What is Computer? (their components, classifications and characteristics)

Introduction:

A computer is a general-purpose machine that manipulates raw facts, according to a set of instruction that is fit into it. It is actually a combination of both hardware and software that transforms data into information and performs calculations. So, one can say it is an electronic device that is used for storing and processing data and information.

What is Computer?

A computer is a digital electronic device that accepts the data from the user, processes it by performing a variety of operations and calculations by using software to generate the result (see Figure 1.1). It needs both hardware and software in order to be useful.

Now before proceeding further there are few terms that need to understand:

1. Data: Raw facts or figures that need to be processed.

2. Information: Meaningful data which is processed, organized, and presented in an understandable form.

3. Instruction: Command that tells the computer what to do.

4. Processing: Sequence of action taken on data to convert it into information.

5. Hardware: The physical components of the computer.

6. Program: The instructions that tell the computer what to do, either in a sequential or non-sequential manner.

7. Software: A sequence of instructions given to the computer which you want the computer to perform a particular task.

Classification of Computer

Computers are classified according to their size and the purpose of work, which are described as follows.

On the basis of size:

1. Microcomputer

These types of computers are widely used by single-user and are small in size and cheaper.

Types of Microcomputer:

• Desktop Computer/Personal Computer :

Input, processing, memory, and output units are self-contained and are housed within a horizontal or vertical case called the system unit.

• Notebook/UltraBook/Laptop: An extremely lightweight computer, which uses flat panel technology, and can be moved from place to place. These types of computers consume less battery.

• Netbook: It is similar to a notebook but is smaller and less expensive. It is widely used for wireless communication or access to the Internet.

• Handheld Computer/ Palmtop: Extremely small portable computer, having a small screen and stores programs and data within the unit or on a memory card.

• Tablet Computer: These are lighter notebook computers having a smaller screen, in which input is given either by touch screen or by pen called a stylus, For example, Ipad.

• Smartwatch: A smartwatch or watch phone is a computerized wristwatch or a wearable computer, which offers full mobile phone feature-capability thus allowing users to make or answer phone calls, send or receive text Whatsapp messages. It is used to perform some basic tasks such as calculations, translations, game playing. By using a mobile operating system one can also run mobile apps smartwatches can be customized according to one's need.

Smartwatches function as portable media players, thus offering playback of FM (Frequency modulation )radio audio, and video files to the user via a Bluetooth headset. It also supports wireless technologies like the BlueTooth headset.

Some are Widely Used watches are:

Matorola: Motorola motoactv, moto 360
Samsung: Samsung Galaxy Gear, Gear 2, Gear 2 Neo and Gear Fit, Gear Live, Gear S.
Apple: Apple Watch

2. Minicomputer: These types of computers are smaller in size and are less powerful than mainframe computers, and it is a multi-user device, used to carry out some specific tasks in engineering and Computer-Aided Design (CAD).

3. Mainframe: These are large, powerful, expensive computers used by organizations to connect thousands of users simultaneously. This computer contains specialized hardware and software, for processing millions of transactions.

4. Supercomputer: It is the fastest, most expensive machine available today and used to carry an immense amount of mathematics calculations. supercomputers are used in weather forecasting, scientific simulation, and nuclear research.

On the Basis of work:

1. Analog computers: These types of computers use continuous physical phenomena having specific magnitude, such as electrical and mechanical quantities to model the problem being solved. Operations are performed on it by manipulating

and processing the data.

2. Digital computers: Digital computers process information which is in a binary or two-state form, namely zero and one. Digital computers fall into ranges called microcomputers, minicomputers, mainframes, and supercomputers. It can produce desired graphics, sound.

3. Hybrid computer (Analog +Digital): This type of computer is capable of inputting and outputting data in both analog and digital forms. It is basically a digital computer that accepts analog signals and converts them into digital forms for processing.

The major components of digital computers are:

1. Central Processing Unit(CPU)

2. Input and output unit

3. Memory unit

Central Processing Unit (CPU)

The CPU is the brain of a computer. Its primary job is to run programs and perform the logical, arithmetic, input/output operation of the system. A block diagram of the basic computer organization is shown.

The speed of the CPU depends upon the type of microprocessor used. An operation, namely inputting, storing, processing, outputting, and controlling the data, is carried out by all computer systems.

The five units are:

• Inputting: Process of entering data into the computer by the user, using an input device.

• Storing: Holding of data and instructions in the computer's main memory for manipulations.

• Processing: Performing operations (both arithmetic and logical) or manipulation of data.

• Outputting: Process of showing the information or result to the user either on-screen (monitor) or on paper (through printer).

• Controlling: Directing all the above processes, incoordination, with the Control Unit (CU) in a Central Processing Unit (CPU).

1. Arithmetic Logic Unit (ALU): Fundamental building block of CPU, where the actual execution of instructions takes place. It loads data from input register, and performs the operations as directed by a control unit, and then stores the result in the output register.

All ALUs are designed to perform:

• Arithmetic operations: Add, subtract, multiply, divide.

• Logical operations: AND, OR, NOT, '(XOR.

• Comparison operations: Less than, equal to, greater than, less than equal to, greater than equal to.

• Bit-shifting operations: Shifting the word by a specific number of bits either to left or right.

2.Control Unit (CU): It controls the entire working of the computer by generating timing and control signals. It also controls the transfer of data between memory and input/ output devices, operations, and entire processing.

3. Memory Unit: It holds the data which is currently manipulated by the CPU. It has primary and secondary memory. Intermediate results generated in the ALU are temporarily stored in the memory unit prior to processing and are transferred as when needed, to the ALU. No processing is done in the memory unit.

1. Primary Memory/Main Memory: Input data before processing needs to be brought into primary memory. Instruction needed for processing, intermediate result, and the final output stores in this memory.

2. Secondary Memory/Auxiliary Memory: This stores data, output, and programs permanently. This unit does not directly link with the CPU.

Inguinal Output Devices/ Peripheral Devices

Input/output devices are used to communicate with the computer, either by entering the data into a computer or by displaying the results of processing.

Input Devices

Input devices are the hardware device that sends data and instruction into a computer system.

Some of the input devices are explained as follows:

1. Keyboard: and data are entered into a computer through a keyboard. It contains alphabets, digits, special characters, function keys, and some control keys. When a key is pressed, an electronic signal is produced which is detected by an electronic circuit called a keyboard encoder.

Types of keys on the keyboard:

• Alphanumeric keys: It includes all the numbers and letters on the keyboard. e.g., A-Z and 0-9.

• Functions key: Keys from Fl to F12.

• Punctuation keys: These include a comma (,) semicolon (:)

• Special keys: These include controls keys, Arrows key, Caps Lock key, Delete key.

• Pointing device: Communication, such as sending the command signals to the computer; selecting items from the screen; selecting commands from the command menu can be done by pointing to the locations on the monitor, with the help of the pointing device.

Some of the common Input Devices are:

2. Mouse: It performs functions by detecting two-dimensional motion. It is held in one hand and moved across a flat surface, generally, it consists of two buttons: left and right buttons.

Types of the Mouse:

• Mechanical mouse: Movement to the cursor is relative to the movement of the ball present at the bottom of the mouse.

• Optical mouse: It uses a light-emitting diode for detecting movement.

• Wireless mouse: It relays the signal to a base station, which is wired to the computer's mouse port.

• Laser mouse: It uses an infrared light-emitting diode.

3. Joystick: A joystick is used to move the cursor continuously in . the previously pointing direction on a monitor screen. It consists of a stick that pivots on a spherical ball on its base and can be moved in a clockwise or anticlockwise direction It is used for playing computer games.

4. Graphics tablet/Digitizer/ Digitizing Tablet: It consists of an electronic writing area and a pressure-sensitive pen for getting different strokes of various widths.

5. Touch Screen: It's an electronic visual display that detects the touch within a display area. The touch screen sends a signal to the computer which gives the location on the screen which has been touched. It works as a touch sensor, controller (PC card which translates PC understandable information), and software driver.

6. Touchpad/Trackpad: It translates motion and position of user's fingertip to relative position on the screen. It is used in laptops.

7. Trackball: It has a ball on its top, which can be rolled by a finger. It is widely used in CAD (Computer-Aided Design) workstation, Radar (Radio Detection and Ranging) consoles in air traffic control room and Sonar (Sound Navigation and Ranging) equipment on a ship.

8. Scanner: Information in the form of text or image is entered and then transformed into a digital file, which allows the computer to read or display the scanned object.

9. OMR (Optical Mark Reader): It is a special scanner used for recognizing a pre-specified type of mark made by pencil or pen. OMR focuses light on the page being examined and the light pattern reflected from the dark marks is then detected.

10. Voice Input and Recognition System: It consists of a microphone or telephone that converts human speech into electrical signals, which is sent to the computer where it is matched against pre-stored patterns to identify the input. When a close match is found, a word is recognized by the system. The set of pre-stored patterns is known as the vocabulary of the system.

11. Bar-code Reader: It is used to read bar-coded data (Universal Product Code) for fast identification of items. It consists of a series of small lines, known as bars. The light-sensitive detector of the barcode reader identifies bar code image and then converts it into numeric code It is used to reduce the amount of data entry for routine transactions.

12. MICR (Magnetic Ink Character Recognition): It is a character-recognition technology that detects the special encoded characters on bank cheques and deposit slips After detecting the encoded characters, it converts them into digital data for the computer. It can read up to 2400 documents per minute. The coding system of MICR Figure MICR contains only 14 characters.

13. Microphone (Mic): It converts the received sound into a computer's format called digitized sound or digital audio. A sound card is used to convert voice into digital form.

14. OCR (Optical Character Recognition): It converts scanned images into machine-encoded text. It uses photoelectrié devices Mic to scan the character being read and convert the reflected light pattern of data into binary form.

15. Web Camera (Webcam): It is attached to a computer and accepts input just by focusing on an object. An image so taken can be transferred over the network to a distant place It is widely used in video conferencing or online chatting Nowadays, web cameras are embedded into a display with a laptop or are connected via US (Universal Serial Bus).

16. Digital Camera (Digicam): It stores pictures or videos in electronic form, it has an LCD display screen that allows the user to view and save photos or videos.

17. Video Camera: It takes continuous pictures and generates a signal for display on a monitor.

18. Biometric Sensors: It recognizes the physical or behavioral traits of an individual. It is widely used for security purpose as they work with accuracy.

Output Devices

Output devices are those devices of computer systems that display the results to the outside world either in the form of hardcopy (printer) or softcopy (monitor).

Some of the common Output Devices are as follows:

1. Monitors: This is an electronic visual display, comprising of the display device, circuitry, and an enclosure, used to display the output. The picture on a monitor is made up of thousands of tiny colored dots called pixels.

Types of monitor:

• CRT (Cathode ray tube): The first computer monitors used cathode ray tubes. It contains an electron gun at the back, which fires electrons at the group of phosphor dots, as a result, the phosphor dot glows and gives the color.

• LCD (Liquid crystal display): These are lightweight computer monitors used in laptops and notebooks where the power consumption is less. TFT-LCD is a variant of LCD which is now is a dominant technology and is used for computer monitors.

• LED (Light-emitting diode): It emits light when an electric current is passed through it.

• OLED (Organic light-emitting diode): These monitors provide higher contrast and better viewing angles.

3-D Monitors: It conveys depth perception to the viewer. It gives an experience of virtual reality and is expensive.

2. Printers: It produces a hard copy of documents that are stored in an electronic form on physical print media. It converts what was on the screen into print when the print command is given.

The printers can be classified as:

Impact Printer: The impact printer uses an electromechanical mechanism that causes hammers or pins to strike against a ribbon and paper to print the text.

Types of Impact printer are:

• Dot-matrix printer: It uses a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper. It prints one character at a time and can print multi-layer forms, special characters, and graphics.

• Daisy-wheel printers: It uses wheel as a print head, which rotates and then the hammers strike on the backside of the spoke and press it against the paper to print a character. They cannot produce high-quality print graphics.

• Line printers: It is a high-speed printer, which prints an entire line at a time. It produces a lot of noise.

• Drum printer: It is an old line printing technology, which is used to print character images around the cylindrical drums.

Non-impact printers: Non-impact printers use thermal, chemical, electrostatic, laser beam, or inkjet technology for printing the text, and their printing head does not strike the paper. Usually, a non-impact type printer is faster and there is no mechanical contact between the paper and the print head.

Types of Non-impact printer:

• Laser printers: These printers print one page at a time and use laser light sources to produce an image on a photosensitive drum. The computer controls the laser beam to turn it on and off when it is sent back and forth across the drum.

• Electromagnetic printer: These are the fast printer, which falls under the category of the page printers.

• Thermal printer: Printing quality is very poor, and ink printed on paper gets weaker over time. These types of printers are widely used in petrol pumps, Bank ATMs, etc.

• Electrostatic printer: It is used for large format printing, as they print fast thus making the low cost.

• Inkjet printer: It fires droplets of ink on paper to create the text impression, as its print head contains tiny nozzles of different colors.

3. Plotters: These are used to produce precise, good quality graphics and drawings under the control of the computer, by using an ink pen or inkjet.

There are two types of a plotter, one that uses a pen (drum and flatbed plotter) and the other that does not use a pen (electrostatic plotter).

• Drum plotter/roller plotter: It consists of a roller on which a paper is placed and the mechanical device is known as a robotic drawing arm, which moves side-to-side as the paper is rolled back and forth through the roller.

• Flatbed plotter/ table plotter: It contains a long stationary horizontal surface on which the paper is fixed, and the pen is allowed to move along the horizontal and vertical axis.

• Electrostatic plotter: It creates an image by marking the paper with electrostatic charges, and thus producing a high-quality image for commercial artists.

4. Projector: It is connected to a PC and used to project information from a computer onto a large screen so that a large number of people can view the information. It is widely used for giving presentations

5. Speech Synthesizer: It converts textual data into spoken sentences. To produce the speech, basic sound units called phonemes are combined. The sequence of words in a text is combined into phonemes, amplified, and outputted through a speaker attached to a computer.

6. Speaker: It receives sound in form of electric current for sound card and then converts it into a sound format.