Computer Types

a) On the basis of function/Activity

i) Analog computer
An analog computer is one that measures physical, continuous data such as temperature or pressure that fall along a continuous scale or variance in temperature of pressure. They give approximate result. For example an analog computer connects fuel flow measurements into quantities and price value.
Analog devices are speedometer, Seismograph, Thermometer etc.

ii) Digital Computer
The computer which accepts discrete (discontinuous) data is known as digital computer. Basically digitally computer counts digits which present numbers or letters.
Examples: IBM-PC, IBM compatibles

iii) Hybrid Computer
The data processing device, which uses both continuous and discrete data, is known as Hybrid computer.
Auto flight or Safe flight system is used in flight is known as Hybrid computer.

b) On the basis of brand / Manufacture

i) IBM-PC
The personal computer manufactured by the IBM (International Business Machine) company is known as IBM-PC.

ii) IBM-Compatible
The computers having the same functional characteristic of IBM Company are called IBM compatibles. (Assembled Computer)
iii) Apple/Macintosh
The computer developed & manufacture by Apple Company having different architecture and system known as Apple/ Macintosh computer.

c) On the basis of size / volume

i) Super Computer
Supercomputer are the most powerful and the fastest computer system, are used in weather forecasting, rocket launching, seismology, nuclear physics and so on. Examples: CRAY-1, CRAY X-MP, SX-2, HITAC S300 etc.

ii) Mainframe Computer
A Mainframe is the largest, fastest computer systems of general use having largest storage capacity; more then 100 people can work at the same time. Examples: IBM-1401, IBM-4300 HP9000model 3705/300 & 8705/400

iii) Mini Computer
Minicomputers resemble mainframe computers but they are comparatively small and less expensive.
Examples: IBM-AS/400/b60, HP-900, VAX-8842, Wipro-s68030 v, MIPS-II-52

iv) Micro Computer
A computer, which is based on microprocessor, is called a microcomputer. Types of Microcomputer are: 1. Desktop Computer 2. Laptop Computer 3. Palmtop Computer

d) On the basis of speed/model
i) XT (Extended technology) 8086, 8088 with speed 4.77 MHZ
ii) PC/AT (Personal Computer Advanced Technology) 80286, 80386, 80486. Pentium i, ii, iii, iv
iii) PS/2 (Personal System-2) other types of model from IBM since 1990.

The motherboard

The most important of any computer is the motherboard. The motherboard is the largest board of the computer system. It is also called system board. The motherboard is located on the left side of PC’s case on the bottom. It is usually green sheet of fiberglass with many chips, resisters, the heart of the computer i.e. power supply and contains many other organs of the computer system. It also contains the memory i.e. ROM and RAM and many other supporting logic circuits to make the complete work as a proper system. Instead of motherboard "IBM" refers to it as "System Board" or "Planer Board" but sometimes other manufacturer refers to it as ‘Logic Board". It accepts the CPU, memory, various plug-in peripherals, connectors and supporting circuitry. The motherboard defines the type of system by defining the type of processors it accepts, by the chipset features and by its architecture.
IBM decided that there should be used two different types of technologies, which were being used to make personal computer. They are:
Bus Based computers
Single Board Based computers
1. Bus based computers
These bus-based computers have used the main board as the backbone of the computer system. This bus board contains number of buses through which the data can be sent from one place to another and it also contains the number of slots onto which we can connect various different devices. Mainly the expansion cards are connected onto the expansion slots. In this type of bus based computer there are three buses. These are :
Address Bus
Data Bus
Control Bus
Address Bus :
Group of lines carrying the addressing information used to describe the memory location to where the data is being transferred.
Data Bus :
A set of lines used to carry the data.
Control Bus :
It is used for carrying a set of control signals that control the flow of data.
These all buses are provided on these boards. The main advantages of this type of board is that, whenever any part fails, the board on which that part is located can be removed and replaced with a working board, very easily and so it makes the maintenance of the system very easy. In these types of computers, different parts of a system such as main processor, memory, display card etc. are put on separate cards and connected to the main system bus through expansion slots.