Evolution of computer systems.

Different Types of Computers. Тhese computers come in many sizes and shapes that perform different functions which is useful in our daily lives. You are using a type of computer even when you withdraw cash from an ATM (Automatic Teller Machine) or scan groceries at the shop, or use a calculator.

The computers can be mainly classified into four categories as briefly described below. This classification is done based on the size and the data processing power.

• Microcomputers: most common type of computers in the society. Can be used at yourworkplace, at school or on your study desk at home. Used by single user at a time. Small in size. Also called Personal Computers (PCs).

• Minicomputers:used by multi-users. In the middle when the computers are ranged fromsmallest to largest. Used in laboratories.

• Mainframes:Largest in size. Capable of handling and processing very large amounts of dataquickly.

• Super computers:Used for performing complex scientific and numerical computations suchas weather forecasting, fluid dynamics, nuclear simulations, theoretical astrophysics.

Different Types of Personal Computers (PCs).Personal Computer (Mostly referred to as PC in the community) is designed as a more user-friendly device to be directly used by the end-user rather having an especially skilled separate computer operator. It is less expensive compared to other types of computers listed above. PCs come in different forms as listed below and we will have a description on each form of PC separately.

It is noticeable that only few famous forms of PCs used today are listed below and the list may be extended by adding many more in the future with the advancement of the technologies. Desktop, Laptop, Netbook, PDAs, Wearable Computers, Tablets,

Desktop PCs.Usually the Desktop computers are placed in a fixed location and the name has derived as it is intended to be sitting on a top of a desk. A monitor, mouse, and a key board can be seen as parts of a typical desktop computer. These computers consume low power and cost effective than the laptop computers that will be described next. The spare parts are readily available and less expensive.

Laptop Computers.Laptops are similar to desktop PCs in operation, but designed for mobile use. Capable of operating on the battery power and the battery can be charged with the external power adaptor. An in-built keyboard, Liquid Crystal Display unit (LCD screen), a touch pad (also known as track pad) to act as the mouse are the commonly seen components. However, a mouse can be also used instead of the touch pad. Laptops are obviously smaller in size and weight less than the desktop PCs. Therefore, it is difficult to access its internal hardware thus difficult to upgrade as much as a desktop. But adding more RAM or Hard Drive is possible (You will learn about RAM and Hard Drive in next session). Built-in web camera is a common feature of a modern laptop computer and these laptops come in different weights, sizes, performances, speeds, and a layman may differentiate them specified by the diagonal distance of its display unit.

Netbook.Netbooks belong to the laptop family, but are inexpensive and relatively smaller in size. Though the set of features and the capacity of netbooks were lesser compared to regular laptops at the time of introducing them to the market, nowadays the netbooks come in advanced features and in high capacities as similar to modern laptops.

PDAs.Personal Digital Assistants (PDAs) are handheld computers which are also called palmtop computers due to its size which is smaller enough to keep it on your palm. Most of the PDAs are pen-based and come with a stylus (a writing pen) to be used as the input device which is sensitive to its touch screen. Most of them can access the Internet by means of Bluetooth or Wi-Fi facilities. PDAs allow you to organize your personal or business work and to manage your tasks through its facilities. It may be used as a Cellular phone to send and receive calls, to search in the web, to download and play audio/video files, to send/receive e-mails, to type in a text editor to jot down notes or write a document, take pictures or record videos, etc.

Wearable Computers.The computers that can be worn on the body are known as Wearable computers. There is a constant interaction between the computer and user. These computers are mostly used to track human actions when the hands and other sensory organs are engaged in other activities. And used with applications such as behavioral modeling systems and healthcare monitoring systems.

Tablets.Tablets are mobile computers larger than PDAs and smaller than Laptops described above. Usually operated by its touch screen and no formal key board are used. The people using them spent most of their time outside and would not have access to a keyboard or mouse.