A computer is a device which calculates and processes large amounts of data in different forms . It allows the users to quickly and automatically store and process information. A computer can edit text , create images, graphs, animate, translate language and even can make us play games . In other words, computer is a programmable machine designed to automatically and sequentially perform arithmetic and logical operations on the user’s input , and after processing gives the desired output.
A system is a set of components that work together to achieve a common goal. A computer system consists of three key components. Firstly, computer hardware that includes all the mechanical, electrical or electronic parts of computer components. The second component is computer software that Includes operating system, programs or application that instruct a computer how to process the data and generate the information required.
Thirdly, Computer personnel which include people who prepare data for computerised input write computer programmes, monitor computer operations and distribute the output. There are also end users who use computer resources.
Mainframe computers are mainly large size computers and very powerful multi-user computers that can support programs simultaneously. This computer may simultaneously execute different action or processes. A large number of users may use mainframe computers at the same time. An outsized organization may use mainframe computers to carry out large scale processes Such as processing payroll for the organization.
Another category of computer is mini-computers which are medium-sized multiprocessing computers. They can also perform many different actions simultaneously, and at the same time support many users. The distinction between minicomputers and tiny mainframes has recently become unclear. The distinction often depends on how the manufacturer wants to commercialize its machines. Organizations can use a mini-computer to manage information in a small financial system or to maintain a small database of registration or application information
Workstation is dominant, single-user and networked computers. They have the ability to store and process large volumes of data via big servers. Workstations are normally linked together to form a computer network called a local area network. Which means multiple people, such as office staff, can interconnect and share electronic files and data with each other.
Personal computers are also known as microcomputers and are a very popular computer category which is used by individuals. The personal computer is a comparatively low cost, small-sized computers designed for an individual user. Computers can be called desktop computers that remain on the desk, or laptop computers that are portable and lightweight. Organization and individual use personal computers for multiple tasks including word processing, accounting, desktop publishing, presentation preparation and delivery, spreadsheet organization and database management.
The characteristics of computers that are useful for users include speed, accuracy, diligence, versatility and storage capacity.
Speed: Computers work at high speed. A powerful computer is capable of performing about 3-4 million simple instructions per second.
Accuracy: Another feature of computer is its accurate functions. Errors that may occur can almost always be attributed to human error (inaccurate data, poorly designed system or faulty instructions/programs written by the programmer).
Diligence: Computers are highly reliable. They do not suffer from human traits of boredom and tiredness resulting in lack of concentration. Computers are better than human beings to perform huge and repetitive jobs.
Versatility: Computers are multipurpose machines and are capable of performing any task as long as it can be broken down into a series of logical steps.
In present scenario, computers can store large volumes of data. A piece of information once recorded (or stored) in the computer, can never be forgotten and can be retrieved almost instantaneously.
1. The computer accepts input:
The input of the computer is data in a computer system. Every person, for example, can provide the input by using a keyboard or by a computer or other devices like a diskette or a CD-ROM.
The computer conducts useful operations and manipulates the data in different ways. The processing is this manipulation. For example, calculations are made, words or numbers are sorted and the documents and images are altered according to user instructions and graphs are drawn. A computer processes data in the CPU.
The computer also has the function of storing data. A computer needs to store data so that it can be processed. Most computers have several data storage locations. The position of the data storage unit depends upon the usage of the data. The machine places the data at one location when they are waiting and at another position even when they aren’t required for processing instantly. Data storage on the computer is called “online storage,” while data storage on computer tapes, disk drives and CD-ROMs are known as “offline storage.”
The computer produces output. Computer output is information that has been produced by a computer. For examples reports, documents, music, graphs, and pictures. Output can be in several different formats, such as paper, diskette, or on-screen.
A computer system has four basic units that include input unit, storage unit, central processing unit and output unit. Central Processing unit that comprises of Arithmetic logic unit and control unit,
1. Input Unit: This unit is used for entering data and programs into the computer system by the user for processing. Storage Unit: The storage unit is used for storing data and instructions before and after processing.
Output Unit: The output unit is used for storing the result as output produced by the computer after processing.
Processing: It is called processing to carry out operations such as arithmetical and logical operations. The Central Processing Unit ( CPU) uses data and storage device instructions to execute calculations of all kinds on the basis of instructions and the sort of data provided. Then it is returned to the storage device.
Arithmetic Logic Unit: All calculations and comparisons are performed inside the ALU, based on the instructions provided. This carries out arithmetical activities such as adding, subtracting, multiplication, dividing and logical operations as larger, smaller and equivalent.
Control Unit: Control unit is used to control all operations, such as input, processing, and output. It performs all activities inside the computer step by step.
Another important part of computers is its memory which can be classified into two types; primary memory and secondary memory.
1. Primary Memory has two part, RAM and ROM
RAM or Random Access Memory is the unit in a computer system. It’s the place on a computer where you can momentarily keep the operating system, application programs and current data to be accessed by the processor of the computer. Its contents are only accessible while the machine is on. It’s unpredictable. If the computer has turned off, the output of RAM is no longer accessible.
ROM or Read Only Memory is typical memory which can only be read and contents of which are not lost even when the computer is switched off. It typically contains the manufacturer’s instructions. ROM also stores an initial program called the ‘bootstrap loader’ whose function is to start the operation of the computer system once the power is turned on.
2. Secondary Memory:
RAM is a volatile storage capacity that has limited capacity. Auxiliary / secondary memory is other than RAM storage. These involve outermost, linked and managed devices that enable the continuously storing of programs and data. The magnetic and optical secondary storage devices are two types. Like hard disks and optical disk units, magnetic disks are CDs and DVDs.
Hard drives are made of rigid material and usually consist of a pile of metal disks screened in a box. They may be rewritten.
Peripheral devices: Peripheral devices are connected to the computer externally. These devices are used for performing some specific functions.
Peripheral devices are as follows:
These devices are used for storing or processing data and instructions on a computer, and for supplying the processed data to a user. Input / output devices for users to speak with the computer are important. It can be said that input devices bring information into the computer and output devices get information out of a computer system.
These input/output devices are also called peripherals since they surround the CPU and memory of a computer system.
1. Input Devices: An input device is any device that gives input to a computer. There are many input devices which are connected to the computer such as:
Most common devices are keyboard and mouse. Every key, users press on the keyboard and every movement or click, they make with the mouse sends a specific input signal to the computer.
I. Keyboard: The keyboard is a standard typewriter keyboard with a few additional keys. The basic QWERTY layout of characters is maintained to use the system easily. The additional keys are included to perform certain special functions. These are known as function keys that vary in number from keyboard to keyboard.
II. Mouse: This device controls the movement of the cursor or pointer on a display screen. A mouse is a small object which user can roll along a hard and flat surface. As users move the mouse, the pointer on the display screen moves in the same direction.
III. Microphone: Microphone is an input device, which takes voice as input. The voice communication is more error-prone than information through keyboard.
IV. Optical Scanner: These devices are used for automatic data collection. Such devices completely eliminate manual input of data.
V. Touch Screen: Touch panel displays and pads are now being offered as alternatives to keyboard.
2. Output Devices: Output device obtains information from the CPU and presents it to the user in the preferred from. The processed data, stored in the memory of the computer is sent to the output unit, which then converts it into a form that can be understood by the user. The output is typically produced in one of the two ways: on the display device, or on paper (hard copy).
I. Monitor: It’s frequently used with “computer display” or “computer screen.” Monitor ‘s output is similar. It may show information through Cathode Ray Tube ( CRT) or LCD. The monitor is attached to a keyboard for manual character input and shows the details when the character is entered. The software or task output may also be shown. Different sizes of monitors are available.
II. Printers are used to produce paper output in the form of hard copy. They can be categorised as Impact or Non-impact printers Based on the technology.
Computer software is the set of programs that makes the hardware execute a set of tasks in specific order. Hardware and software are complimentary to each other. Both have to work together to produce significant results. Computer software is categorised into two major categories that include system software and application software.
I. System Software: System software comprises of a group of programs that control the operations of a computer equipment including functions such as managing memory, managing peripherals, loading, storing. An operating system is a part of system software that provides an interface for a user to communicate with the computer, manages hardware devices, manages and maintains disk file systems and supports application programs. Some examples are MS DOS (Microsoft’s Disk Operating System), UNIX.
It is established that an operating system is a software constituent of a computer system that is responsible for the management of several activities of the computer and the sharing of computer resources. It hordes several applications that run on a computer and manages the operations of computer hardware. Users and application programs access the services offered by the operating systems, through system calls and application programming interfaces. Users interact with a computer operating system through Command Line Interfaces (CLIs) or Graphical User Interfaces known as GUIs. Briefly, it can be said that an operating system allows user to interact with computer systems by acting as an interface between users or application programs and the computer hardware. Common operating systems are LINUX, Windows.
II. Application software: This type of Software perform a specific task for the user, such as word processing, accounting, budgeting or payroll. Word processors, spreadsheets, database management systems are all examples of general purpose application software. There are several types of application software such as word processing software, database software, spreadsheet software, presentation software and multimedia software.
The most popular application software is word processing. With the support of a typewriter, the key benefit of word processing being that the consumer can alter the entire text without retyping. Word processors can manipulate documents and format them.
Spreadsheets are computer programs that allow users to electronically create and manipulate spreadsheets (tables of values arranged in rows and columns with predefined relationships to each other). Spreadsheets are used for mathematical calculations such as accounts, budgets, and statistics.
Database management applications are computer programs that permit users to create and manipulate data in a database. A database is a collection of related information that can be manipulated and used to sort information, conduct statistical analyses or generate reports.
Printing packages and graphics are computer programs which encourage the creation of sophisticated images for slide presentations and reports by operators. You can also produce different kinds of charts and graphs. Many software applications include: paint programs, desktop publishing applications, etc.
Communications applications normally include software to allow operators to send emails and dial into other computers.
Computer language: Computer language or programming language is a coded syntax used by computer programmers to interconnect with a computer. Computer language establishes a flow of communication between software programs. The language facilitates a computer user to dictate what commands the computer must perform to process data. These languages can be categorized into following groups.
1. Machine language: It is a basic type of computer language, which was developed initially. It is dependent on the machine. A program written in machine language cannot be run on another type of computer without significant alterations. Machine language is also called as the binary language i.e. the language of 0 and 1 where 0 stands for the absence of electric pulse and 1 stands for the presence of an electric pulse. The main benefit of this language is that it makes fast and efficient use of the computer. It requires no translator to translate the code.
I. All operation codes have to be remembered.
II. All memory addresses have to be remembered.
III. It is hard to amend or find errors in a program written In the machine language.
IV. These languages are machine dependent i.e. a particular Machine language can be used on only one type of compute.
2. Assembly language: Machine language disadvantages have been developed to overcome. This is a low level but a very important language in which operating codes and operands are displayed instead of 0’s and l’s as alphanumeric symbols. The alphanumeric symbols are known as mnemonic codes and can be combined with up to 5 letters. Compared to computer language, this language is simpler to learn and use. Finding and rectifying errors is easy and easy.
3. High level language: High level computer languages give formats close to English language and the intent of developing high level languages is to facilitate user to write programs effortlessly and in their own native language environment (English). High-level languages are fundamentally symbolic languages that use English words and/or mathematical symbols rather than mnemonic codes. Each instruction in the high level language is translated into many machine language instructions thus showing one-to-many translation.
Computer Viruses: A computer virus is a self procreating program that can be messaged or replicated in other programs or documents. Most viruses or worms are malicious programs designed to pollute and control an owner ‘s computer. When computer viruses are allowed, they spread via a computer system or network. This means that the virus file can not be opened or executed to give life to the virus. Such viruses search for other programs to attack after it is disabled. Both viruses tend to function well, so this is the primary reason why they multiply well in the programs they find.
Types of computer viruses: First is Trojan Horse. A program was written to deliver a malicious program that may then cause destruction to the computer. A Trojan horse is delivered by someone or concealed within another program that may seem harmless. Another virus is Spyware a program written to monitor your actions on a computer. A most common category of spyware is a key-logger program. This program can record every keystroke and mouse click you make. Spyware can be delivered via a Trojan horse program. Adware is a type of malware. Adware is designed to pop up advertisements. Adware can be very irritating. Worms cause sluggishness in a network. A worm will replicate itself and spread from computer to computer. Worms are usually spread through email attachments.
Users must install following to protect his computer from viruses and malwares.
To summarise, computers are an effective tool that makes data meaningful. In today’s complex world, computers are the essential requirement for people to perform daily tasks. Computers are used to store, capture, process and transfer data through operators and men. The workloads which would be excreted on them can not be coped with. High speed, precision, diligence, versatility and storage are the main features of a computer.