Characteristics of Computer

CHARACTERISTICS OF A COMPUTER

 • Speed: The computer can manipulate large data at incredible speed and response time can be very fast.

 • Accuracy: Its accuracy is very high and its consistency can be relied upon. Errors in computing are mostly due to human rather than technological weakness. There is in-built error detecting schemes in the computer.

 • Storage: It has both internal and external storage facilities for holding data and instructions. This capacity varies from one machine to the other. Memories are built up in K (Kilo) modules where K=1024 memory locations.

 • Automatic: Once a program is in the computer‟s memory, it can run automatically each time it is opened. The individual has little or no instruction to give again.

 • Reliability: Being a machine, a computer does not suffer human traits of tiredness and lack of concentration. It will perform the last job with the same speed and accuracy as the first job every time even if ten million jobs are involved.

 • Flexibility: It can perform any type of task once it can be reduced to logical steps. Modern computers can be used to perform a variety of functions like on-line processing, multi-programming, real time processing e.t.c.

 CLASSES OF COMPUTER

 • Analog Computers: This class of computer are special purpose machines that surfaced in the late forties (1948). They are used solving scientific and mathematical equations or problems. An example is the thermal analyzer. Data and figures are represented by physical quantities such as angular positions and voltage.

 • Digital Computers: They are machines made up of combinations of chips, flip-flops, buttons and other electronic devices to make them function at a very fast speed. A digital computer has its numbers, data letters or other symbols represented in digital format. They are mostly special purpose machines unless minor specifications are included in the design. • A computer that combines the features of a digital and analog computer is called a hybrid computer.

 TYPES OF COMPUTER

 Super Computers • A super computer is the most powerful computer available at any given time. These machines are built to process huge amounts of information and do so very quickly. • Supercomputers are built specifically for researchers or scientists working on projects that demand very huge amounts of data variables; an example is in nuclear research, where scientists want to know exactly what will happen during every millisecond of a nuclear chain reaction. (To demonstrate the capability of super computers, for an air pollution control project that involves more than 500,000 variables, it will take a mini 9 computer about 45 hours to complete the simulation process while it will take a super computer 30 minutes only). • They are big in size, generate a lot of heat and are very expensive. (Super computers are made by CRAY Company). 

Mainframe Computers • The largest types of computers in common use are the mainframe computers. They are designed to handle tremendous amounts of input, output and storage. • They are used mainly by large organization like the PHCN, NITEL, and CBN. • Other users access mainframe computers through terminals. Terminals consist of a type of keyboard and a video display i.e. monitors. The mainframe is usually in the computer room (Mainframe computers are made by IBM, Boroughs & Univac). Mini Computers • These are physically small compared to mainframes and are generally used for special purposes or small-scale general purposes. • The best way to explain the capabilities of mini computers is to say they lie between mainframes and personal computers. Like mainframes, they can handle a great deal more input and output than personal computers. • Although some minicomputers are designed for a single user, many can handle dozens or even hundreds of terminals. • Advances in circuitry means modern mini computers can out-perform older mainframes of the 60s. (Examples are Digital Equipment Company‟s PDP II and Vax rang) Workstations • Between mini computers and micro computers – in terms of processing power is a class of computers known as workstations. • A workstation looks like a personal computer and is typically used by one person, although it is still more powerful than the average personal computer. • The differences in the capabilities of these types of machines are growing smaller. They significantly differ from micro computers in two ways: the 10 central processing unit (CPU) of workstations are designed differently to enable faster processing of instructions and most of the micro computers can run any of the four major operating systems. • Workstations [(Reduced Instruction Set Computing (RISC)] use UNIX operating system or a variation of it. (A note of caution: Many people use the term workstation to refer to any computer or terminal that is connected to another computer. Although this usage was once a common meaning of the term, it has become out dated) (The biggest manufacturers of workstations are Sun Microsystems). Micro Computers/Personal Computers • The term microcomputers and personal computers are used interchangeably to mean the small free- standing computers that are commonly found in offices, homes and classrooms. • Many micro computers are built specially to be used in watches, clocks, and cameras. Today, PCs are seriously challenging mainframes and mini computers in many areas. In fact today PCs are more powerful than mainframes of just a few years ago, and competition is producing smaller, faster models every year. 

TYPES OF PERSONAL COMPUTERS

 • THE DESKTOP: This is the first type of PCs and the most common. Most desktops are small enough to fit on a desk, but are a little too big to carry around

. • THE LAPTOP: They weigh about 10pounds (4.5kg). They are battery – operated computers with built–in screens. They are designed to be carried and used in locations without electricity. Laptops typically have an almost full –sized keyboard. 

• THE NOTEBOOK: They are similar to laptops and PCs, but smaller. They weigh about 6 to7 pounds (2.7 – 3.2kg). As the name implies, they are approximately the size of a notebook and can easily fit inside a brief case.

 • THE PALMTOP: They are also known as personal digital assistance (PDAs) and are the smallest of portable computers. Palmtops are much less powerful than notebooks or desktops models and feature built-in 11 applications such as word processing. They are mostly used to display important telephone numbers and addresses.

 FUNCTIONS OF PERSONAL COMPUTERS

 Personal computers can do a lot of things. The most common tasks computers perform include: • Writing documents such as memos, letters, reports and briefs • Budgeting and performing accounting tasks • Analyzing numeric information • Searching through lists or reports for specific information • Scheduling and planning projects. • Creating illustrations • Communicating by using electronic mail • Advertising products and services.

 COMPONENTS OF A PERSONAL COMPUTER 

A personal computer is not a single unit. A typical computer consists of several basic parts or components that work together. To perform any computer task you need two major components: the hardware and the software. [1]The hardware is the physical components of a computer system. Generally you can think of the hardware as any part of the computer that you can see or touch. Although the hardware of a computer is capable of performing marvelous tasks, it cannot accomplish any of them without the vital instructions that the software provides. [2]The software is a set of instructions that tells the hardware what to do. You can‟t see or touch the software, although you can see packages that contain the software. It is typically distributed on CD-ROM disc and is installed on the computer hard drive.

 HARDWARE COMPOINENTS

 The major hardware components of the personal computer consist of the following: 

[1]Input Devices: Input devices are the computer hardware that accepts data and instructions from a user. Input devices have been built in many forms to help in communicating with the computer. The most common input devices are the keyboard and the mouse.  

The Keyboard: The keyboard of the personal computer comes in a number of styles. The various models may differ in size and shape, but except for a few special purpose keys, MDS keyboards are laid out almost identifiably. The most common keyboard used today was established by IBM. The computer keyboard is more than just a typewriter. It contains all of the keys required for typing letters, numbers, plus the keys for entering commands and moving around on the screen. There are 101 keys arranged in groups: Alphanumeric, Numeric, Function and Arrow/Cursor movement keys, and Computer keys.

 ii. A mouse is a pointing device that enables you to quickly move around on the screen, and to select commands from menus rather than type the commands. A mouse is useful because it enables the user to point at items on the screen and clicks a button to select the item. It is convenient for entering certain data. iii. Track Balls: A trackball is an input device that works like an upside-down mouse. You rest your hand on the exposed ball and the fingers on the button. To move the cursor around the screen, you roll the ball with your thumb. Trackballs are much popular with notebook computers. They require less desk space than the mouse. iv. The Joystick: This is a pointing device commonly used for games. It is not used for business applications. v. The Pen: It is an input device that allows a user to write on or point at a special pad on the screen of a pen-based computer, such as a personal digital assistant (PDAS). vi. The Touch Screen: A computer screen that accepts input directly into the monitor; users touch electronic buttons displayed on the screen. It is appropriate in environment where dirt or weather would render keyboards and pointing devices useless. vii. The Scanner: This is an input device used to copy images into a computer memory without manual keying. It works by converting any image into electronic form by shinning light on the image and sensing the intensity of reflection at every point. There are several kinds of scanners. These includes: hand held, flatbed, and sheetfeds. 13 viii. The Bar-Code Reader: This is one of the most commonly used input devices after the keyboard and mouse. It is commonly found in supermarkets and department stores. This device converts a pattern of printed bars on products into a product number by emitting a beam of light frequently from a laser that reflects off the bar code image. A light sensitive detector identifies the bar-code image by special bars at both ends of the image. Once it has identified the barcode, it converts the individual bar patterns into numeric digits