second.
• 1 Megahertz (MHz): 1 million cycles per second.
• 1 Gigahertz (GHz): 1 billion cycles per second. (Modern computers are typically 2-4 GHz).

Types and Classifications of Computers

Computers come in many shapes and sizes.

• Personal Computer (PC) / Desktop: A computer designed for a single user, usually sits on a desk and is not easily portable.
• Laptop: A portable, battery-powered computer where the screen, keyboard, and system unit are combined into one device.
• Tablet: A very portable computer that is mainly a touch screen, with no physical keyboard.
• Smartphone: A mobile phone with powerful computing abilities, essentially a small computer that can make calls.
• Supercomputer: The largest and fastest type of computer, used for extremely complex scientific calculations, like weather forecasting or medical research.

Characteristics of a Computer

Computers are useful because of these key characteristics:

• Speed: They can process millions of instructions per second, completing complex tasks very quickly.
• Accuracy: They do not make mistakes unless given wrong data or instructions by a human.
• Diligence: They do not get tired or bored. They can perform the same task over and over again with the same speed and accuracy.
• Storage Capability: They can store huge amounts of information and retrieve it instantly when needed.
• Versatility: They can perform many different types of tasks, from writing a report to analyzing patient data to playing a video.

A Brief Note on Computer Viruses

A computer virus is a type of malicious software (malware) designed to spread from one computer to another and interfere with computer operation.

• Virus: A piece of code that attaches itself to a program. When you run the program, you also run the virus.
• Worm: A program that can copy itself and travel across networks without any human help.
• Trojan Horse: A program that looks like something useful (like a game or a helpful tool) but contains hidden malicious functions.

How to Stay Safe:

• Install reputable antivirus software and keep it updated.
• Be careful about opening email attachments from unknown senders.
• Do not download software from untrustworthy websites.
• Back up your important data regularly.