FOC Notes Unit 1 and Unit 2

7/30/2019 FOC Notes Unit 1 and Unit 2

1/46

NOTES ON FUNDAMENTALS OF COMPUTER AND PROGRAMMING ON UNIT IAND UNIT II

SYLLABUS AS PER UTTRAKHAND TECHNICAL UNIVERSITY

UNIT-I

Introduction to Computer Systems; Data representation: Number systems, character representation

codes, Binary, hex, octal codes and their inter conversions. Binary arithmetic, Floating point arithmetic,

signed and unsigned numbers IEEE standards, CPU organization, ALU, registers, memory, the idea of

program execution at micro level. Concept of computing, contemporary Operating Systems such as DOS,

Windows, UNIX etc. (only brief user level description). Introduction to organization and architecture of

mainframe, mini and micro systems.

UNIT-II

Concept of flow chart and algorithm; Algorithms to programs: specification, top-down development and

stepwise refinement ,Introduction to the design and implementation of correct, efficient and

maintainable programs, structured Programming, Use of high level programming language for the

systematic development of programs, programmability and programming languages, Object codes,

compilers. Introduction to the Editing tools such as vi or MS-VC editors.

(Possible Theoritical Questions and Answers From Unit 1 &2)

Question No: (1) Define computers? Why computer is known as data processing system?

What are the basic operations of Computer?

Answer: Computer: A computer is a programmable machine or device that performs pre-defined

or programmed computations or controls operations that are expressible in numerical or logicalterms at high speed and with great accuracy.

Computer is a fast operating electronic device, which automatically accepts and store input data,

processes them and produces results under the direction of step by step program.

Any Process that uses a computer program will enter data and summarize, analyze or otherwise

convert data into usable information. The process may be automated and run on a computer.

It involves recording, analyzing, sorting, summarizing, calculating, disseminating and storing data. Thus

Computer is known as data processing system.

Its various operations are:

1) It accepts data or instructions by way of input.

2) It stores data.

3) It can process data as required by the user.

4) It gives results in the form of output.

B.TECH-I SEM/FOC/THEORITICAL NOTES ON UNIT-I AND II BY DHEERAJ MURARI Page 1


2/46

5) It controls all operations inside a computer.

QuestionNo:(2). What is Data and Information? Give the applications of computer? What are

the characteristics of computers?

Answer: Data -Data is the fact or raw material for the information processing.

Information The processed data is called information.

Applications ofcomputer

Word Processing

Internet

Desktop publishing

Digital video or audio composition

Mathematical Calculations

Robotics

Weather analysis

Characteristics ofcomputers

Speed

Accuracy.

Automation.

Endurance.

Versatility.

Storage.

Cost Reduction.

Question No:(3). How will you classify computer systems?

Answer: Based on physical size, performance and application areas, we can generally divide computers

into four major categories:

1. Micro computer

2. Mini Computer

3. Mainframe computer and

4. Super Computer

Personal computers/Micro computers: A small, relatively inexpensive computer designed for an

individual user. In price, personal computers range anywhere from a few hundred dollars to thousands

of dollars. All are based on the microprocessor technology that enables manufacturers to put an

entire CPU on one chip.

Example:



3/46

Businesses use personal computers forward processing, accounting, desktop publishing, and for

running spreadsheet and database management applications. At home, the most popular use for

personal computers is for playing games.

Mainframe computer

Mainframes are computers used mainly by large organizations for critical applications, typically

bulk data processing such as census, industry and consumer statistics, enterprise resource planning,

and financial processing.

The term probably had originated from the early mainframes, as they were housed in enormous,

room-sized metal boxes or frames.

Mini computers:

A mini computer is a multi-user or time-sharing system. It is used for medium scale data processing such

as Bank account processing, Payroll processing etc., Mini computer process greater storage capacity and

larger memories as compared to micro computer.

Super computer

The fastest type of computer. Supercomputers are very expensive and are employed for specialized

applications that require immense amounts of mathematical calculations.

For example, weather forecasting requires a supercomputer. Other uses of supercomputers

include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum

exploration.

QuestionNo:(4). Explain the fundamental units of a computer with a block diagram? Explain

the basic computer organization in detail?

Answer: A computer can process data, pictures, sound and graphics. They can solve highly

Complicated problems quickly and accurately.



4/46

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 performthe 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.

e.g. Keyboard, Scanner, Mouse, Joystick, Mike etc

Storage Unit:

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:

(A) Primary Storage:

1. Stores and provides very fast.



5/46

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.

e.g. RAM, ROM etc

(B)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.,

e.g. CD-ROM, HDD, FLOPPY DRIVE etc

Memory Size:

All digital computers use the binary system, i.e. 0s and 1s. 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, >,


6/46

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.

QuestionNo:(5). With suitable examples, explain about Number systems?

Answer: 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 basedaround 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

QuestionNo:(6). Explain various generations of computers with features?

Answer: Generation ofComputers:

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 FirstGeneration Computers (1949-55)



7/46

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.

Limitations:

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)

MainFeatures:

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)

MainFeatures:

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)

MainFeatures:

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.



8/46

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.

QuestionNo:(6). Explain the classification of computers?

Answer: CLASSIFICATION OFCOMPUTERS

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 users desk or table. This type of computer may be used in the

home, a home office, a library, or a corporate setting.

PortableComputers:

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



9/46

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.

Workstations:

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/Minicomputers:

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.

Supercomputers:

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.

QuestionNo:(7). Explain Second Memory in detail?



10/46

Answer: 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.

Question No: (8). Explain about memory in Computer System?(or) Write short notes on

memory of a computer?

Answer: The Role of Memory: The term "memory" applies to any electronic component capable of

temporarily storing data.



11/46

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.

TechnicalCharacteristics

(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

organized 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 ofMemories

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.



12/46

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.

QuestionNo:(9). Elaborate the various Peripheral (Input and Output) Devices?

Answer: 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. Itconsists of a set of keys mounted on a board.

AlphanumericKeypad: 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-functionKeys

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.

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

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

Backspace-This key is used to move the cursor one position to the left and also delete the

character in that position.

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

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

Shift-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 thesame 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-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.



13/46

Ctrl-Control key is used in conjunction with other keys to provide additional functionality on the

keyboard.

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

specific tasks.

Esc-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

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

(d)Scanner

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. 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.



14/46

(e) Bar code Reader: 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

(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.

(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

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



15/46

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).

(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.

(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.

QuestionNo(10):Define Software & Hardware? What is an instruction? What are registers?

Answer: (10): Software:- Computer instructions or data, anything that can be stored electronically is

software. Computer software or just software is a general term used to describe the role that

computer programs, procedures and documentation in a computer system.

Hardware - (computer science) the mechanical, magnetic, electronic, and electrical components

making up a computer systemhardware. Hardware includes not only the computer proper but also the

cables, connectors, power supply units, and peripheral devices such as the keyboard, mouse, audio

speakers, and printers.

Instruction: An instruction is a basiccommand. The term instruction is often used to describe the

most rudimentaryprogramming commands. For example, a computer'sinstruction set is the

list of all the basic commands in the computer's machine language.

Register: A special, high-speed storage area within the CPU. All data must be represented in a

register before it can be processed. For example, if two numbers are to be multiplied, both

numbers must be in registers, and the result is also placed in a register.

QuestionNo:-(9): Give the categories of Software with example?



16/46

Answer: SOFTWARE TYPES

(A).Application Software:

Application Software is a set of programs for a specific application. Application software is useful for

word processing, accounting, and producing statistical report, Graphics, Excel and Data Base.

Programming languages COBOL, FORTRAN, C++,VB, VC, Java

Types of Application Software

Application software enables users to perform the activities and work that computers were designed

for. The specific type of application used depends on the intended purpose, and there are application

programs for almost every need.

(a) Individual application software refers to programs individuals use at work or at home. Examples

include word processing, spreadsheet, database management, and desktop publishing programs.

(b) Collaboration software (also called groupware) enables people at separate PC workstations to

work together on a single document or project, such as designing a new automobile engine.

(c) Vertical application software is a complete package of programs that work together to perform core

business functions for a large organization. For example, a bank might have a mainframe computer at

its corporate headquarters connected to conventional terminals in branch offices, where they are

used by managers, tellers, loan officers, and other employees. All financial transactions are fed to the

central computer for processing. The system then generates managers reports, account statements,

and other essential documents.

Other Application Software Models

Shareware: Shareware is software developed by an individual or software publisher who retains

ownership of the product and makes it available for a small contribution fee. The voluntary fee

normally entitles users to receive online or written product documentation and technical help.

Freeware: Freeware is software that is provided free of charge to anyone wanting to use it. Hundreds

of freeware programs are available, many written by college students and professors who create

programs as class projects or as part of their research.

Open Source Software: An open source software program is software whose programming code is

owned by the original developer but made available free to the general public, who is encouraged to

experiment with the software, make improvements, and share the improvements with the user

community

Question No (10): What do you understand by the compiler? What are various phases ofcompiler?



17/46

Answer: Compiler: A compiler is a computer program (or set of programs) that transforms source

code written in a programming language (the source language) into another computer language (the

target language, often having a binary form known as object code).

Various Phases ofCompiler: Following are various phases ofCompiler:

A common division into phases is described below. In some compilers, the ordering of phases may differslightly, some phases may be combined or split into several phases or some extra phases may be

inserted between those mentioned below.

Lexical analysis This is the initial part of reading and analysing the program text: The text is read and

divided into tokens, each of which corresponds to a symbol in the programming language, e.g., a

variable name, keyword or number.

Syntax analysis This phase takes the list of tokens produced by the lexical analysis and arranges these in

a tree-structure (called the syntax tree) that reflects the structure of the program. This phase is often

called parsing.

Type checking This phase analyses the syntax tree to determine if the program violates certain

consistency requirements, e.g., if a variable is used but not declared or if it is used in a context that does

not make sense given the type of the variable, such as trying to use a boolean value as a function

pointer.

Intermediate code generation The program is translated to a simple machine independent intermediate

language.

Register allocation The symbolic variable names used in the intermediate code are translated to

numbers, each of which corresponds to a register in the target machine code.

Machine code generation The intermediate language is translated to assembly language (a textual

representation of machine code) for a specific machine architecture.

Assembly and linking- The assembly-language code is translated into binary representation and

addresses of variables, functions, etc., are determined.

The first three phases are collectively called the frontend of the compiler and the last three phases are

collectively called the backend. The middle part of the compiler is in this context only the intermediate

code generation, but this often includes various optimizations and transformations on the intermediate

code.

Each phase, through checking and transformation, establishes stronger invariants on the things it passes

on to the next, so that writing each subsequent phase is easier than if these have to take all the

preceding into account. For example, the type checker can assume absence of syntax errors and the

code generation can assume absence of type errors. Assembly and linking are typically done by

programs supplied by the machine or operating system vendor,

Question No (11): Explain working of Loader, Linker, Interpreter and Assembler?



18/46

Answer: Loader: In a computer operating system, a loader is a component that locates a given program

(which can be an application or, in some cases, part of the operating system itself) in offline storage

(such as a hard disk), loads it into main storage (in a personal computer, it's called random access

memory), and gives that program control of the computer (allows it to execute its instruction s).

A program that is loaded may itself contain components that are not initially loaded into main storage,

but can be loaded if and when their logic is needed. In a multitasking operating system, a program that

is sometimes called a dispatcher juggles the computer processor's time among different tasks and

calls the loader when a program associated with a task is not already in main storage.

Linker: Also called link editor and binder, a linker is a program tha t combines object modules to form

an executable program. Many programming languages allow you to write different pieces of code,

called modules, separately. This simplifies the programming task because you can break a large program

into small, more manageable pieces. Eventually, though, you need to put all the modules together. This

is the job of the linker. In addition to combining modules, a linker also replaces symbolic addresses with

real addresses. Therefore, you may need to link a program even if it contains only one module.

The linkage editor accepts two major types of input:

Primary input, consisting of object decks and linkage editor control statements.

Additional user-specified input, which can contain both object decks and control

statements, or load modules. This input is either specified by you as input, or is incorporated

automatically by the linkage editor from a call library.

Output of the linkage editor is of two types:

A load module placed in a library (a partitioned data set) as a named member

Diagnostic output produced as a sequential data set.

The loader prepares the executable program in storage and passes control to it directly.

Interpreter: An interpreter normally means a computer program that executes, i.e. performs,

instructions written in a programming language. An interpreter may be a program that either

executes the source code directly

translates source code into some efficient intermediate representation (code) and

immediately executes this

explicitly executes stored precompiled code made by a compiler which is part of the

interpreter system

Assembler: An assembler translates an assembly language source program into machine codes.

Though the assembly language is the symbolic representation of machine codes, a computer

cannot understand it. After translating the assembly language program into machine codes by the

assembler, the program becomes ready for the execution.



19/46

Question No (12): Explain in detail the steps involved in Software Development Process?

Answer: Software development life cycle model is also called as waterfall model which is followed by

majority of systems.

This software development life cycle process has the following seven stages in it namely

1. System Requirements Analysis

2. Feasibility study

3. Systems Analysis and Design

4. Code Generation

5. Testing

6. Maintenance

7. Implementation

1.System Requirements Analysis:

The first essential or vital thing required for any software development is system. Also the system

requirement may vary based on the software product that is going to get developed. So a careful

analysis has to be made about the system requirement needed for the development of the product.

After the analysis and design of the system requirement phase the system required for the development

would be complete and the concentration can be on the software development process.

2.Feasibility study:

After making an analysis in the system requirement the next step is to make analysis of the

software requirement. In other words feasibility study is also called as software requirement analysis.

In this phase development team has to make communication with customers and make analysis of

their requirement and analyze the system. By making analysis this way it would be possible to

make a report of identified area of problem. By making a detailed analysis on this area a

detailed document or report is prepared in this phase which has details like project plan or schedule of

the project, the cost estimated for developing and executing the system, target dates for each phase of

delivery of system developed and so on. This phase is the base of software development process

since further steps taken in software development life cycle would be based on the analysis

made on this phase and so careful analysis has to be made in this phase.

3.Systems Analysis and Design:

This is an important phase in system development .Here analysis is made on the design of the system

that is going to be developed. In other words database design, the design of the architecture chosen,

functional specification design, low level design documents, high level design documents and so on

takes place. Care must be taken to prepare these design documents because the next phases

namely the development phase is based on these design documents. If a well structured and analyzed

design document is prepared it would reduce the time taken in the coming steps namely

development and testing phases of the software development life cycle.



20/46

4.Code Generation:

This is the phase where actual development of the system takes place. That is based on the design

documents prepared in the earlier phase code is written in the programming technology chosen. After

the code is developed generation of code also takes place in this phase. In other words the code is

converted into executables in this phase after code generation.

5.Testing:

A software or system which is not tested would be of poor quality. This is because this is the

phase where system developed would be tested and reports are prepared about bugs or errors in

system. To do this testing phase there are different levels and methods of testing like unit testing,

system test and so on. Based on the need the testing methods are chosen and reports are prepared

about bugs. After this process the system again goes to development phase for correction of errors and

again tested. This process continues until the system is found to be error free. To ease the testing

process debuggers or testing tools are also available.

To develop reliable and good quality Program/Software we need to follow the

following 5 steps :

1. Requirement Specification.

2. Analysis.

3. Design.

4. Implementation.

5. Verification and testing.

Question No (13): Explain the steps involved in developing a program? (or) Brief

about planning the computer program?

Answer: The Programming Process Purpose

1.Understand the problem

Read the problem statement

Question users

Inputs required

Outputs required

Special formulasTalk to users

2.Plan the logic

(a) Visual Design Tools

Input record chart



21/46

Printer spacing chart

Hierarchy chart

Flowchart

(b) Verbal Design Tools

Narrative Description

Pseudocode

3.Code the program

Select an appropriate programming language

Convert flowchart and/or Pseudocode instructions into programming language statements

4.Testthe program

1. Syntax errors

2. Runtime errors

3. Logic errors

4. Test Data Set

5. Implement the program

Buy hardware

Publish software

Train users

6.Maintain the program

Maintenance programmers

Legacy systems Up to 85% of IT department budget

Question No (14): Explain flowchart in detail?

Answer:A flowchart is a schematic representation of an algorithm or a stepwise process, showing the

steps as boxes of various kinds, and their order by connecting these with arrows. Flowcharts are used in

designing or documenting a process or program.

A flow chart, or flow diagram, is a graphical representation of a process or system that details the

sequencing of steps required to create output. A flowchart is a picture of the separate steps of a process

in sequential order.

The benefits of flowcharts are as follows:

a. Communication: Flowcharts are better way of communicating the logic of a system to all concerned.

b. Effective analysis: With the help of flowchart, problem can be analyzed in more effective way.



22/46

c. Proper documentation: Program flowcharts serve as a good program documentation, which is

needed for various purposes.

d. Efficient Coding: The flowcharts act as a guide or blueprint during the systems analysis and program

development phase.

e. Proper Debugging: The flowchart helps in debugging process.

f. Efficient Program Maintenance: The maintenance of operating program becomes easy with the help

of flowchart. It helps the programmer to put efforts more efficiently on that part.

Advantages

Logic Flowcharts are easy to understand. They provide a graphical representation of actions to be

taken.

Logic Flowcharts are well suited for representing logic where there is intermingling among many

actions.

Disadvantages

Logic Flowcharts may encourage the use of GoTo statements leading to software design that is

unstructured with logic that is difficult to decipher.

Without an automated tool, it is time-consuming to maintain Logic Flowcharts.

Logic Flowcharts may be used during detailed logic design to specify a module.

However, the presence of decision boxes may encourage the use of GoTo statements, resulting in

software that is not structured. For this reason, Logic Flowcharts may be better used during Structural

Design.

LIMITATIONS OF USING FLOWCHARTS

Complex logic: Sometimes, the program logic is quite complicated. In that case, flowchart becomes

complex and clumsy.

Alterations and Modifications:If alterations are required the flowchart may require re-drawing

completely.

Reproduction:As the flowchart symbols cannot be typed, reproduction of flowchart becomes a

problem.

The essentials of what is done can easily be lost in the technical details of how it is done.

GUIDELINES FOR DRAWING AFLOWCHART

a. In drawing a proper flowchart, all necessary requirements should be listed out in logical order.

b. The flowchart should be clear, neat and easy to follow. There should not be any room for ambiguity in

understanding the flowchart.

c. The usual direction of the flow of a procedure or system is from left to right or top to

bottom.

d. Only one flow line should come out from a process symbol.



23/46


e. Only one flow line should enter a decision symbol, but two or three flow lines, one for

each possible answer, should leave the decision symbol.

f. Only one flow line is used in conjunction with terminal symbol.

g. Write within standard symbols briefly. As necessary, you can use the annotation symbol to

describe data or computational steps more clearly.

h. If the flowchart becomes complex, it is better to use connector symbols to reduce the

number of flow lines. Avoid the intersection of flow lines if you want to make it more

effective and better way of communication.

i. Ensure that the flowchart has a logical start and finish.

j. It is useful to test the validity of the flowchart by passing through it with a simple test data.

Question No (15): Describe in detail about algorithm? Give example

Answer: An algorithm is a description of a procedure which terminates with a result. Simple algorithms

can be implemented within a function.

Properties of an algorithm

No ambiguity

There should not be any uncertainty about which instruction to execute next.

The algorithm should conclude after a finite number of steps.

The algorithm should be general.

Example:

Biggest among two numbers

Addition of N numbers

Finding Factorial of a number

Finding Fibonacci series.

Guidelines

Statements should be in simple English

Must produce a solution for the specified problem

It should be concise

Each instruction should be written in separate line and express one action.

Capitalize keywords such as READ, PRINT and so on.

Instruction should be written from top to bottom, with one entry and one exit.

Should allow easy transition from design to coding in programming language.

Benefits:

Language Independent.

Easy to develop a program from pseudo code than flowchart.

Easy to translate into programming language.


24/46


It is compact.

Limitations:

No visual representation of program logic

No accepted standards for writing pseudo codes.

Cannot be compiled or executed.

No real form or syntax rules.

Examples:

Finding a number is prime or not

QuestionNo(16): Define Operating System? What are functions and typesof operating System?

Answer: OPERATING SYSTEM: Operating System is a software that can be defined as:

An interface between users and hardware - an environment "architecture

Allows convenient usage; hides the tedious stuff

Allows efficient usage; parallel activity, avoids wasted cycles

Provides information protection

Gives each user a slice of the resources

Acts as a control program.

Functions ofoperating System:

An operting system manages hardware, runs applications, provides an interface for users, and

stores, retrieves, and manipulates files.

It manages the hardware and software resources of the system.

It provides a stable, consistent way for applications to deal with the hardware without having to

know all the details of the hardware.

System tool (programs) used to monitor computer performance,debug,problems, or maintainparts of the system.

A set of libraries or functions which may use to perform specific tasks especially relating to

interfacing with computer system components.

It avoids the situation of deadlock.

It is responsible for resource and performance optimization.

It manages process management and memory management


25/46

B.TECH-I SEM/FOC/THEORITICALNOTES ON UNIT-I AND II BY DHEERAJ MURARI Page 25

Types of Operating System

Type Definition Example ofUse

Batch Processing System Data or programs are

collected groupedand

processed at a laterdate.

Payroll, stockcontrol and

billing systems.

Real-time Systems Inputs immediately affectthe outputs.Timing is

critical

i.e. they are capable ofinfluencing the source of

the data e.g. control where

data from sensors is

processedimmediately and

affect the outputs -

controlling some device.

Timing is critical andthe

term real-time control

system.

e.g. control ofnuclear

power plants, oil refining,

chemical processing andair

traffic control systems.


26/46

B.TECH-I SEM/FOC/THEORITICALNOTES ON UNIT-I AND II BY DHEERAJ MURARI Page 26

Real-time transaction Inputs immediately affect

the outputsbut timing is

not critical.Each transaction iscompleted online as it arises

e.g. booking systems-eachbooking is online anda

database ofbookings canbe

amended interactively and

very quickly whilst another

user is locked out so

cannot double book or

alter that record at the same

time.

Holiday and airline

booking system.

Differencebetween real-

time and real-time

transactions. In real time,

time is criticlll anddelays

can be catastrophic but in

real-time transactions

systems there is no time

criticality. E.g. poor speeds

in airline control wouldbe

dangerous but poorbooking

speeds wouldnot be so

crucial.

Onlineprocessing Processingperformed

under the direct control ofthe CPU whilst the user

remains in communication

with the computer.

Offlineprocessing Processing which is doneaway from CPU.

e.g. hatching togetherof

clockcards,filling in OMR

forms.

Provides forinteraction

between the job and the

user,which may influencethe course of processing.

Wordprocessing

- ------


27/46


Question No(17): What are various Internal and External DOS Commands?

Answer: Internal Commands: The internal commands reside in COMMAND.COM, which loads into

memory when the computer system is started; these commands do not reside on disk. e.g.

(a) TIME- Displays current time and allows it to be changed.

Syntax: TIME

(b) DATE- Displays current date and allows it to be changed.Syntax: DATE

(c) CLS- Clears the screen.

Syntax: CLS


28/46

(d) DIR- Shows directory information of a diskette: name, size, and the date and time stamp of

files.

Syntax: DIR [d:][path]Optionalswitches:

/p Display dir info and pauses display when the screen is full

/w Display names and extensions only in five columns

To display a file directory listing for D:\LET\ANNUAL

D:\LET\ANNUAL>DIR (from D:\LET\ANNUAL)

D:\DATA>DIR \LET\ANNUAL (from D:\DATA)

C:\WINDOWS>DIR D:\LET\ANNUAL (from C:\WINDOWS)

(e) COPY- Copies a file. Name of copy may be the same as original, or different.

Syntax: COPY [d:][path][name.ext] [d:][path][name.ext]

Optionalswitches:

/v Verify, copies the file and compares it with the original

/b Binary file

To copy a file from D:\BATCH to the root of A: drive

A:\>COPY D:\BATCH\CL.BAT (from A: drive)

D:\BATCH>COPY CL.BAT A:\ (from D:\BATCH)

To copy a file from the root of C: to A: drive and change its name

A:\>COPY C:\MSDOS.SYS MSDOSSYS.BAK (from A:)

C:\>COPY MSDOS.SYS A:\MSDOSSYS.BAK (from the root of C:)

To copy all of the files from the root of A: to D:\CCV\ENGCOMP

A:\>COPY *.* D:\CCV\ENGCOMP (from A:)D:\CCV\ENGCOMP>COPY *.* A:\ (from D:\CCV\ENGCOMP)

(f) TYPE-Displays the contents of a file.

Syntax: TYPE [d:][path][name.ext]

To display the contents of the file MY.LET to the screen

A:\>TYPE MY.LET

(g) DEL- Deletes a file from disk.

Syntax: DEL [d:][path][name.ext]

To delete one file:

A:\>DEL A:\MY.LET

To del all files in current directory

A:\>DEL *.*

(h) REN- Renames a file.

Syntax: REN [d:][path][name.ext] [d:][path][newname.ext]

To change the name of the file D:\LET\ANNUAL\99.DOC to 1999.DOC



29/46

D:\LET>REN ANNUAL\99.DOC 1999.DOC (from D:\LET) D:\DATA>REN

\LET\ANNUAL\99.DOC 1999.DOC (from D:\DATA)

C:\WINDOWS>REN D:\LET\ANNUAL\99.DOC 1999.DOC (from C:\WINDOWS)

(i) MD- Makes (creates) a new directory.

Syntax: MD [d:][path][dirname]

To create a directory named HERMIT in the root of D: drive

D:\>MD HERMIT (from D:\)

C:\>MD D:\HERMIT (from C:\)

(j) RD- Removes an existing directory (directory must be empty).

Syntax: RD [d:][path][dirname]

To remove the HERMIT sub-directory

D:\>RD HERMIT (from D:\)

C:\>RD D:\HERMIT (from C:\)

(k) CD- Changes the current directory.

Syntax: CD [path][dirname]To make D:\HERMIT the current directory

D:\>CD HERMIT (from D:\)

D:\DATA>CD \HERMIT (from D:\DATA)

D:\DATA\SOURCE>CD \HERMIT (from D:\DATA\SOURCE)

D:\DATA\SOURCE>CD .. (from D:\DATA\SOURCE)

(l) PATH-The PATH command is used to help the command interpreter find external commands

which are not in the current directory. The command interpretter looks into the DOS

environment for "PATH=" and then searches the paths (each separated from the next by a

semicolon) that follow.

Syntax: PATH=[path;path;...]To set the DOS PATH:

PATH=C:\DOS;C:\PCW;\C:\BIN

To display the current path:

PATH

(m) SET PROMPT- Used to specify the appearance of the DOS prompt.

Syntax: SET PROMPT= (from the command line)

PROMPT= (in a batch file)

To display current drive & current path followed by ">" as prompt

SET PROMPT=$P$GTo display the current date, time, and drive on separate lines

SET PROMPT $D$_$T$_$N$G

To redefine F9 to CD\Windows\Start Menu\Programs\Startup

SET PROMPT $e[0,67;"'CD\Windows\Start Menu\Programs\Startup'";13p



30/46

External Commands:-The external commands are files that do reside on disk and have an extension of

.COM, .EXE, or .BAT. Both command types are executed from the MS-DOS prompt. Instructions for

external commands are disk-based. This means the file with the name of the command must be loaded

into RAM at the moment when the command is given. Application programs are external commands

and some DOS programs are external. The syntax for some of the more useful DOS external commands,

including their parameters and switches follow:

(a) FORMAT -Prepares a diskette for use by DOS.

Syntax: FORMAT [d:]

Parameters: [d:] = Drive which is to receive the format.

Optionalswitches:

/s Include all system files necessary to make disk "bootable"

/b Reserve space for system files on diskette. (Formats 320k instead of 360k).

/v Volume label of 11 characters

Someexamples:

To format a diskette in drive B: without system files: FORMAT B:

To format a diskette in drive A: with system files: FORMAT A: /s

To give the formatted diskette a volume name, include the /v switch: FORMAT A: /V

Combine switches to format a boot diskette with a volume label:FORMAT A: /S /V

(b) CHKDSK -Analyzes disk or diskette (first and only parameter) and displays disk and memory

status report.

Syntax: CHKDSK [d:] [/f] [/v]

Parameters: [d:] = Drive upon which to perform the checkdisk.

Optionalswitches:

/f Fix. Writes lost clusters to a disk file and corrects file allocation table.

/v Verbose. Lists all files on a disk.

Example:

To display statistics about the diskette in drive A: CHKSDK A:

To display statistics about the first hard disk and fix any lost clusters: CHKSDK A: /f

(c) DISKCOPY-Makes an exact copy of a diskette, including hidden system files if they are present.

Syntax: DISKCOPY [d1:] [d2:]Parameters:[d1:] = Drive for source diskette, [d2:] = Drive for target diskette.

Example: To make an exact copy of a diskette in drive A: to a diskette in B:DISKCOPY A: B:

To make an exact copy of a diskette using only drive A: DISKCOPY A: A:



31/46

DISKCOPY asks for a SOURCE diskette (the diskette being copied) and a TARGET diskette (the diskette

being copied to). The TARGET diskette need not be formatted, DOS will format it while doing the

DISKCOPY. If the SOURCE diskette is bootable, the system will be transferred to the TARGET as well. The

two disk drives must always use the same media.

Question No:(19): Explain Architecture of Unix? What are various Unix Commands?

Answer:- UNIXS is named after UNICS (UNiplexed Information and Computing Service). Its architecture

can be shown as below:

(1)UNIX Shell- Shell is an ordinary user program needs the ability to read from and write to the

terminal, and execute other programs, Commands may take arguments, which are passed to the

called program as character strings



32/46

Shell does not have to open terminal, but it has access automatically to a file standard input

(for reading), file standard output (for writing normal output), and file standard error (for

writing error messages)

Shell can redirect standard input/output to files

It can also use Pipe symbol

Example: grep ter *.t | sort >out

Possible pipeline sequence of pipe symbols

Single user can run several programs at once

Shell syntax for running a program in the background use &

Example: wc l b &

Shell scripts refers to the files containing shell command

UNIX Utility Programs- refers to standard application available with UNIX.

Large number of utility programs

Divided into six categories

D File and directory manipulation commands Example: cp a b | ls *.*

D Filters

Example: grep (extracts lines containing patterns), cut, paste,

D Program development tools such as editors/compilers

Example: cc (C compiler), make (maintain large programs whose source code

consists of multiple files)

D Text processing

Example: vi

D System administration

Example: mount (mount file system)

D Miscellaneous Example: kill 1325 (kill a process), chmod (change privileges of a file)



33/46

UNIX Kernel- is the heart of the operating system with following structure:

All UNIX drivers are classified as either character device drivers (mouse, keyboard) or blockdevice drivers (disk)

Network device drivers (possible character devices, but handled very differently)

Process dispatching when interrupt happens, context switch happens between processes

Editors such as vi/emacs need raw tty

Shell is line oriented, hence uses cooked mode and line disciplines



34/46

Networking software is layered with MAC/Routing/Transport layers and Socket interface

On top of buffer cache sits file system

Most UNIX systems support multiple file systems

Berkeley fast file system

Log-structured file system

Various System V file systems

On top of file system comes file naming, directory management, hard link and symbolic link

management, etc

On top page cache sits virtual memory (VM)

All paging logic is here, such as replacement algorithm

On top of VM is mapping files onto VM and high level page fault management code

Figure out what to do when a page fault occurs

On top of process dispatching is process management

Process scheduler to choose which process to run next

If threads are managed in the kernel, thread management is also here

Note in some UNIX systems, threads are managed in user space

On top of scheduling we have signal processing and process creation and termination

Top layer has the system call interface

All system calls are directed to one of the lower modules, depending on the nature of

the call

Top layer also has entrance to interrupts and traps Entrance to signals, page faults,

processor exceptions of all kinds, I/O interrupts

Various Commands OfUnix:-

Directories:File and directory paths in UNIX use the forward slash "/"

to separate directory names in a path.examples:

/ "root" directory

/usr directory usr (sub-directory of / "root" directory)

/usr/STRIM100 STRIM100 is a subdirectory of /usr

Moving around the file system:

pwd Show the "present working directory", or current directory.

cd Change current directory to your HOME directory.

cd .. Change current directory to the parent directory of the current directory.

cd $STRMWORK: Change current directory to the directory defined by the environment variable'STRMWORK'.

cd ~bob:Change the current directory to the user bob's home directory (if you have permission).

Listing directory contents:

ls list a directory



35/46

ls -l list a directory in long ( detailed ) format

for example:

$ ls -l

drwxr-xr-x 4 cliff user 1024 Jun 18 09:40 WAITRON_EARNINGS

-rw-r--r-- 1 cliff user 767392 Jun 6 14:28 scanlib.tar.gz

^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^

| | | | | | | | | | |

| | | | | owner group size date time name

| | | | number of links to file or directory contents

| | | permissions for world

| | permissions for members of group

| permissions for owner of file: r = read, w = write, x = execute -=no permission

type of file: - = normal file, d=directory, l = symbolic link, and others...

ls -a List the current directory including hidden files. Hidden files start

with "."

ls -ld * List all the file and directory names in the current directory using long format. Without the "d"option, ls would list the contents of any sub-directory of the current. With the "d" option, ls

just lists them like regular files.

Changing file permissions andattributes

chmod 755 file Changes the permissions of file to be rwx for the owner, and rx for the group and the

world. (7 = rwx = 111 binary. 5 = r-x = 101 binary)

chgrp user file Makes file belong to the group user.

chown cliff file Makes cliff the owner of file.

chown -R cliff dir Makes cliff the owner of dir and everything in its directory tree.

You must be the owner of the file/directory or be root before you can do any of these things.

Moving, renaming, and copying files:

cp file1 file2 copy a file

mv file1 newname move or rename a file

mv file1 ~/AAA/ move file1 into sub-directory AAA in your home directory.

rm file1 [file2 ...] remove or delete a file

rm -r dir1 [dir2...] recursively remove a directory and its contents BE CAREFUL!

mkdir dir1 [dir2...] create directories

mkdir -p dirpath create the directory dirpath, including all implied directories in the path.

rmdir dir1 [dir2...] remove an empty directory

Viewing and editing files:



36/46

cat filename Dump a file to the screen in ascii.

more filename Progressively dump a file to the screen: ENTER = one line down

SPACEBAR = page down q=quit

less filename Like more, but you can use Page-Up too. Not on all systems.

vi filename Edit a file using the vi editor. All UNIX systems will have

head filename Show the first few lines of a file.

head -n filename Show the first n lines of a file.

tail filename Show the last few lines of a file.

tail -n filename Show the last n lines of a file.

Shells :The behavior of the command line interface will differ slightly depending on the shell program

that is being used.Depending on the shell used, some extra behaviors can be quite nifty.You can find out

what shell you are using by the command:

echo $SHELL

Of course you can create a file with a list of shell commands and execute it like a program to perform atask. This is called a shell script. This is in fact the primary purpose of most shells, not the interactive

command line behavior.

Environment variables

You can teach your shell to remember things for later using environment variables.For example under

the bash shell:

export CASROOT=/usr/local/CAS3.0 Defines the variable CASROOT with the value

/usr/local/CAS3.0.

export LD_LIBRARY_PATH=$CASROOT/Linux/lib Defines the variable LD_LIBRARY_PATH with thevalue of CASROOT with /Linux/lib appended, or /usr/local/CAS3.0/Linux/lib

By prefixing $ to the variable name, you can evaluate it in any command:

cd $CASROOT Changes your present working directory to the value of CASROOT

echo $CASROOT Prints out the value of CASROOT, or /usr/local/CAS3.0

printenv CASROOT Does the same thing in bash and some other shells.

Interactive History: A feature of bash and tcsh (and sometimes others) you can use the up-arrow keys to

access your previous commands, edit

them, and re-execute them.

Redirection:



37/46

grep string filename > newfile Redirects the output of the above grep

command to a file 'newfile'.

grep string filename >> existfile Appends the output of the grep command to the end of 'existfile'.

The redirection directives, > and >> can be used on the output of most commands to direct their output

to a file.

Pipes:

The pipe symbol "|" is used to direct the output of one command to the input

of another.

For example:

ls -l | more This commands takes the output of the long format directory list command

"ls -l" and pipes it through the more command (also known as a filter).

In this case a very long list of files can be viewed a page at a time.

du -sc * | sort -n | tailThe command "du -sc" lists the sizes of all files and directories in the current

working directory. That is piped through "sort -n" which orders the output

from smallest to largest size. Finally, that output is piped through "tail" which

displays only the last few (which just happen to be the largest) results.

Command Substitution

You can use the output of one command as an input to another command in another way called

command substitution. Command substitution is invoked when by enclosing the substituted command

in backwards single quotes. For example:

cat `find . -name aaa.txt`

which will cat ( dump to the screen ) all the files named aaa.txt that exist in the current directory or in

any subdirectory tree.

Searching for strings in files: The grep command

grep string filename prints all the lines in a file that contain the string

Searching for files :The findcommand

find search_path -name filename

find . -name aaa.txt Finds all the files named aaa.txt in the current directory or

any subdirectory tree.

find / -name vimrc Find all the files named 'vimrc' anywhere on the system.

find /usr/local/games -name "*xpilot*"

Find all files whose names contain the string 'xpilot' which

exist within the '/usr/local/games' directory tree.



38/46

Reading and writing tapes, backups, and archives: Thetarcommand

The tar command stands for "tape archive". It is the "standard" way to read

and write archives (collections of files and whole directory trees).

Often you will find archives of stuff with names like stuff.tar, or stuff.tar.gz. This

is stuff in a tar archive, and stuff in a tar archive which has been compressed using the

gzip compression program respectivly.

Chances are that if someone gives you a tape written on a UNIX system, it will be in tar format,

and you will use tar (and your tape drive) to read it.

Likewise, if you want to write a tape to give to someone else, you should probably use

tar as well.

Tar examples:

tar xv Extracts (x) files from the default tape drive while listing (v = verbose)the file names to the screen.

tar tv Lists the files from the default tape device without extracting them.

tar cv file1 file2

Write files 'file1' and 'file2' to the default tape device.

tar cvf archive.tar file1 [file2...]

Create a tar archive as a file "archive.tar" containing file1,

file2...etc.

tar xvf archive.tar extract from the archive file

tar cvfz archive.tar.gz dname

Create a gzip compressed tar archive containing everything in the directory

'dname'. This does not work with all versions of tar.tar xvfz archive.tar.gz

Extract a gzip compressed tar archive. Does not work with all versions of tar.

tar cvfI archive.tar.bz2 dname

Create a bz2 compressed tar archive. Does not work with all versions of tar

File compression: compress,gzip, and bzip2

The standard UNIX compression commands are compress and uncompress. Compressed files have

a suffix .Z added to their name. For example:

compress part.igs Creates a compressed file part.igs.Z

uncompress part.igs Uncompresseis part.igs from the compressed file part.igs.Z. Note the .Z

is not required.

Another common compression utility is gzip (and gunzip). These are the GNU compress and

uncompress utilities. gzip usually gives better compression than standard compress,



39/46

but may not be installed on all systems. The suffix for gzipped files is .gz

gzip part.igs Creates a compressed file part.igs.gz

gunzip part.igs Extracts the original file from part.igs.gz

The bzip2 utility has (in general) even better compression than gzip, but at the cost of longer

times to compress and uncompress the files. It is not as common a utility as gzip, but is

becoming more generally available.

bzip2 part.igs Create a compressed Iges file part.igs.bz2

bunzip2 part.igs.bz2 Uncompress the compressed iges file.

Looking for help: The man andapropos commands

Most of the commands have a manual page which give sometimes useful, often more or less detailed,

sometimes cryptic and unfathomable descriptions of their usage. Some say they

are called man pages because they are only for real men.

Example:

man ls Shows the manual page for the ls command

You can search through the man pages using apropos

Example:

apropos build Shows a list of all the man pages whose descriptions contain the word "build"

Do a man apropos for detailed help on apropos.

Basics ofthe vieditor

Opening a file

vi filename

Creating text

Edit modes: These keys enter editing modes and type in the text

of your document.

i Insert before current cursor position

I Insert at beginning of current line

a Insert (append) after current cursor position



40/46

A Append to end of line

r Replace 1 character

R Replace mode

Terminate insertion or overwrite mode

Deletion of text

x Delete single character

dd Delete current line and put in buffer

ndd Delete n lines (n is a number) and put them in buffer

J Attaches the next line to the end of the current line (deletes carriage return).

Oops

u Undo last command

cut and paste

yy Yank current line into buffernyy Yank n lines into buffer

p Put the contents of the buffer after the current line

P Put the contents of the buffer before the current line

cursor positioning

^d Page down

^u Page up

:n Position cursor at line n

:$ Position cursor at end of file

^g Display current line number

h,j,k,l Left,Down,Up, and Right respectivly. Your arrow keys should also work ifif your keyboard mappings are anywhere near sane.

string substitution

:n1,n2:s/string1/string2/[g] Substitute string2 for string1 on lines

n1 to n2. If g is included (meaning global),

all instances of string1 on each line

are substituted. If g is not included,

only the first instance per matching line is

substituted.

^ matches start of line. matches any single character

$ matches end of line

These and other "special characters" (like the forward slash) can be "escaped" with \

i.e to match the string "/usr/STRIM100/SOFT" say "\/usr\/STRIM100\/SOFT"



41/46

Examples:

:1,$:s/dog/cat/g Substitute 'cat' for 'dog', every instance

for the entire file - lines 1 to $ (end of file)

:23,25:/frog/bird/ Substitute 'bird' for 'frog' on lines

23 through 25. Only the first instance

on each line is substituted.

Saving and quitting and other "ex" commands

These commands are all prefixed by pressing colon (:) and then entered in the lower

left corner of the window. They are called "ex" commands because they are commands

of the ex text editor - the precursor line editor to the screen editor

vi. You cannot enter an "ex" command when you are in an edit mode (typing text onto the screen)

Press to exit from an editing mode.

:w Write the current file.

:w new.file Write the file to the name 'new.file'.

:w! existing.file Overwrite an existing file with the file currently being edited.

:wq Write the file and quit.

:q Quit.

:q! Quit with no changes.

:e filename Open the file 'filename' for editing.

:set number Turns on line numbering:set nonumber Turns off line numbering

QuestionNo:(20) What are the characteristics of structure programming?

Answer:-Structured programming (sometimes known as modular programming) is a subset of

procedural programming that enforces a logical structure on the program being written to make it more

efficient and easier to understand and modify.

Certain languages such as Ada, Pascal, and dBASE are designed with features that encourage or enforce

a logical program structure.

Structured programming frequently employs a top-down design model, in which developers map out

the overall program structure into separate subsections. A defined function or set of similar functions is

coded in a separate module or submodule, which means that code can be loaded into memory

more efficiently and that modules can be reused in other programs. After a module has been tested

individually, it is then integrated with other modules into the overall program structure.



42/46

Program flow follows a simple hierarchical model that employs looping constructs such as "for,"

"repeat," and "while." Use of the "Go To" statement is discouraged.

Structured programming was first suggested by Corrado Bohm and Guiseppe Jacopini. The two

mathematicians demonstrated that any computer program can be written with just three structures:

decisions, sequences, and loops.

Question No:(21) What is Top-Down and bottom up approach of programming?

Answer:-Top-down and bottom-up are strategies of information processing and knowledge ordering,

mostly involving software, but also other humanistic and scientific theories. In practice, they can be seen

as a style of thinking and teaching. In many cases top-down is used as a synonym of analysis or

decomposition, and bottom-up of synthesis.

A top-down approach (also known as stepwise design) is essentially the breaking down of a system to

gain insight into its compositional sub-systems. In a top-down approach an overview of the system is

formulated, specifying but not detailing any first-level subsystems. Each subsystem is then refined in yet

greater detail, sometimes in many additional subsystem levels, until the entire specification is reducedto base elements. A top-down model is often specified with the assistance of "black boxes", these make

it easier to manipulate. However, black boxes may fail to elucidate elementary mechanisms or be

detailed enough to realistically validate the model.

A bottom-up approach is the piecing together of systems to give rise to grander systems, thus making

the original systems sub-systems of the emergent system. Bottom-up processing is a type of information

processing based on incoming data from the environment to form a perception. Information enters the

eyes in one direction (input), and is then turned into an image by the brain that can be interpreted and

recognized as a perception (output). In a bottom-

Documents

FOC Notes Unit 1 and Unit 2