Computer Appreciation - Unit I

 

UNIT – I

Computer Appreciation:

1. Introduction to computers,

2.  characteristics of computer;

3. History of computers

4 Classification of computers 

Based on size: (Micro, Mini, Mainframe and super computers)

Based on Working Principles 

Based on Generations; 

5.Applications of computers; 

6. commonly used terms–

Hardware, Software, Firmware.

7.Basic Computer Organization:

8. Block diagram of computer system, Input unit, Processing Unit and Output Unit

9. Description of Computer input devices: Keyboard, Mouse, Trackball, Pen, Touch screens, Scanner, Digital Camera

10. Output devices: Monitors, Printers, Plotters

1.   Introduction to computers:

A computer is an electronic machine or device that performs processes, calculations and operations based on instructions provided by a software or hardware program. It has the ability to accept data (input), process it, and then produce outputs. Computers can also store data for later uses and retrieve whenever it is necessary.

or

 

A computer is an electronic machine which can accept data in certain form, process the data and give the result of the processing in a specified format as information.

 

A computer system consists of two parts: hardware and software. Hardware is any electronic or mechanical part you can see or touch. Software is a set of instruction, called a program, which tells the computer what to do. There are three basic hardware sections: the Central Processing Unit (CPU), main memory, and peripherals.

 

 

2. Characteristics of Computer

Computer became very popular and more important part, unavoidable device of today’s world because of its characteristic like correct and dependable outputs, high speed and accuracy etc. Therefore the five Major characteristics of computers are given below:

Speed

Speed of a computer device is very fast as it can perform in a few seconds, the amount of calculation or anything that we are human being can do in an entire year or more.

Computers can do billions of calculations in a second. If the smallest unit of time for humans is a second, computers work by the followings

a) 1 millisecond =  1/1000 seconds      
b) 1 microsecond =1/1000000 seconds      
c) 1 nanosecond = 1/1000000000 seconds      
d) 1 picosecond = 1/1000000000000 seconds

Accuracy

Accuracy of a computer is consistent. Computer gives us accurate result or calculation.

Error occurs in result for any calculations in a computer are only due to wrong program or instruction, inaccuracy in input data etc.

Consistency

Computer is a consistent machine, it means that computer never gets tired of working more. You can use computer to perform your task without any error for any number of hours. It means computer system can work continuously for 24 hours a day and 365 days a year.

Data storage capacity

Computer can store huge amount of data in a small sized storage disk such as hard disk, CD, DVD, PenDrive, memory card etc.

Let's give you an idea that now a computer can store huge amount of data in a small storage disk. For example a Pen drive of 16 GB is enough to store the entire Encyclopaedia Britannica.

Flexibility

Flexibility means that a computer can work in many areas like you can use your computer system to:

·         Watch movies or videos

·         Listen sounds or music

·         Play games

·         See pictures

·         Write textual documents and save

·         Open and read anything

·         and many more

Versatility

The computer system is very versatile machine. The most wonderful feature of the activities of different types from simple calculation to the complex scientific operations and computations and is also capable of preparing the examination marks sheets, bills, letters, documents, and also the design and modelling of navigating missiles and satellites.

Automation

Computer programs can schedule tasks that a computer can execute without any interaction. Computer programs can also store procedures which computers can execute one after another, again and again.

No Logical Decision

Computer can’t think and take decision itself. But computer programs can be written in a way so that it takes logical decisions. Still, it is just the program written by humans, executed by the computer.

No IQ

Computer has speed, memory, accuracy but it cannot work itself. If not being instructed to do a thing, the computer is nothing but a useless machine. All its hardware power depends on coded instruction to perform their action. Thus it has no IQ

 

3. History of computers

The term 'Computer' was first introduced in 1640 and referred to as 'one who calculates'. It was derived from the Latin word 'computare', which meant 'to calculate'. In 1897, it was known as the 'calculating machine'. Later in 1945, the term 'computer' was introduced as 'programmable digital electronic computer, which is now called a 'computer'.

When the computers were introduced, they were large and could fill an entire room. Some computers were operated using large-sized vacuum tubes. In 1833, Charles Babbage (known as the father of the computer) invented an early calculator, which was named as the 'difference engine'. Later in 1837, he introduced the first mechanical, general-purpose computer 'Analytical Engine'. Over time, computers became powerful in performance and small in size.

 

4. Classification of computers:

Computers can be classified many different ways -- by size, by function, or by processing capacity.

 4.1. Classification of computers on size : (Micro, Mini, Mainframe and supercomputers),

Microcomputers

·         Microcomputers are connected to networks of other computers.

·         The price of a microcomputer varies from each other depending on the capacity and features   of the computer.

·         Microcomputers make up the vast majority of computers.

·         Single user can interact with this computer at a time.

·         It is a small and general purpose computer.

Mini Computer

Mini Computer is a small and general purpose computer.

·         It is more expensive than a micro computer.

·         It has more storage capacity and speed.

·         It designed to simultaneously handle the needs of multiple users

Mainframe Computer

·         Large computers are called Mainframes.

·         Mainframe computers process data at very high rates of speed, measured in the millions of instructions per second.

·         They are very expensive than micro computer and mini computer.

·         Mainframes are designed for multiple users and process vast amounts of data quickly. Examples: - Banks, insurance companies, manufacturers and airlines are typical users.

Super Computers

·         The largest computers are Super Computers.

·         They are the most powerful, the most expensive, and the fastest.

·         They are capable of processing trillions of instructions per second.

 

It uses governmental agencies, such as:-

·         Chemical analysis in laboratory

·          Space exploration

·          National Defense Agency

·          National Weather Service

·          Bio-Medical research

·          Design of many other machines

·

4.2. Classification of computers on Working Principles

Analog Computer

Analog computer is the special purpose computer. It represents the data ans physical quantities such as current , pressure, temperature, voltage etc. They were especially useful in the simulation and evaluation of dynamic situations such as flight of a space capsule or the changing weather patterns over a certain area. The accuracy of analog computers are low.

Examples: Speedometer, Odometer, Seismograph etc.

Digital Computer

Digital computer is the general purpose computer, it uses discrete data like letters, numbers , symbols etc. and process data in binary digits i.e 0s and 1s. It can be also powerful computers like super, mainframe, mini and micro computers. . It performs task to control industrial process and regulate the operations of machines, analyze and organize vast amount of  business data and simulate the behavior of dynamic systems. They are faster and accurate as compared to analog computer.

Hybrid Computer

The combination of computers which is capable of processing in both analog and digital signals. It accepts input in the form of analog signals , process data digitally and gives output either digitally or analog form. They are used in industrial application, airplanes, ships hospital etc. The widest application of hybrid computer take place in situation which require real time solutions. Example: ECG (Electronic Cardio Graph).

 Difference between Analog and Digital Computer

Analog Computer	Digital Computer
The computer which is based on continuous data.	The computer which is based on discrete data.
It measures only physical values like current, speed, voltage etc.	It measures digits i.e 0 and 1
It is used for specific purpose.	It is used for general purpose.
Low accuracy	High accuracy.
It has no memory or less memory.	It has high storage capacity.
They are slower than digital computer.	They are faster than analog computer.
The signals are in the form of curve line	The signals is in the form of pulse.

 

5. Applications of computers:

 

The various applications of computers in today's arena :

1. Business
2. Education
3. Marketing
4. Banking
5. Insurance
6. Communication
7. Health Care
8. Military
9. Engineering Design

› Business
A computer has high speed of calculation, diligence, accuracy, reliability, or versatility which made it an integrated part in all business organisations.
Computer is used in business organisations for: Payroll calculations, Sales analysis, Budgeting, Financial forecasting, Managing employees database and Maintenance of stocks etc.

› Education
Computers have its dominant use in the education field which can significantly enhance performance in learning. Even distance learning is made productive and effective through internet and video-based classes. Researchers have massive usage of these computers in their work from the starting to till the end of their scholarly work.

› Marketing
In marketing, uses of computer are :
Advertising - With computers, advertising professionals create art and graphics, write and revise copy, and print and disseminate ads with the goal of selling more products.
Home Shopping - Home shopping has been made possible through use of computerised catalogues that provide access to product information and permit direct entry of orders to be filled by the customers.

Banking
Today banking is almost totally dependent on computer. Banks provide the facilities of:
Banks provide online accounting facility, which includes current balances, deposits, overdrafts, interest charges, shares, and trustee records.
ATM machines are making it even easier for customers to deal with banks.

› Insurance
Insurance companies are keeping all records up-to-date with the help of computers. The insurance companies, finance houses and stock broking firms are widely using computers for their concerns.

Communication
Communication means to convey a message, an idea, a picture or speech that is received and understood clearly and correctly by the person for whom it is meant for. Some main areas in this category are: Chatting, E-mail, Usenet, FTP, Video-conferencing and Telnet.

› Health Care
Most of the medical information can now be digitized from the prescription to reports. Computation in the field of medicine allows us tooffer varied miraculous therapies to the patients. ECG’s, radiotherapy wasn’t possible without computers.

› Military
Computers are the main tools which help in developing missiles and other equipment in the deference system. Designing and the maintenance are possible only through computers. Computer builds the links between the soldiers and commanders through the satellite. Construction of weapons and controlling their function is not possible without the aid of computers. The list of the criminals and the records of the cops are maintained regularly in the system.

› Engineering Design
As per the title, computers aid in designing buildings, magazines, prints, newspapers, books and many others. The construction layouts are designed beautifully on system using different tools and software’s.

6. Commonly used terms–

Hardware, Software and Firmware

Hardware: 

Computer hardware is a collective term used to describe physical components of the computer. Computer hardware can be categorized as being either internal or external components.  
Internal hardware components are those necessary for the proper functioning of the computer like Motherboard,RAM, ROM and CPU etc.
External hardware components are attached to the computer to add or enhance functionality like keyboard, mouse and joystick etc.

Software :

Software is a set of instructions, data, or programs used to operate a computer and execute specific tasks. In simpler terms, software tells a computer how to function.

The two major types of computer software are:

Application software

System software

Firmware

It is a set of instructions programmed that is permanently etched into a hardware device like video cards, BIOS, keyboards, or hard drives. Without using special programs, it cannot be modifying or deleted by an end-user, unlike normal software.

8. Basic Computer Organization: Block diagram of computer system (Important)

Block diagram of a computer gives you the pictorial representation of a computer that how it works inside. Mainly computer system consists of three parts, that are central processing unit (CPU), Input Devices, and Output Devices. The Central Processing Unit (CPU) is divided into two parts again: Arithmetic Logic Unit (ALU) and the Control Unit (CU). The set of instruction is in the form of raw data.

A large amount of data is stored in the computer memory with the help of primary and secondary storage devices. The CPU is like the heart/brain of the computer. The user does not get the desired output, without the necessary option taken by the CPU.  The Central processing unit (CPU) is responsible for the processing of all the instructions which are given by the user to the computer system.

Input Unit

All the data received by the computer goes through the input unit. The input unit include different devices. like a mouse, keyboard, scanner, etc. In other words, each of these devices acts as a mediator between the users and the computer.

The data that is to be processed is put through the input unit. The computer accepts the raw data in binary form. It then processes the data, and produces the desired output.

The 3 major functions of the input unit are-

• Take the data to be processed by the user.
• Convert the given data into machine-readable form.
• And then, transmit the converted data into the main memory of the computer. The sole purpose is to connect the user and the computer. In addition, this creates easy communication between them.

 

 

 

CPU – Central Processing Unit

Central Processing Unit or the CPU, is the brain of the computer. It works the same way a human brain works. As the brain controls all human activities, the CPU too controls all tasks.

Moreover, the CPU conducts all the arithmetical and logical operations in the computer.

Now the CPU comprises of two units, namely – ALU (Arithmetic Logic Unit) and CU (Control Unit). Both of these units work in sync. The CPU processes the data as a whole.

Let us see what particular tasks are assigned to both units.

ALU – Arithmetic Logic Unit

The Arithmetic Logic Unit is made of two terms, arithmetic and logic. There are two major functions that this unit performs.

1. Data inserted through the input unit into the primary memory. Performs the basic arithmetical operation on it. Like addition, subtraction, multiplication, and division. It performs all sorts of calculations required on the data. Then sends back data to the storage.
2. The unit is also responsible for performing logical operations like, AND, OR, Equal to, Less than, etc.  In addition to this it conducts merging, sorting, and selection of the given data.

CU – Control Unit

The control unit as the name suggests is the controller of all the activities/tasks and operations. All this is performed inside the computer.

The memory unit sends a set of instructions to the control unit. Then the control unit in turn converts those instructions. After that these instructions are converted to control signals.

These control signals help in prioritizing and scheduling the activities. Thus, the control unit coordinates the tasks inside the computer in sync with the input and output units.

Memory Unit

All the data that has to be processed or has been processed is stored in the memory unit. The memory unit acts as a hub of all the data. It transmits it to the required part of the computer whenever necessary.

The memory unit works in sync with the CPU. This helps in faster accessing and processing of the data. Thus, making tasks easier and faster.

There are two types of computer memory-

1. Primary memory – This type of memory cannot store a vast amount of data. Therefore, it is only used to store recent data. The data stored in this is temporary. It can get erased once the power is switched off. Therefore, is also called temporary memory or the main memory.
   
   RAM stands for Random Access Memory. It is an example of primary memory. This memory is directly accessible by the CPU. It is used for reading and writing purposes. For data to be processed, it has to be first transferred to the RAM and then to the CPU.
2. Secondary memory – As explained above, the primary memory stores temporary data. Thus it cannot be accessed in the future. For permanent storage purposes,, secondary memory is used. It is also called the permanent memory or the auxiliary memory. The hard disk is an example of secondary memory. Even in a power failure data does not get erased easily.

 

 Output Unit 

The Output Unit of the computer provides the results of computation and information to the outside world. The output unit generally performs the reverse process of the input unit and it converts the machine language digitized information to electronic impulses that are readable by the output devices. The most commonly used output devices are the Visual Display Unit (VDU) also known as the monitor. Other common output devices are a projector, headphone, speaker, etc.

 

9.  Input devices:

Keyboard

Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions.

Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.

S.No	Keys & Description
1	Typing Keys These keys include the letter keys (A-Z) and digit keys (09) which generally give the same layout as that of typewriters.
2	Numeric Keypad It is used to enter the numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machines and calculators.
3	Function Keys The twelve function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Each function key has a unique meaning and is used for some specific purpose.
4	Control keys These keys provide cursor and screen control. It includes four directional arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc).
5	Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

 

Mouse:

Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed.

Generally, it has two buttons called the left and the right button and a wheel is present between the buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer.

Advantages

• Easy to use
• Not very expensive
• Moves the cursor faster than the arrow keys of the keyboard.

 

Trackball:

Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved.

Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button, or a square.

 

Pen:

Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube.

When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.

Scanner:

Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation.

Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed.

Bar Code Readers

Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner.

Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to.

Optical Mark Reader (OMR)

OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.It is specially used for checking the answer sheets of examinations having multiple choice questions.

Microphone

Microphone is an input device to input sound that is then stored in a digital form. The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music.

Digital Camera

A digital camera is an input device that captures images (and sometimes video) digitally.  Digital cameras use an image sensor chip to capture the image, rather than the film used by a traditional camera.

Touch screens

A touch screen is a display device that allows the user to interact with a computer using their finger or stylus. They're a useful alternative to a mouse or keyboard for navigating a GUI (graphical user interface). Touch screens are used on a variety of devices, such as a computer and laptop displays, smartphones, tablets and information kiosks.

10. Output devices:

There is a two types of output.
A hard copy is a printed form of a digital document file from a computer on paper or any other material that may be transparent. A soft copy is a form of digital document file saved on a computer or drive. It is an electronic version of any document- not printed on paper. 

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)
• Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT −

• Large in Size
• High power consumption

Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

The flat-panel display is divided into two categories −

·        Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).

·        Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

 

Printers

Printer is an output device, which is used to print information on paper.

There are two types of printers −

• Impact Printers
• Non-Impact Printers

Impact Printers

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

Characteristics of Impact Printers are the following −

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image

These printers are of two types −

• Character printers
• Line printers

Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

• Dot Matrix Printer(DMP)
• Daisy Wheel

Dot Matrix Printer

In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.

Advantages

• Inexpensive
• Widely Used
• Other language characters can be printed

Disadvantages

• Slow Speed
• Poor Quality

Daisy Wheel

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.

Advantages

• More reliable than DMP
• Better quality
• Fonts of character can be easily changed

Disadvantages

• Slower than DMP
• Noisy
• More expensive than DMP

Line Printers

Line printers are the printers which print one line at a time.

These are of two types −

• Drum Printer
• Chain Printer

Drum Printer

This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.

Advantages

• Very high speed

Disadvantages

• Very expensive
• Characters fonts cannot be changed

Chain Printer

In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

Advantages

• Character fonts can easily be changed.
• Different languages can be used with the same printer.

Disadvantages

• Noisy

Non-impact Printers

Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

These printers are of two types −

• Laser Printers
• Inkjet Printers

Characteristics of Non-impact Printers

• Faster than impact printers
• They are not noisy
• High quality
• Supports many fonts and different character size

Laser Printers

These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

Advantages

• Very high speed
• Very high quality output
• Good graphics quality
• Supports many fonts and different character size

Disadvantages

• Expensive
• Cannot be used to produce multiple copies of a document in a single printing

Inkjet Printers

Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

They make less noise because no hammering is done and these have many styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

Advantages

• High quality printing
• More reliable

Disadvantages

• Expensive as the cost per page is high
• Slow as compared to laser printer

 

 

Plotters

Plotters are a special type of output device. It is suitable for applications:

1. Architectural plan of the building.
2. CAD applications like the design of mechanical components of aircraft.
3. Many engineering applications.

Advantage:

1. It can produce high-quality output on large sheets.
2. It is used to provide the high precision drawing.
3. It can produce graphics of various sizes.
4. The speed of producing output is high.

Drum Plotter:

It consists of a drum. Paper on which design is made is kept on the drum. The drum can rotate in both directions. Plotters comprised of one or more pen and penholders. The holders are mounted perpendicular to drum surface. The pens are kept in the holder, which can move left to the right as well as right to the left. The graph plotting program controls the movement of pen and drum.

Flatbed Plotter:

It is used to draw complex design and graphs, charts. The Flatbed plotter can be kept over the table. The plotter consists of pen and holder. The pen can draw characters of various sizes. There can be one or more pens and pen holding mechanism. Each pen has ink of different color. Different colors help to produce multicolor design of document. The area of plotting is also variable. It can vary A4 to 21'*52'.

 

 

 

EXERCISES

Long Question :

 

1. What is a Computer? List & explain some important characteristics of a computer.

2. Draw a block diagram to illustrate the basic organization of a computer  system and explain the function of the various units.

3. What is a Computer? Briefly explain the functionality wise classification of computer.