Course: BSC CS

Subject: Programming In C Language

Unit-1

Introduction to C language

Function OF Computer

Input -- Input devices enable us to get information into a computer. Some examples include a keyboard, mouse, microphone, scanner, or digital camera.

Storage -- There are two types of storage: temporary and long-term.

RAM, or random access memory, is temporary, meaning it stores information as you use it, but it is being constantly erased and rewritten as you open and close files. Long-term storage holds information for as long as you want it. Hard drives, portable hard drives, floppy drives, flash drives, CD’s, and DVD’s are long term storage devices.

Processor -- A microprocessor controls the computers’ functions. It is smaller than a dime, but contains millions of transistors that perform millions of instructions per second. The microprocessor performs these instructions using a three-step process: fetch, decode and execute.

Output -- Information that has been processed is communicated back to the user in the form of words, sounds or pictures, and is delivered through printers, speakers, monitors or other output devices. Sometimes output is just written back to a storage dev

Basic Building Block Of Computer

Control Unit- this is the device or a part of computer responsible or performs such regulating functions..Arithmetic Logic Unit- this is the part or a circuitry of the Microprocessor chip for arithmetic operations, proportional and related functions, and logical functions. Memory- this is a part of computer or a card or modules that inserted to the motherboard’s slotInput -The System Unit that the system of computer feeds or decode first the data before to display using the output devices of computer.Output Devices- this is refer to the devices of computer that have an ability to display the information or can produce a hardcopy of a document.

Computer Applications

Classification Of Computer

Classification Of Programming Language

What is UNIX?

UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.

UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment.

However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.

Cont..

There are many different versions of UNIX, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X.

What is LINUX?

It is the software on a computer that enables applications and the computer operator to access the devices on the computer to perform desired functions.

Linux is developed collaboratively, meaning no one company is solely responsible for its development or ongoing support. Companies participating in the Linux economy share research and development costs with their partners and competitors

WindowsThe operating system gives the framework upon

which all other services and applications run. The majority of home users use a Windows based machine. Most of today’s applications and games are designed to run solely on Microsoft systems.

Microsoft Windows is extremely popular in schools and colleges, many businesses also use Windows.

The oldest of all Microsoft’s operating systems is MS-DOS (Microsoft Disk Operating System). MS-DOS is a text-based operating system. Users have to type commands rather than use the more friendly graphical user interfaces (GUI’s)available today

What is algorithm?

A method that can be used by a computer for the solution of a problem.

A sequence of computational steps that transform the input into the output.

The word ”algorithm” comes from the name of a Persian author, Abu Ja’far Mohammed ibn Musa al Khowarizmi (c. 825 A.D.), who wrote a textbook on mathematics.

An algorithm (pronounced AL-go-rith-um) is a procedure or formula for solving a problem. 

Algorithm

Write an algorithm and draw the flowchart for finding the average of two numbers Algorithm:

Input: two numbers x and yOutput: the average of x and ySteps: input xinput ysum = x + yaverage = sum /2output average

Introduction to flowchartsA flowchart is a graphical representation of an

algorithm.

• Start or end of the program  

• Computational steps or processing function of a program    

• Input or output operation    

• Decision making and branching    

• Connector or joining of two parts of program

Introduction of ‘C’

Root of the morden language is ALGOL 1960. It’s first computer language to use a block structure.

It gave concept of structured programming.

In 1967, Martin Richards developed a language, BCPL (Basic Combined Programming Language)

In 1970,by Ken Thompson created a language called as ‘B’.

It used to create early version of Unix.

In 1972,by Dennis Ritchie introduced new language called as ‘C’ .

1972 Traditional C Dennis Ritchie

1990 ANSI/ISO C ISO Committee

1978 K&R C Kernighan &Ritchie

1989 ANSI C ANSI Committee

Features Of C It is robust lang whose rich setup of built in functions and operator can be used to write

any complex prog

Prog written in c are efficient due to severals variety of data types and powerful operators. The c complier combines the capabilities of an assembly lang with the feature of high

level language. Therefore it is well suited for writing both system software and business package.

There r only 32 keywords, severals standard functions r available which can be used for developing prog.

c is portable lang , this means that c programes written for one computer system can be run on another system, with little or no modification.

c lang is well suited for stuctured programming, this requires user to think of a problems in terms of function or modules or block. A collection of these modules make a program debugging and testing easier.

c language has its ability to extend itself. A c program is basically a collection of functions that are supported by the c library. We can contuniously add our own functions to the library with the avaibility of the large number of functions.

In india and abroad mostly people use c programming lang becoz it is easy to learn and understand

  Basic structure of C programming  To write a C program, we first create functions and then put them together. A C program

may contain one or more sections. They are illustrated below.

Documentation section Link section Definition section Global declaration section main () Function section { Declaration part Executable part          

} Subprogram section Function 1 Function 2 ………….. ………….. Function n (User defined functions)

Basic structure of ‘C’

Documentation Section It has set of comment lines(name of program, author

details).

What is Comment line?? To guide a programmer to write a note for

function,operation,logic in between a program. Non-executable statement. Can’t be nested.

e.g:- /* Hello /* abc */ Hi */ ERROR.

Link Section It provides instructions to the compiler to link

function from the system library.

# include Directive:-

To access the functions which are stored in the library, it is necessary to tell the compiler , about the file to be accessed.

Syntax:- #include<stdio.h>

stdio.h is header file.

Definition Section

defines all symbolic constants.#define instruction defines value to a symbolic

constant.

#define:-

It is a preprocessor compiler directive, not a statement.

Therefore it should not end with a semicolon. Generally written in uppercase.

Global Declaration Section

Some variables that are used in more than on function, such variables (global variables) declared in the global declaration section.

It also declares all the user-defined function.

Every ‘C’ program must have one main() function section.

It contains two parts

1) Declaration part: It declares all variables used in the executable part.

2) Executable part: It has atleast one statement.

Main() function section

A simple C program: Printing a line of text

#include <stdio.h>main(){ printf(“hello, world\n”);}

Program output:hello, world

Executing a C program :

  Executing a C program involves a series of steps. They are,

 Creating the program.Compiling the program.Linking the program with functions that are

needed from the C library.  Executing the program.

How to run a program?

There are two ways to run programs written in a high-level language.

The most common is to Compile the program

The other method is to pass the program through an interpreter.

Compiler

Why compiler is require ?

As machine (a processor) can operate On binary code instruction only…..If we use higher level language then …For execution of the program we must Convert it to lower level / machine levelCode.

Means,

A program that translates Source code into object code.

The compiler derives its name from the way it works, looking at the entire piece of source code and collecting and reorganizing the instructions.

Interpreter:

which analyzes and executes each line of source code without looking at the entire program.

Advantage of interpreter:

It can execute a program immediately. Compilers require some time before an executable program emerges.But,However, programs produced by compilers Run much faster than the same programs executed by an interpreter.

Compiler

checks for syntax errors if any on success coverts ‘C source code into object code form which is nearer to machine…

process of compiling and running a C program

References:

1.  Programming in C by yashwant kanitkar

2. ANSI C by E.balagurusamy- TMG publication

3. Computer programming and Utilization by sanjay shah Mahajan Publication

4. .www.cprogramming.com/books.html5. en.wikipedia.org/wiki/C_(programming_language)6. www.programmingsimplified.com/c-program-example7. http://cm.bell-labs.com/cm/cs/who/dmr/chist.html

8. http://en.wikipedia.org/wiki/Comparison_of_programming_languages

9. http://en.wikipedia.org/wiki/List_of_C-based_programming_languages

10. http://en.wikipedia.org/wiki/C_(programming_language)