FOC–Introduction to Computers (Unit 1) Solved Question Papers 16 Marks



1. Define computer. Explain the characteristics briefly? (MAY 2009\FEB 2009)

A computer is a programmable machine or device that performs pre-defined or programmed computations or controls operations that are expressible in numerical or logical terms at high speed and with great accuracy.

Characteristics of Computers

· Speed

· Accuracy.

· Automation.

· Endurance.

· Versatility.

· Storage.

· Cost Reduction.

2. With suitable examples, explain about Number systems. (JAN 2009)

A number system is a set of rules and symbols used to represent a number. There are several different number systems. Some examples of number systems are as follows:

· Binary (base 2)

· Octal (base 8)

· Decimal (base 10)

· Hexadecimal (base 16)

Decimal and Hexadecimal numbers can each be represented using binary values. This enables decimal, hexadecimal, and other number systems to be represented on a computer which is based around binary (0 or 1 / off or on). The base (or radix) of a number system is the number of units that is equivalent to a single unit in the next higher counting space. In the decimal number system, the symbols 0-9 are used in combination to represent a number of any sizes.

For example, the number 423 can be viewed as the following string of calculations: (4 x 100) + (2 x 10) + (3 x 1) = 400 + 20 + 3 = 423

3. Describe evolution of computer? (JAN 2009 / MAY 2009)

· Abacus

· Astrolabe

· Pascaline

· Stepped Reckoner

· Difference Engine

· Analytical Engine

· Punch Cards

· ENIAC (Electrical Numerical Integrator and Calculator)

· Von Neumann Machine

4. Explain various generations of computers with features? (FEB 2009/FEB 2010)

Generation of Computers

Each phase of computer development is known as a separate generation of computers. The computer can be classified into four generations according to their type of electronic circuits such as vacuum tube, transistor, IC etc.

(a) The First Generation Computers (1949-55)

Main Features:

1) The computers of this generation used vacuum tubes.

2) These computers used machine language for giving instructions.

3) They used the concept of stored program.

4) These computers were 5000 times faster than the MARK-I.

5) The first generation computers were welcomed by Government and Universities.


1) These computers were very big in size. The ENIAC machine was 30 x 50 feet in size and

30 tons in weight. So, these machines required very large space for their workings.

2) Their power consumption was very high.

3) These computers had slow operating speed and small computing capacity.

4) These computers had a very small memory.

(b) The Second Generation Computers (1956-65) Main Features:

1) The computers of this generation replaced vacuum tubes with transistors.

2) Magnetic cores were invented for storage.

3) Different magnetic storage devices were developed in this generation.

4) Commercial applications were developed during this period. Eighty percent of these computers were used in business and industries.

(c) Third Generation Computers (1966-75) Main Features:

· The third generation computers replaced transistors with’ Integrated Circuits’. These

Integrated Circuits are also known as chips.

· The size of main memory was increased and reached about 4 megabytes.

· Magnetic disk technology had been improved and drive having capacity upto 100

MBPS came into existence.

· The CPU becomes more powerful with the capacity of carrying out 1 million instructions per second.

· This generation computers were relatively inexpensive and faster.

· The application area also increased in this generation. The computers were used in other areas like education, small businesses survey, analysis along with their previous usage areas.

(d) The Fourth Generation Computers (1976-Present) Main Features:

i.The fourth generation computers replaced small scale integrated circuits and medium scale integrated circuits with the microprocessors chip.

ii. Semiconductor memories replaced magnetic core memories.

iii. The hard-disks are available of the sizes upto 200 GB. The RAID technology

(Redundant Array of Inexpensive Disks) gives storage upto thousands of GB. iv. Computer cost came down rapidly in this generation.

v. Application of computers is increased in various areas like visualization, parallel computing, multimedia etc.

(e) The Fifth Generation Computers

Mankind along with the advancement in science and technology is working hard to bring the Vth Generation of computer. These computers will have the capability of thinking on their own like an man with the help of Artificial Intelligence (AI). the 21st century will be better, faster, smaller and smarter computers.

5. Explain the fundamental units of a computer with a block diagram? (Or)

Explain the basic computer organization in detail? (JAN 2009\MAY 2009)

A computer can process data, pictures, sound and graphics. They can solve highly complicated problems quickly and accurately.

Input Unit:

Computers need to receive data and instruction in order to solve any problem. Therefore we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform the following functions.

· Accept the data and instructions from the outside world.

· Convert it to a form that the computer can understand.

· Supply the converted data to the computer system for further processing.


Storage Unit:

Block Diagram of Computer

The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use.

Types of Storage Devices:

1. Primary Storage:

1. Stores and provides very fast.

2. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program.

3. The primary memory is temporary in nature. The data is lost, when the computer is switched off.

4. In order to store the data permanently, the data has to be transferred to the secondary memory. The cost of the primary storage is more compared to the secondary storage.

2. Secondary Storage:

1. It stores several programs, documents, data bases etc.

2. The programs that run on the computer are first transferred to the primary memory before it is actually run.

3. Whenever the results are saved, again they get stored in the secondary memory.

4. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc.,

Memory Size:

All digital computers use the binary system, i.e. 0’s and 1’s. Each character or a number is represented by an 8 bit code. The set of 8 bits is called a byte. A Character occupies 1 byte space. A numeric occupies 2 byte space. Byte is the space occupied in the memory. The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One KB is equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary storage in a typical PC usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB, 256MB memory are quite common.

Output Unit:

The output unit of a computer provides the information and results of a computation to

outside world. Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output devices are floppy disk drive, hard disk drive, and magnetic tape drive. Arithmetic Logical Unit:

All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition, subtraction, multiplication, division, etc and does logic operations viz, >, <, =, ‘etc. Whenever calculations are required, the control unit transfers the data from storage unit to ALU once the computations are done, the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results.

Control Unit:

It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user. It controls the flow of data and instructions from the storage unit to ALU. It also controls the flow of results from the ALU to the storage unit. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working.

Central Processing Unit:

The control unit and ALU of the computer are together known as the Central Processing Unit

(CPU). The CPU is like brain performs the following functions:

• It performs all calculations.

• It takes all decisions.

• It controls all units of the computer.

A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron, Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core, and AMD etc.

6. Explain the classification of computers? (MAY 2009\FEB 2009\FEB 2010)

Personal Computers:


A personal computer (PC) is a self-contained computer capable of input, processing, output, and storage. A personal computer is designed to be a single-user computer and must have at least one input device, one output device, a processor, and memory. The three major groups of PCs are desktop computers, portable computers, and handheld computers. Desktop Computers: A desktop computer is a PC designed to allow the system unit, input devices, output devices, and other connected devices to fit on top of, beside, or under a user’s desk or table. This type of computer may be used in the home, a home office, a library, or a corporate setting.

Portable Computers:

A portable computer is a PC small enough to be moved around easily. As the name suggests, a laptop computer fits comfortably on the lap. As laptop computers have decreased in size, this type of computer is now more commonly referred to as a notebook computer. Manufacturers recently began introducing a new type of computer called the tablet PC, which has a liquid crystal display (LCD) screen on which the user can write using a special-purpose pen, or stylus. Tablet PCs rely on digital ink technology that allows the user to write on the screen. Another type of portable computer, called a wearable computer, is worn somewhere on the body, thereby providing a user with access to mobile computing capabilities and information via the Internet.

 Handheld Computers:

An even smaller type of personal computer that can fit into the hand is known as a handheld computer (also called simply handheld, pocket PC, or Palmtop). In recent years, a type of handheld computer called a personal digital assistant (PDA) has become widely used for performing calculations, keeping track of schedules, making appointments, and writing memos. Some handheld computers are Internet-enabled, meaning they can access the Internet without wire connections. For example, a smart phone is a cell phone that connects to the Internet to allow users to transmit and receive e-mail messages, send text messages and pictures, and browse through Web sites on the phone display screen.


A workstation is a high-performance single-user computer with advanced input, output, and storage components that can be networked with other workstations and larger computers. Workstations are typically used for complex applications that require considerable computing power and high-quality graphics resolution, such as computer-aided design (CAD), computer-assisted manufacturing (CAM), desktop publishing, and software development. Midrange Servers:

Linked computers and terminals are typically connected to a larger and more powerful

computer called a network server, sometimes referred to as a host computer. Although the size and capacity of network servers vary considerably, most are midrange rather than large mainframe computers.

(i) Midrange server – formerly known as a minicomputer, a midrange server is a powerful computer capable of accommodating hundreds of client computers or terminals (users) at the same time.

(ii) Terminal – a device consisting of only a monitor and keyboard, with no processing capability of its own.

Mainframe Computers:

Larger, more powerful, and more expensive than midrange servers, a mainframe computer is capable of accommodating hundreds of network users performing different computing tasks. These computers are useful for dealing with large, ever-changing collections of data that can be accessed by many users simultaneously. Government agencies, banks, universities, and insurance companies use mainframes to handle millions of transactions each day.


A supercomputer is the fastest, most powerful, and most expensive of all computers. Many

are capable of performing trillions of calculations in a single second. Primary applications include weather forecasting, comparing DNA sequences, creating artificially intelligent robots, and performing financial analyses.

7. Describe briefly about Secondary storage devices? (MAY 2009)

Secondary storage devices, as indicated by the name, save data after it has been saved by the primary storage device, usually referred to as RAM (Random Access Memory). From the moment we start typing a letter in Microsoft Word, for example, and until we click on "Save," your entire work is stored in RAM. However, once you power off your machine, that work is completely erased, and the only copy remaining is on the secondary storage device where we saved it, such as internal or external hard disk drive, optical drives for CDs or DVDs, or USB flash drive.

Internal Hard Disk Drive

The internal hard disk drive is the main secondary storage device that stores all of your data

magnetically, including operating system files and folders, documents, music and video. The hard disk drive is a stack of disks mounted one on top of the other and placed in a sturdy case. They are spinning at high speeds to provide easy and fast access to stored data anywhere on a disk.

External Hard Disk Drive

External hard disk drives are used when the internal drive does not have any free space and

you need to store more data. In addition, it is recommended to always back up all of our data and an external hard drive can be very useful, as they can safely store large amounts of information. They can be connected by either USB connection to a computer and can even be connected with each other in case you need several additional hard drives at the same time.

Optical Drive

An optical drive uses lasers to store and read data on CDs and DVDs. It basically burns a series of bumps and dips on a disc, which are associated with ones and zeros. Then, this same drive can interpret the series of ones and zeros into data that can be displayed on your monitors. There are a few different types of both CD and DVD disks, but the main two types include R and RW, which stand for Recordable (but you can write information on it just once) and Rewritable (meaning you can record data on it over and over again).

USB Flash Drive

USB flash memory storage device is also portable and can be carried around on a key chain. This type of a secondary storage device has become incredibly popular due to the very small size of device compared to the amount of data it can store (in most cases, more than CDs or DVDs). Data can be easily read using the USB (Universal Serial Bus) interface that now comes standard with most of the computers.

8. Explain about memory in Computer System?


Write short notes on memory of a computer? (MAY


The Role of Memory

The term "memory" applies to any electronic component capable of temporarily storing data. There are two main categories of memories:

Internal memory that temporarily memorizes data while programs are running. Internal memory uses micro conductors, i.e. fast specialized electronic circuits. Internal memory corresponds to what we call random access memory (RAM).

Auxiliary memory (also called physical memory or external memory) that stores information over the long term, including after the computer is turned off. Auxiliary memory corresponds to magnetic storage devices such as the hard drive, optical storage devices such as CD-ROMs and DVD-ROMs, as well as read-only memories.

Technical Characteristics

(a) Capacity, representing the global volume of information (in bits) that the memory can store

(b) Access time, corresponding to the time interval between the read/write request and the availability of the data

(c) Cycle time, representing the minimum time interval between two successive accesses

(d) Throughput, which defines the volume of information exchanged per unit of time, expressed in bits per second

(e) Non-volatility, which characterizes the ability of a memory to store data when it is not being supplied with electricity

The ideal memory has a large capacity with restricted access time and cycle time, a high throughput and is non-volatile.

However, fast memories are also the most expensive. This is why memories that use different technologies are used in a computer, interfaced with each other and organised hierarchically.


The fastest memories are located in small numbers close to the processor. Auxiliary memories, which are not as fast, are used to store information permanently.

Types of Memories

Random Access Memory

Random access memory, generally called RAM is the system's main memory, i.e. it is a space that allows you to temporarily store data when a program is running.

Unlike data storage on an auxiliary memory such as a hard drive, RAM is volatile, meaning that it only stores data as long as it supplied with electricity. Thus, each time the computer is turned off, all the data in the memory are irremediably erased.

Read-Only Memory

Read-only memory, called ROM, is a type of memory that allows you to keep the information contained on it even when the memory is no longer receiving electricity. Basically, this type of memory only has read-only access. However, it is possible to save information in some types of ROM memory.

Flash Memory

Flash memory is a compromise between RAM-type memories and ROM memories. Flash memory possesses the non-volatility of ROM memories while providing both read and writes access However, the access times of flash memories are longer than the access times of RAM.

9. Elaborate the various Input and Output Devices?

Input/Output devices are required for users to communicate with the computer. In simple terms, input devices bring information INTO the computer and output devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system.

Some commonly used Input/Output devices are listed in table below.


(a) Keyboard

It is a text base input device that allows the user to input alphabets, numbers and

other characters. It consists of a set of keys mounted on a board.


Figure 1: The Keyboard

Alphanumeric Keypad

It consists of keys for English alphabets, 0 to 9 numbers, and special characters like + − / * ( ) etc.

Function Keys

There are twelve function keys labeled F1, F2, F3… F12. The functions assigned to these keys differ from one software package to another. These keys are also user programmable keys.

Special-function Keys

These keys have special functions assigned to them and can be used only for those specific purposes. Functions of some of the important keys are defined below.


It is similar to the ‘return’ key of the typewriter and is used to execute a command or program.


It is used to enter a space at the current cursor location.


This key is used to move the cursor one position to the left and also delete the character in that position.


It is used to delete the character at the cursor position.


Insert key is used to toggle between insert and overwrite mode during data entry.


This key is used to type capital letters when pressed along with an alphabet key. Also used to type the special characters located on the upper-side of a key that has two characters defined on the same key.

Caps Lock

Cap Lock is used to toggle between the capital lock features. When ‘on’, it locks the alphanumeric keypad for capital letters input only.


Tab is used to move the cursor to the next tab position defined in the document. Also, it is used to insert indentation into a document.


Control key is used in conjunction with other keys to provide additional functionality on the keyboard.


Also like the control key, Alt key is always used in combination with other keys to perform specific tasks.


This key is usually used to negate a command. Also used to cancel or abort executing programs.

Numeric Keypad

Numeric keypad is located on the right side of the keyboard and consists of keys having numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This keypad is provided to support quick entry for numeric data.

Cursor Movement Keys

These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down, left, right).

(b) Mouse

The mouse is a small device used to point to a particular place on the screen and select in order to perform one or more actions. It can be used to select menu commands, size windows, start programs etc. The most conventional kind of mouse has two buttons on top: the left one being used most frequently.

Mouse Actions

Left Click : Used to select an item.

Double Click : Used to start a program or open a file.

Right Click : Usually used to display a set of commands.

Drag and Drop : It allows you to select and move an item from one location to another. To achieve this place the cursor over an item on the screen, click the left

mouse button and while holding the button down move the cursor to where you want to place the item, and then release it.


(c) Joystick

Figure 2: The Mouse

The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It typically has a button on top that is used to select the option pointed by the cursor. Joystick is used as an input device primarily used with video games, training simulators and controlling robots


Figure 3: The Joystick



Scanner is an input device used for direct data entry from the source document into the computer system. It converts the document image into digital form so that it can be fed into the computer. Capturing

information like this reduces the possibility of errors typically experienced during large data entry.

Figure 4: The Scanner

Hand-held scanners are commonly seen in big stores to scan codes and price information for each of the items. They are also termed the bar code readers.

(e) Bar codes

A bar code is a set of lines of different thicknesses that represent a number. Bar Code Readers are used to input data from bar codes. Most products in shops have bar codes on them. Bar code readers work by shining a beam of light on the lines that make up the bar code and detecting the amount of light that is reflected back


Figure 5: The Bar Code Reader

(f) Light Pen

It is a pen shaped device used to select objects on a display screen. It is quite like the mouse (in its functionality) but uses a light pen to move the pointer and select any object on the screen by pointing to the object. Users of Computer Aided Design (CAD) applications commonly use the light pens to directly draw on screen.

(g) Touch Screen

It allows the user to operate/make selections by simply touching the display screen. Common examples of touch screen include information kiosks, and bank ATMs. (h)Digital camera


A digital camera can store many more pictures than an ordinary camera. Pictures taken using a digital camera are stored inside its memory and can be transferred to a computer by connecting the camera to it. A digital camera takes pictures by converting the light passing through the lens at the front into a digital image.


Figure 6: The Digital camera

(i) The Speech Input Device

The “Microphones - Speech Recognition” is a speech Input device. To operate it we require using a microphone to talk to the computer. Also we need to add a sound card to the computer. The Sound card digitizes audio input into 0/1s .A speech recognition program can process the input and convert it into machine-recognized commands or input.

Output Devices

(a) Monitor

Monitor is an output device that resembles the television screen and uses a Cathode Ray Tube (CRT) to display information. The monitor is associated with a keyboard for manual input of characters and displays the information as it is keyed in. It also displays the program or application output. Like the television, monitors are also available in different sizes.


(b) Liquid Crystal Display (LCD)

LCD was introduced in the 1970s and is now applied to display terminals also. Its advantages like low energy consumption, smaller and lighter have paved its way for usage in portable computers (laptops).

(c) Printer

Figure 8: The LCD

Printers are used to produce paper (commonly known as hardcopy) output. Based on the technology used, they can be classified as Impact or Non-impact printers. Impact

printers use the typewriting printing mechanism wherein a hammer strikes the paper through a ribbon in order to produce output. Dot-matrix and Character printers fall under this category. Non-impact printers do not touch the paper while printing. They use chemical, heat or electrical signals to etch the symbols on paper. Inkjet, Deskjet, Laser, Thermal printers fall under this category of printers.


When we talk about printers we refer to two basic qualities associated with printers: resolution, and speed. Print resolution is measured in terms of number of dots per inch (dpi). Print speed is measured in terms of number of characters printed in a unit of time and is represented as characters-per-second (cps), lines-per-minute (lpm), or pages-per-minute (ppm).

Figure 9: The Printer

(d) Plotter

Plotters are used to print graphical output on paper. It interprets computer commands and makes line drawings on paper using multicolored automated pens. It is capable of producing graphs, drawings, charts, maps etc. Computer Aided Engineering (CAE) applications like CAD (Computer Aided Design) and CAM (Computer Aided Manufacturing) are typical usage areas for plotters.

Figure 10: The Plotter clip_image021

(e) Audio Output: Sound Cards and Speakers:

The Audio output is the ability of the computer to output sound. Two components

are needed: Sound card – Plays contents of digitized recordings, Speakers – Attached to sound card.

10.Convert the numbers:

(a) Convert the following number to decimal (2) (35)10 (i) (11011011.100101)2



(b) Convert (231.3)4 to Base of 7 (4) Answer

Step 1: Convert from Base 4 to Base 10 (45.75)10

Step 2: Convert from Base 10 to Base 7 (63.515)7

(c) Convert the following Decimal numbers to Hexadecimal numbers (3 * 2 = 6)

(i) (35)10



(ii) (275)10



(iii) (31)10




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