Chapter 2: Types of Computers

Development of PCs

3000BC Abacus ( manual calculating machine) 1643 First mechanical adding machine ( Blaise Pascal ) 1833 Babbage's difference engine ( automatic calculator ) 1896 Hollerith's automatic census tabulating machine ( using punched cards ) 1944 First electromechanical computer ( Mark 1 ) 1946 First programmable electronic computer in the USA (ENIAC) 1971 Microprocessor chip developed 1975 First microcomputer ( MITs Altair 8800 ) 1977 Apple II computer ( first personal computer sold in assembled form ) 1981 IBM introduced personal computer 1982 First portable computers 1993 Multimedia desktop computers, personal digital assistants 1994 Wireless data transmission for small portable computers

Desktop

A desktop computer is a personal computer designed for regular use at a single location on or near a desk or table due to its size and power requirements. The most common configuration has a case that houses the power supply ( motherboard, CPU, disk storage, a keyboard and mouse for input, and a computer monitor, speakers and often a printer for output. The case may be oriented horizontally or vertically and placed either underneath, beside or on top of a desk.

Notebook

A notebook computer is a portable computer that weighs 2 to 4 kilograms ( roughly the size of a thick note book, perhaps ps 35 by 20 cm ) They have a fairly large color screen ( about 30 cm across, a fairly large keyboard, usually with a small touch-sensitive pad which serves as a mouse ) Notebook PCs can easily be tucked into a briefcase or or backpack or simply under your arm ( can use power from an electrical outlet or rechargeable batteries. Usually just as powerful as a desktop but cost more than an equivalent desktop PC

Motherboard

A printed circuit board with a microprocessor as the central processing unit (CPU), memory, bus and other electronic components

Tablet

A tablet computer, commonly shortened to tablet ( a mobile device, typically with a mobile operating system and LCD ( Touchscreen Display) processing circuitry, and a rechargeable battery in a single thin, flat package. Tablets do what other PCs do but lack some I/O capabilities that others have. Modern Tablets resemble modern smartphones but are relatively larger ( with screens 7 inches (18cm) or larger measured diagonally and may not support access to cellular network.

Classification of computer

Classification is done on the basis of the system performance, which affects physical size and cost

Generations of Computers

Computers can be broadly classified into five generations These generations are based mainly on the basic electronic component that was used to build the computer

What are "Monsters"

Custom built super computers that are in need of a special technical team to maintain

Electronic Organizers

Electronic organizers are mainly used to store appointments, addresses and phone numbers and "to do" lists. Palmtop computers are more powerful Some mobile phones are powerful enough to act as very small personal organizers

Fourth generation (1971-present)

Fourth generation computers are based on the chip but with many more components packed inside. First we had large-scale integration (LSI) where hundreds of components were placed onto the chip. By 1980's very large integration squeezed thousands of components onto a chip. Ultra-large-scale integration (ULSI) increased that number of millions. Computer became even smaller, cheaper, much more reliable and their processing capabilities increased.

Types of PCs

Just like the categories of computers, PCs can also be classified based in size and cost Size of PCs from big to small Desktop Notebook Laptop Netbook Tablet Palmtop

Laptop

Laptop computers is a portable computer equipped with a flat display screen and weighing about 1 to 4 kilograms. The prinicipal types of laptop computers are notebooks and sub-notebooks

Mainframe

Mainframe computers are very large and powerful computers ( very expensive ) Mainframe computers are systems that offer faster processing speeds and greater storage capacity than a typical mini. ( it's like a smaller version of the super computer) A mainframe can handle more than a hundred users at a time. They are found in larger organizations ( banks, insurance companies and corporations ) They are individually built and can be tailored to the needs of the organization.

Minicomputer

Minicomputers have become outdated and are rarely used today. ( very popular in the 1960's ) Their cost, storage and processing capabilities were between those of a PC and a mainframe. They were mainly used in small manufacturing plants, research labs and businesses. Mini systems were usually designed to handle simultaneously the processing needs of multiple users. They allowed many users to share access to hardware through stations called terminals Minicomputers are mass produce in factory

Netbook

Netbook is a generic name given to a category of small, lightweight, legacy free, and inexpensive laptop computers ( introduced in 2007 ) Netbooks have 9-10 inch screens, weigh from 2 to 3 pounds, and sport keyboards sized from 80% percent to 95% of normal.

Palmtop

Palmtop gets its name because it fits in the palm of your hand are even smaller. ( less powerful than notebook and sub-notebooks ) They can fit into a shirt pocketing weigh perhaps 300 grams on average They might have a very small keyboard or a palm sized screen (sometimes in color) which can be written on with a special pen

Microcomputer

Personal computers (PCs) also called microcomputers, come in different shapes, sizes and colors. PCs are designed to be used by one person at a time ( can usually fit on a desk (desktop computer s) A PC consists of a system unit ( A key board, a most and a display screen and has all the functional elements found in any larger system ) It is designed to perform the input, control, arithmetic-logic, output and storage functions It can execute program instructions to perform a wide variety of tasks. PCs are mass produce in factory and some can be customized to the need of the computer. Software and hardware can be purchased to enhance the system

Sub notebook

Sub-notebook computer weigh about half a kilogram and can fit in a large jacket pocket Has a small screen, sometimes color, and a small keyboard without the mouse function. They can perform many functions of notebooks, but not to the same degree of complexity

Categories of computer from big to small

Super computer (number crunchers/monsters) Mainframes Mini computer Microcomputer (Personal computer (PCs))

Super computers

Super computers such as (Cray T3E-900) and (GRAPE-4 are the largest, fastest and most powerful computers present. Typically used for number crunching scientific simulations and scientific research Development in area such as ( energy, space exploration, medicine and industry ) Super computers are the most expensive computers in the world ( often costing millions of dollars ) Super computers can also be found in NASA

What are "terminals"

Terminals allowed many users to share the access to the hardware in minicomputers A typical terminal has a keyboard, a display screen and wire that connects the terminal to the computer systems.

First generation ( 1945-1956)

The vacuum tube or valve was the main electronic component of first generation computers This made the computer very large They contained miles of electrical wire, used a lot of electrical power and generated a lot of heat. Because vacuum tube were blown easily, processing was unreliable. Also each computer had a different binary coded program called machine language that told it how to operate. They made the computer difficult to program and limited its versatility and speed.

Fifth Generation (present-future)

These are computers that will be able to mimic many of the things that so far can on,y be done by humans. ( Fifth generation computers will be able to accept spoken word instruction ( voice recognition) and assist doctors in making diagnoses

Second generation ( 1956-1963 )

Transistors were invented in 1948 These formed the basis for the second generation computers. The computer became smaller, faster, more reliable and more energy-efficient than their predecessors The machine languages of the first generation computers were replaced by assembly language, allowing abbreviated programming codes to replace long difficult binary codes

Disk storage

Usually one or more hard disk drives, optical disc drives, and in early models a floppy disk drives)

Third generations ( 1964-1970 )

With the invention of the integrated circuit (IC) or chip computers became even smaller, faster, more reliable, more energy-efficient and cheaper than their predecessors. Another third generation development included the use of high-level languages which used English words and the base ten number system to program the computers. Third Generation Computers used Integrated Circuit (chips) Integrated Circuits are transistors, resistors, and capacitors integrated together into a single "chip"