1. What is a computer ? A computer is a programmable electronic device that processes data following a set of instructions to produce information which it can output or store for further use.

2. Types of computers  Computer systems are classified on the basis of system performance, which affects physical size and cost.  Given the rapid pace at which computer technology is changing classifying computers on this basis is very difficult.

3. Personal computers  Personal computers also sometimes called microcomputers, they are the most common types of computers.  They come in many different shapes,size and colours depending on the manufacturer.

4. Laptops  A laptop computer is a portable version of a PC, equipped with a flat liquid crystal display (LCD).  The two main types of Laptop computers are notebooks and sub-notebooks. 

5.  Personal computers are designed to be used by one person at a time and fit on an office desk, hence sometimes called ‘desktop computers’.  A PC computer consists of a keyboard, a mouse and a display screen.

6. Minicomputers  Minicomputers have become outdated and are rarely used today.  Minicomputers are designed to support more than one user at a time.  It possesses large storage capacity and operates at a higher speed.  The mini computer is used in multi-user systems in which various users can work at the same time.

7. Mainframes  Mainframe computers a very powerful and therefore very expensive.  Mainframe are systems that offer faster processing speeds and greater storage capacity than a mini computer.  They are found in large organisations such as banks, government agencies and insurance companies.

8.  They perform tasks that require a lot of computational power; typically bulk data processing such as censuses and consumer statistics.

9. Super computers (Monsters)  A supercomputer is a type of computer that has the architecture, resources and components to achieve massive computing power.  They are typically used for number crunching in scientific simulations and scientific research.

10. Tablet Pc  A Tablet is a computer that looks like a notebook computer except that data can be entered through a keyboard or touchscreen.  The data can be entered through the digitising tablet with the use of a special pen call stylus

11. Electronic organisers & palmtop computers  An electronic organizer is a small calculator- sized computer,  often with an in-built diary application but few other functions such as an address book and calendar.  It normally has a small alphanumeric keypad and an LCD screen of one, two or three lines.

12. Embedded computers  An embedded computer is a special-purpose computer used inside a device and is usually dedicated to specific functions.