Introduction to Computer

What is Computer?

àComputer is an electronic device, in which we can insert data process it to generate result in the form of information, which is useful to us.

Computer is derived from the Latin word ‘Computare’ which means ‘Calculate’.

Some advantages and Disadvantages of computer:

Advantages:

1. Speed: Speed of computer is very fast, it process data in the form of electronic pulses. So, it can process data in fraction of seconds.

2. Vast Storage: Storage capacity of computer is very vast, it can hold/store huge data in a small place in a disk.   

3. Versatility: Computer is having capacity to process multiple types of data like characters, voice, images/picture, symbols, numbers etc.   

4. Diligent: Computer can work or could perform task without tiredness and very consciously without making mistakes.

5. Accuracy: Computer can process data very correctly without making any mistake, if user makes mistake then only computer gives wrong out put else it gives accurate result.

6. Reliability: We can depend on output given by the computer since it generates accurate result without any mistake. Even if any mistake it can correct some errors itself by the computer.

Disadvantages:

1. Dull Machine: Computer is a dull machine it cannot think itself, man makes it intelligent by writing program for it. 

2. Cost:  It is an expensive machine, its cost is high and it consumes electricity to operate it.

3. Physical causes: It causes some physical effect when we will use it continuously for long time, like causes backache, eyesights etc.   

4. Size: It requires space to keep the computer in your office or house because it is large in size like desktop computer requires tables chairs etc. to keep set of computer. 

5. Data loss: There are a lot of changes to loss data in computer due to the failure of disk.    

Computer system

It consists of three major categories:

1.     Hardware

2.     Software

3.     Personnel/User =Person who can operate computer.

The Hardware:

The physical components of a computer or parts of a computer, which we can touch and feel, are called Hardware.

àHardware consists of three basic units:

1. Input units     2. Processing/Storage units   3. Output units         

1. Input unit:

This is the unit through which we can insert data and instructions into the computer. e.g. of Input unit devices are:

Keyboard, Mouse, Scanner, Joystick, Trackball, Lightpen, MICR, OCR, BCR etc

1.1. Keyboard: It is an input device .It is also called primary input device of the computer .By the help of keyboard we can insert data like: Alphabets, Numbers, Symbols etc.

1.2. Mouse: It is a pointing input device, by the help of mouse, we can point on any object of GUI (Graphical User Interface System) and we can perform click, double click or right click action to give data and instructions to the computer.

1.3. Scanner: It is an input device, through which we can scan & insert images or pictures, photos & graphics texts photocopy into a computer. It is just like a photocopy.

1.4. Joystick: Like mouse, a joystick is also a pointing device. It is used to move the cursor position on the screen .A joystick has a stick with two ball one its lower and another its upper end and buttons mounted on the stick or elsewhere on the joystick can be pressed to execute commands. Joystick is mainly useful to play games.

1.5. Trackball: Trackball is also a pointing device and contain a ball on the upper part of it. The ball can be rotate to move cursor in any direction on the screen .It be mostly used on laptop computer where there is no space for conventional mouse.

1.6. OCR (Optical Character Reader): OCR is an input device, which is used to read text from paper and translates the images into a form that the computer can manipulate .An OCR Reader scans data (Character) in the form of images or photos and converts it electronic signals. It is widely used in Airline, Bank, Postal office (for reading postal codes) etc.

1.7. BCR (Bar Code Reader): BCR is an input device, which can read Bar codes of any product and converts them into electrical pulses, which can be processed by a computer. Bar codes are called Universal Product Code (UPC) and. They are used on mostly grocery items. BCR is     useful to the supplier, manufacturers, supermarkets etc.

1.8. MICR (Magnetic-Ink character Reader): MICR is an input device, which is capable of reading character on a paper written with magnetic ink. It is widely used by banks to process large volumes of chouse and deposit forms written everyday.

Special ink called magnetic ink (i.e. an ink which contains iron oxide particles) is used to write characters on the chouse and deposit forms.

1.9. Light Pen: A pencil shaped devices used to select position by detecting the light coming from points on screen is light pen. They are very sensitive to the short burst of light emitted from the phosphor coating at the instant the electron beam strikes on particular point .An activated light pen, pointed at a spot on the screen and generates an electrical pulses that causes the co-ordinate position of the electron beams to be recorded.

3.  Processing and Storage Units:

C  Example of Processor And Storage Devices: CPU (Central Processing Unit), Memory and Disk.

i)       CPU (Central Processing Unit): This is a main part of a computer. A man could not live without heart like wise computer can not process any actions without CPU, so we can say CPU is a heart of a computer, it can not alive without it. This main Part of a computer is having three more parts/components into it these are:

a)     MU (Memory Unit): This part of a CPU is having capacity to hold data temporarily while processing the data/instructions. It holds/stores data or instructions into it before actual going into processing part.

b)    ALU (Arithmetic and Logic Unit): This part of a CPU is an actual processing part of the CPU. This part of CPU performs two operations: Arithmetic calculations and Logical comparisons on data and generates information.

c)     CU (Control Unit): This part of a CPU act as an input and output controller. It controls from what type of input devices data is coming and on what type of output devices data has to be send.

Storage Devices

The computer devices that store the data permanently for future use or temporarily for recent use. The memory & storage devices are given below 

 

Memory

Memories are the electronic holding place for instructions and data for Microprocessor addresses quickly.

There are two types of memory:

1. Primary Memory

This memory is an immediate use of memory it requires to store data temporarily.

Primary memory is storage units of the computer where it can store or remember current data and instructions or program remain resident in memory which are executed in computer.

So, when computer is to process a program, instruction and associated data should be immediately available, Computer requires inter memory not only storage program and data but storing result also, which can be there after transferred to output unit. Large number of basic units called memory cells forms it. The cell is a device or electronic circuit that is capable to store binary digit or bit.

Types of Primary Memory:

1.1  RAM (Random Access Memory)

The kind of memory used for holding programs and data being executed is called random access memory (RAM). The RAM can be both read and write. It is volatile memory, the contents of RAM are lost when power is turn off. There are two types of RAM

i.                    SRAM (Static Random Access Memory)

ii.                  DRAM (Dynamic Random Access Memory)

1.2 ROM (Read Only Memory)

The ROM is a non-volatile memory. It is used to store basic set of instructions called the BIOS (Basic Input-Output System) or Firmware (Program fixed by manufacturer).  A computer needs to run when it is first turned on. This is a permanently stored on computer chip in the form of electronic circuits. There are three types of ROM:

i.                    PROM (Programmable Read Only Memory)

ii.                  EPROM (Electrically Programmable Read Only Memory)

iii.                EEPROM (Electrically Erasable Programmable Read Only Memory)

2. Auxiliary or Secondary Memory

This memory is necessary to store data for the future use permanently. In this memory we can read, write and modify data any time as per our requirement these are also known as storage devices.

These are two types: 1. Internal =which is Fixed inside computer e.g. Hard Disk.

2. External =which can be used externally (from the outside) of the computer e.g. Floppy disk, CD, Zip disk, Pen drive etc.   

The storage devices can be classified as either magnetic or optical or a combination called magneto-optical. Magnetic storage devices used magnetic materials and magnetism mechanism for reading & writing. The optical storage devices use to store and retrieve information from fiber optics disk. The auxiliary memory is also known as secondary memory or backup storage. It is the media for mass storage information.

Magnetic Media: They are having magnetic medium to store/hold electronic data in it. E.g.

i.                    Hard disk

ii.                  Floppy disk

iii.                Magnetic Tape Unit

iv.               Zip Disk

i. Hard Disk

The hard Disk is an internal disk, which is fixed inside computer cabinet where in the operating system, all data and program files are stored. When user switches on the computer, the operating system is automatically loaded into memory form hard disk making the computer system operational.

This disk is a main or primary storage device of a computer. It is made of the metallic things, as name suggested it is hard and very safety than other storage devices. It resides inside computer, so it is called non-removable disk or Internal Disk.

ii. Floppy Disk

The floppy disk is one of the most commonly used storage media can be content and easily managed. The floppy is made of flexible plastic material. These were developed to replace cassette tape as data storage medium for use with microcomputer. The disk is enclosed in a protective jacket of plastic with a soft material. Capacity of this drive is 1.44 MB.

iii. Magnetic Tape

Magnetic tapes are used in computer mainly as external devices. They are known as sequential storage device, which provides serial or sequential access. The tape used in the computer can be 12.5 mm to 25 mm wide plastic film type and 500 to 1200 meters in length. The speed of data transfer is 15000 to 35000 CPS (Character per Second). They are mainly useful for backup storage.

iv. Zip Disk

The Zip Disks are slightly larger than the floppy disks, and are about twice as thick. They can hold 100 MB of data. They are relatively inexpensive and durable; they have become a popular media for backing up hard disk and for transporting large files.

Optical Media: In Optical storage devices, light beam is used to read/write data in it. E.g.

i.                    CD-ROM (Compact Disk Read Only Memory)

ii.                  DVD-ROM (Digital Versatile/Video Disk Read Only Memory)

i. CD-ROM (Compact Disk Read Only Memory):-

The CD is also storage device. It can store up to 700 MB of data. It is read only memory type, which only can be used to read but cannot be modify. Now a days’ Re-writable CD are also available. You can remove old data and can add new data.

It also made of a fiber optic material and having magnetic coating on the surface, so this magnetic coating can capture data into it. To write data into it, it requires "CD Writer Device" and to read data from it, it requires "CD ROM Drive” even data can be read from "CD Writer Device" but it is not practicable in some reason.

ii. DVD-ROM (Digital Versatile/Video Disk Read Only Memory):-

DVD-ROM looks like a normal CD-ROM but it has comparatively higher storage capacity and higher speed of accessing. A single DVD-ROM can hold minimum of 4.7 GB of data and maximum of 17 GB. It requires DVD Driver to read data from it and DVD Writer to write data into it. Now a days' Combo Drive Device available to read/write CD-ROM as well as DVD-ROM.

Memory Measurement

The small unit for the memory measurement is bit.

0 or 1                              1        Bit

4 Bits                              1        Nibble (Quad Bit)

8 Bits                              1        Byte (Octet) (A character)

1024 Bytes                      1        Kilo Byte (KB)

1024 KB                         1        Mega Byte (MB)

1024 MB                        1        Giga Byte (GB)

1024 GB                         1        Tera Byte (TB)

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3. Output unit:

Output unit or devices are those devices on which computer can display or send information for the users.

E.g. of output unit devices are: Monitor, printers, Graph plotter, Speaker etc.

3.1. Monitor: Monitor is a soft copy output device which users can view data or information directly on the screen .It looks like a TV screen. Monitor also called VDU (Visual display unit)

à Softcopy: Softcopy is a digital data or information stored in the form of electric pulses, which is stored in the disk and can be view on the screen.

à Monitor can be classified into two categories:

1. Black & White (Size: 12 inches)

2. Colored (Size: 14,15,17,21,24 inch etc)

1. Black & White Monitors are two types:

i. Monochrome ii. Mono VGA

i. Monochrome: Cannot display graphics.

ii. Mono VGA (Visual Graphic Adaptor): It can display Graphical /picture mode output.

2. Coloured Monitor can display graphical/picture mode display in colour. Colour monitors are categories into different mode of display as per the display adaptors:

i. VGA   ii. SVGA   iii. CGA   IV. MCGA v. EGA

=> VGA=Visual Graphic Adaptor.

=> SVGA=Super Visual Graphic Adaptor

=> CGA=Coloured Graphic Adaptor

=> MCGA= Multi coloured Graphic Adaptor (Array)

=> EGA=Enhanced Graphic Adaptor (Array)

3.2 Printer: Printer is a hard copy output device, on which computer can send output to print matters on paper.

Hardcopy: printed matters or output on the papers is called Hard copy.

Types of Printer:                  

                                                                                            

Impact printers: Impact printers use electromechanical mechanism that causes hammers or pins to strike against a ribbon and paper to print the text.

Non-Impact printers: This type of printers does not use technology like an impact printer. Non –Impact printers use thermal, Chemical electrostatic, laser beam or ink –jet technology for printing. These printers are faster than impact printers.

àExample of Impact printers: 1. Dot-matrix printer. 2. Line printers

3. Daisy Wheel printers etc.

àExample of Non- Impact printer: 1.Ink-jet printers

2.Bubble jet printers 3.Laser printers etc.

3.3. Plotter: Plotter is another hard copy output device, which is useful to print large sheet of drawing on the large paper. Large drawing means computerized drawing designed by an engineer in CAD (Computer Aided Design).

3.4. Speaker: Speaker is a voice output device, it gives output like sound/voice type of data OR we can play sound in computer.

Types of software and programming language

 Software:

 => Software is a logical component of the computer. It is a collection of programs to enter data or instructions into computer. Software is an interface for user to interact with computer. Program is a set of instructions/Commands to get a specific task done.

All the hardware will be lifeless without software because without software we cannot use hardware.

So, we can say software is a soul of computer and hardware is a body of a computer.

Types of software:

1.                 Application Software

2.                 System Software

3.                 Utilities Software

2.1 Application software: -

1. General Purpose Software

          2. Specific Purpose Software

2.1.1. General Purpose: It is software, which is designed for the General purpose. That means everyone can use it generally like official work as well as personal work. Few examples of such type of software are: Ms-Word, Ms-Excel, Ms-PowerPoint, Adobe PageMaker, and Adobe PhotoShop etc.

2.1.2. Specific Purpose:

It is designed to do certain specific tasks. These are supplied by the software companies or software vendor and computer manufacturers. Few examples of such type of software are: Accounting, Inventory Management, Payroll, Statistical analysis, Personal management, processing and printing SLC result, maintaining school MIS etc.

2.2 System software: -

          1. Operating System

          2. Programming Language or Language Processor

2.2.1. Operating System: It is system software, which allows us to operate whole computer system. OS allows the user to communicate with the hardware or it establishes the communication between user and machine. All the resources related to the computer system are managed by it.

2.2.2. Programming Language: It is group of programs or language software in which we can write set of instructions to make a program. As we know that the computer being an electronic machine understands only 0s and 1s. So it needs a set of instruction in the language, which it understands to perform the specific tasks. Programming language is a language that communicates with the computer. It is a set of code that the programmer writes to instruct the computer hardware to perform specified tasks.

Types of programming languages:

1. Machine level language:  This is the language of CPU i.e. the lowest level language. It is composed of 0’s and 1’s. It is easy for the computer to understand and it is also known as Machine oriented or Machine dependent because code written for one type of CPU cannot run on other type of CPU. To write code in this language programmer must have knowledge about hardware components.

Advantages

Fast operation

Easily understand by the computer.

Disadvantages

Difficult for the programmer to learn

Program becomes very lengthy

Hard to debug

Machine dependent

2. Assembly languages:

It is introduced in order to overcome the difficulty associated with the machine level languages. It is low-level language that permits the use of mnemonics (alphabetic code). Program written in assembly language must be translated into machine understandable form. Assembler does all these function.

Advantages:

Simple to understand and use

Less time is required to write the program

Program debugging is easier

Disadvantages

Machine dependent

Too difficult to understand for the first time

Slower than the machine level language

3. High level language (HLL):

High Level Languages are languages whose instructions are closer to English and mathematical notation. HLL must be translated into machine level during program execution. Translation is done by a program called compiler or interpreter.

Language Processors/Translators: It translates the set of instruction written by the programmers in programming languages into the machine understandable code (machine code).

          In the early days, the entire program has been written in the machine level languages but now various programming languages are used, which is quite easy to understand. At the time of execution these all languages must be translated into machine level languages. This is done by the translators.

Source program: A program originally written by the programmer in a language other than machine code.

Object program: When instructions are translated into machine code they are known as object code. If a complete program is translated into machine code and stored, is called object program.

Examples of language processors/Translators are as follows.

Assembler: translates low-level language into machine level.

Compilers: translates high-level program into machine level.

Interpreters: analyzes and executes the high-level source program one instruction at a time without producing object code.

4th GL (Generation Language)

As there is an increment of the relational databases, which make a new system known as fourth generation language, because they are considered to work at a higher level than normal high-level languages such as C, Pascal, COBOL etc. But now they are 3rd GL. Now days 4th GL are all part of application packages.

Features of 4th GL:

Define data

Define what processing must be done on the data

Define the output format

Define input data

Select combinations of standard processing operations

Handles users queries