1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

The Mainframe Computer – These are computers used by large organizations like meteorological surveys and statistical institutes for performing bulk mathematical computations. They are core computers which are used for desktop functions of over one hundred people simultaneously. A mainframe (also known as "big iron") is a high-performance computer used for large-scale computing purposes that require greater availability and security than a smaller-scale machine can offer. Historically, mainframes have been associated with centralized rather than distributed computing, although that distinction is blurring as smaller computers become more powerful and mainframes become more multi-purpose. The mainframe is sometimes referred to as a "dinosaur" not only because of its size but because of reports, going back many years, that it's becoming extinct. In the early years of computing, the original mainframes were housed in room-sized metal frames, which is probably where the name derives from. In the past, a typical mainframe might have occupied 2,000 - 10,000 square feet. Newer mainframes are about the same size as a large refrigerator.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

The Microcomputer – These are the most frequently used computers better known by the name of
“Personal computers”. This is the type of computer meant for public use. Other than Desktop Computer
the choice ranges as follows:

Personal Digital Computer

Tablet PC

Towers

Work Stations

Laptops

Hand Held Computer

A microcomputer is a complete computer on a smaller scale and is generally a synonym for the more common term, personal computer or PC, a computer designed for an individual. A microcomputer contains
a microprocessor (a central processing unit on a microchip), memory in the form of read-only memory and random access memory, I/O ports and a bus or system of interconnecting wires, housed in a unit that is usually called a motherboard.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

The Mini computer – Mini computers like the mainframe computers are used by business organization. The difference being that it can support the simultaneous working of up to 100 users and is usually maintained in business organizations for the maintenance of accounts and finances. A minicomputer, a term no longer much used, is a computer of a size intermediate between a microcomputer and a mainframe. Typically, minicomputers have been stand-alone computers (computer systems with attached terminals and other devices) sold to small and mid-size businesses for general business applications and to large enterprises for department-level operations.

The Super Computer – It is somewhat similar to mainframe computers and is used in economic forecasts and engineering designs. Today life without computers is inconceivable. Usage of different types of computers has made life both smooth and fast paced. A supercomputer is a computer that performs at or near the currently highest operational rate for computers. A supercomputer is typically used for scientific and engineering applications that must handle very large databases or do a great amount of computation (or both).

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

Hardware devices for input, processing, storage, output and communications

Input Devices

An input device is any hardware component that allows you to enter data, programs, commands and user responses into a computer. Some popular include keyboard, mouse, trackballs, and light pens, digital camera, scanner, and microphone. Table 1 summarizes a list of input, output and devices that are commonly used.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

Keyboard

This is the most common input device for home and commercial users. It is made up of a set of typewriter-like keys that enables you to enter data into a computer. Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. The keys on computer keyboards are often classified as follows:

Alphanumeric keys -- letters and numbers

Punctuation keys -- comma, period, semicolon, and so on.

Special keys -- function keys, control keys, arrow keys, Caps Lock key, and so on.

The standard layout of letters, numbers, and punctuation is known as a QWERTY keyboard because the first six keys on the top row of letters spell QWERTY.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

Output Devices

It refers to any machine capable of representing information from a computer. This includes display screens, printers, plotters, and synthesizers. Refer to Table 1 for a complete list.

a) Display screen

The display part of a monitor. Most display screens work under the same principle as a television, using a cathode ray tube (CRT). Consequently, the term CRT is often used in place of display screen. Abbreviation of cathode-ray tube, the technology used in most televisions and computer display screens. A CRT works by moving an electron beam back and forth across the back of the screen. Each time the beam makes a pass across the screen, it lights up phosphor dots on the inside of the glass tube, thereby illuminating the active portions of the screen. By drawing many such lines from the top to the bottom of the screen, it creates an entire screen-full of images.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

Output Devices

It refers to any machine capable of representing information from a computer. This includes display screens, printers, plotters, and synthesizers. Refer to Table 1 for a complete list.

b) Printer

Dot-Matrix Printer - a set of steel pins strike an inked ribbon onto paper producing any desired sequence of dots.
Ink-Jet Printer - fires a jet of liquid ink through tiny holes and it gives high resolution for almost professional quality, sharp printing.
Laser Printer - works like a photocopier, powdered ink is fused onto paper by heat and pressure. The sharpness of the print is considered to be of very high resolution and suitable if we require full professional printing quality.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

Some Common Storage Devices

Hard Drive

The hard drive is the primary device that a computer uses to store information. The hard drive stores programs, data files, saves files, and organizes files. The hard drive is located inside the computer case. The hard drive, magnetically stores data on stacks of rotating disks called platters.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

RAID -- Redundant Array of Inexpensive Disks

Removable Hard Disk

As users get more and more sophisticated, they develop applications; such as multimedia systems, that requires large memory size and fault tolerance to be built into the storage device. This is where the RAID technology comes in. The RAID technology is an affordable alternative to mass storage with a high throughput and reliability.

A RAID is simply and array of small disks together to obtain the performance of more expensive high end disks. It is based on the idea that disk throughput can be increased by having many disk drives with many heads operating in parallel. The distribution of data over multiple disks automatically forces access to several disks at one time improving throughput. Disk arrays can be used to store large amounts of data, have high I/O rates and take less power per megabyte (when compared to high end disks) due to their size.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

RAID -- Redundant Array of Inexpensive Disks

Optical Storage

Optical storage has been the most popular storage medium in the multimedia context due its compact size, high density recording, easy handling and low cost per MB. CD is the most common, while Laser disc and DVD are also popular.

DVD

A RAID is simply and array of small disks together to obtain the performance of more expensive high end disks. It is based on the idea that disk throughput can be increased by having many disk drives with many heads operating in parallel. The distribution of data over multiple disks automatically forces access to several disks at one time improving throughput. Disk arrays can be used to store large amounts of data, have high I/O rates and take less power per megabyte (when compared to high end disks) due to their size.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

RAID -- Redundant Array of Inexpensive Disks

Communication devices

When we use computers, we usually need to transfer data and information from one computer to another. The transmission of data from one location to another is done digitally, meaning that the data are translated into bits of ‘0’s and ‘1’s. Connectivity refers to the use of computer networks to link to people and resources. You can link or connect to large computers and the Internet providing access to world-wide information resources just by sitting in front of and clicking on your computer. On a larger, collective scale connectivity may refer to the internet bandwidth coming into and going out of a country, and the quality of the infrastructure within the country for linking to the internet.

To connect a computer to a network we need to use communication devices. These devices include: modem, network interface card, wireless network interface card, network access point transmitter and Modem, short for modulator-demodulator is an electronic device that converts a computer’s digital signals into specific frequencies to travel over telephone or cable television lines. At the destination, the receiving modem demodulates the frequencies back into digital data. Computers use modems to communicate with one another over a network.

1.2 Four kinds of computers – microcomputer, minicomputer, mainframe, and supercomputer

RAID -- Redundant Array of Inexpensive Disks

Communication devices

A network interface card, more commonly referred to as a NIC, is a device that allows computers to be joined together in a LAN, or local area network. Networked computers communicate with each other using a given protocol or agreed-upon language for transmitting data packets between the different machines, known as nodes. The network interface card acts as the liaison for the machine to both send and receive data on the LAN. The most common language or protocol for LANs is Ethernet. An Ethernet network interface card is installed in an available slot inside the computer. A network interface card does not have to be hard wired with physical cable. Wireless network interface card, such as the Wireless Ethernet cards are installed like their wired counterparts, but rather than a port for an Ethernet cable, the card features a small antenna. The card communicates with the central wireless switch or hub via radio waves. Wireless Internet access, sometimes referred to as a “hot spot,” is a local area network (LAN) run by radio waves rather than wires. Wireless Internet access is broadcast from the central hub which is a hard-wired device that actually brings in the Internet connection. The hub, located at the main computer system or server, broadcasts Internet connectivity to clients, which is basically anyone within “hearing” range who is equipped with a wireless LAN card.