Free Study Material of Information & Communication Technology
for CBSE UGC NET Paper I
Computer: A computer is a truly amazing machine that performs a specified sequence of operations as per the set of instructions (known as programs) given on a set of data (input) to generate desired information (output ).
A complete computer system consists of four parts:
- Hardware: Hardware represents the physical and tangible components of the
- Software: Software is a set of electronic instructions consisting of complex codes (Programs) that make the computer perform
- User: The computer operators are known as
- Data: Consists of raw facts, which the computer stores and reads in the form of
Functionalities of a computer
Any digital computer carries out five functions in gross terms:
- Takes data as input.
- Stores the data/instructions in its memory and use them when required.
- Processes the data and converts it into useful information.
- Generates the output
- Controls all the above four steps.
The following features characterize this electronic machine:
|ü Speed||ü Flexibility|
|ü Accuracy||ü Low cost|
|ü Storage and Retrieval
|ü Repeated Processing Capabilities
Applications of Computer
Following list are various applications of computers in today’s arena.
Following are the main five generations of computers:
|S. No.||Generation & Description|
|1||First Generation (1946-1959) – Vacuum tube based|
|2||Second Generation (1959-1965) – Transistor based|
|3||Third Generation (1965-1971) – Integrated Circuit based|
|4||Fourth Generation (1971-1980) – VLSI microprocessor based|
|5||Fifth Generation (1980-onwards) – ULSI microprocessor based|
Computer hardware consists of the following components:
- CPU (Central Processing Unit): CPU is considered as the brain of the computer. It performs all types of data processing operations, stores data, intermediate results and instructions (program).It controls the operation of all parts of
Fig: The relationship between different hardware Components
[A] CPU itself has following three components:
- ALU (Arithmetic Logic Unit): When the control unit encounters an instruction that involves mathematical calculation or decision/logic, it passes the control to the second component, i.e., the arithmetic logic unit (ALU). The ALU includes a group of registers – memory locations built directly into the CPU – that are used to hold data that are being processed by the current
- Registers: The register is the smallest high-speed storage area in the CPU. All data must be represented in a register before it can be
- Control Unit: This unit controls the operations of all parts of computer but does not carry out any actual data processing operations
[B] Primary memory consists of mainly two types of memories:
1. Random Access Memory (RAM): RAM is the internal memory of the CPU for storing data, program and program result. It is read/write memory which stores data until the machine is working. As soon as the machine is switched off, data is erased.
RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence a backup uninterruptible power system (UPS) is often used with computers. RAM is small, both in terms of its physical size and in the amount of data it can hold.
There are mainly three types of RAM available:
- Dynamic Random Access Memory (DRAM): A type of physical memory used in most personal computers. The term dynamic indicates that the memory must be constantly refreshed2 (reenergized) or it loses its contents. This type of memory is more
- Static Random Access Memory (SRAM): A type of memory that is faster and less volatile than DRAM, but requires more power and is more expensive. The term static is derived from the fact that it does not need to be refreshed like
- Synchronous Dynamic Random Access Memory (SDRAM): A type of DRAM that can run at much higher clock
2. Read Only Memory (ROM): The memory from which we can only read but can not write on it . This type of memory is non-volatile. The information is stored permanently in such memories during manufacture. A ROM, stores such instructions that are required to start a computer. This operation is referred to as bootstrap.
There are mainly three types of ROM available:
- MROM (Masked ROM): The very first ROMs were hard-wired devices that contained a pre-programmed set of data or instructions. These kinds of ROMs are known as masked ROMs which are
- EPROM (Erasable and Programmable Read Only Memory): The EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an EPROM eraser achieves this
- EEPROM (Electrically Erasable and Programmable Read Only Memory): The EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten thousand times. Both erasing and programming take about 4 to 10 ms (milli second).
A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in a computer where data is to be processed and instructions required for processing are stored. The memory is divided into a large number of small parts called cells. Each location or cell has a unique address which varies from zero to memory size minus one.
Memory is primarily of three types –
- Cache Memory: It is a very high-speed semiconductor memory which can speed up CPU. It acts as a buffer between the CPU and main memory.
- Primary Memory/Main Memory: Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data is lost when power is switched off.
- Secondary Memory: This type of memory is also known as external memory or non-volatile. It is slower than main memory. These are used for storing data/Information permanently.
1. Secondary Storage (External Storage Devices): Floppy diskettes, hard disk, tapes and optical disks come under the category of external storage devices or ancillary storage devices. These devices are very sensitive to environmental conditions (humidity and temperature) as well as to external magnetic fields and need to be stored.
- Floppy Disk: Floppy disks are primarily used on PCs. Information on a floppy disk is recorded in the magnetized states of particles of iron oxides evenly placed upon concentric circles known as Tracks.
- Hard Disk: It is a non-removable enclosed magnetic disk included in most PCs. It contains a stack of metal platters, each coated with iron oxide, that spin on a spindle and the entire unit is encased in a sealed chamber.
- Magnetic Tape: This is plastic tape, usually made of Mylar that is coated with iron oxide, thereby enabling the introduction (writing); retention (memory) and reading of magnetically recorded information. The best use of tape storage is for data that you do not use very often.
2. Peripherals: Peripheral devices are devices connected to the computer externally. If a peripheral device is disconnected, the computer will still be able to work; only functions performed by this peripheral device will not be available.
Mainly there are following types of peripheral devices:
A. Input Devices (How to tell it what to do): This unit makes a link between user and computer. The input devices translate the information into the form understandable by
- Keyboard- The most common and very popular input device which helps in inputting data to the computer.
- Mouse- Mouse is the most popular pointing device and cursor-control device having a small palm size box with a round ball at its base which senses the movement of mouse and sends corresponding signals to CPU when the mouse buttons are pressed.
- Joy Stick- To move cursor position on a monitor screen. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
- Light pen- It is used to select a displayed menu item or draw pictures on the monitor screen.
- Track Ball- Mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on ball, pointer can be moved.
- Scanner- A scanner allows you to scan printed material and convert it into a file format that may be used within the PC.
- Digitizer- It converts analog information into digital form.
- Microphone-Microphone is an input device to input sound that is then stored in digital form.
- Magnetic Ink Card Reader (MICR)-MICR input device is generally used in banks because of a large number of checks to be processed every day.
- Optical Character Reader (OCR)- OCR scans text optically character by character, converts them into a machine-readable code and stores the text on the system memory.
- Bar Code Reader- A device used for reading bar coded data (data in form of light and dark lines). Barcoded data is generally used in labeling goods, numbering the books.
- Optical Mark Reader(OMR)- A special type of optical scanner used to recognize the type of mark made by pen or pencil.
B. Output Devices: (How it shows you what it is doing) Output devices translate the computer’s output into the form understandable by
Monitors: Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.
There are two kinds of viewing screen used for monitors.
- Cathode-Ray Tube (CRT): The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution
- Flat- Panel Display: The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the
Printer: Printer is an output device, which is used to print information on paper.
- Impact Printers: The impact printers print the characters by striking them on the ribbon which is then pressed on the
- Non-Impact Printers: Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Laser Printers, Inkjet Printers.
- Data: Data can be defined as a representation of facts, concepts or instructions in a formalized manner which should be suitable for communication, interpretation, or processing by human or electronic
- Information:- Information is organized or classified data which has some meaningful values for the receiver. Information is the processed data on which decisions and actions are
- Data Processing Cycle: Data processing is the re-structuring or re-ordering of data by people or machine to increase their usefulness and add values for particular Data processing consists of basic steps input, processing and output.
These three steps constitute the data processing cycle.
- Input -Input data is prepared in some convenient form for processing. The form will depend on the processing machine. For example, when electronic computers are used, the input data could be recorded on any one of several types of input medium, such as magnetic disks, tapes and so on.
- Processing – In this step input data is changed to produce data in a more useful form. For example, paychecks may be calculated from the time cards, or a summary of sales for the month may be calculated from the sales orders.
- Output – The result of the proceeding processing step are collected. The particular form of the output data depends on the use of the data. For example, output data may be pay-checks for employees.
Disclaimer – The study materials are provided from the personal notes of a JRF Qualified. Need suggestions for any publishing or conceptual mistakes. Feel free to comments with your suggestions or clarifications.