A Quick Look to C-programming Concepts

1.0 OVERVIEW OF C PROGRAMMING

• C language is one of the most popular computer languages today because it is a structured,high level, machine independent language. 
•  C is called a high level,compiler language. The aim of any high level computer language is to provide an easy and natural way of giving a programme of instructions to a computer.
• C is one of a large number of high level languages which can be used for general purpose programming, i.e., anything from writing small programs for personal amusement to writing complex applications.
• C allows meaningful variable names and meaningful function names to be used in programs without any loss of efficiency and it gives a complete freedom of style, it has a set of very flexible loop constructions and neat ways of making decisions. 
• Another feature of C is the way it can express ideas concisely.
•  The richness of a language shapes what it can talk about. C gives us the apparatus to build neat and compact programs.
• C tries to make the best of a computer by linking as closely as possible to the local environment.
• The C compiler combines the capabilities of an assembly language with the features of a high-level language and therefore it is well suited for writing both system software and business packages.
• Programs written in C are efficient and fast. 
• This is due to its variety of data types and powerful operators. 
• C is highly portable. This means that C programs written for one computer can be run on another with little or no modification. Another feature of C is its ability to extend itself.

1.1 INTRODUCTION

C is a remarkable language. Designed originally by Dennis Ritchie, working at AT&T Bell

Laboratories in New Jersey, it has increased in use until now it may well be one of the most widely-

written computer languages in the world. C is a structured language. It allows variety of programs

in small modules. It is easy for debugging, testing, and maintenance if a language is a structured

one.

1.2 STRUCTURE OF A C PROGRAM

Include header file section

Global declaration section

main()

{

Declaration part

Executable part

}

User-defined functions

{

Statements

}

Include Header File Section           

C program depends upon some header files for function definition that are used in program.

Each header file by default is extended with .h. The header file should be included using # include

directive as given here.

Global Declaration

This section declares some variables that are used in more than one function. These variables

are known as global variables. This section must be declared outside of all the functions.

Function Main

Every program written in C language must contain main () function. The function main() is

a starting point of every C program. The execution of the program always begins with the function

main ().

Declaration Part

The declaration part declares the entire variables that are used in executable part. The

initialisations of variables are also done in this section. Initialisation means providing initial value

to the variables.

Executable Part

This part contains the statements following the declaration of the variables. This part conatins

a set of statements or a single statement. These statements are enclosed between the braces.

User Defined Function

The functions defined by the user are called user-defined functions. These functions are

generally defined after the main () function.

1.3 STEPS FOR EXECUTING THE PROGRAM

1. Creation of program 

  Programs should be written in C editor. The file name does not necessarily include extension

C. The default extension is C.

2. Compilation of a program

The source program statements should be translated into object programs which is suitable

for execution by the computer. The translation is done after correcting each statement. If

there is no error, compilation proceeds and translated program are stored in another file

with the same file name with extension “.obj”.

3. Execution of the program

After the compilation the executable object code will be loaded in the computers main

memory and the program is executed.

1.7 IDENTIFIERS

Identifiers are names of variables, functions, and arrays. They are user-defined names,
consisting sequence of letters and digits, with the letter as the first character.

1.8 CONSTANTS

Values do not change during the execution of the program
Types:

1. Numerical constants:

— Integer constants
These are the sequence of numbers from 0 to 9 without decimal points or fractional
part or any other symbols. It requires minimum two bytes and maximum four bytes.
Eg: 10,20, + 30, – 14
— Real constants
It is also known as floating point constants.
Eg: 2.5, 5.342

2. Character constants:

— Single character constants
A character constant is a single character. Characters are also represented with a
single digit or a single special symbol or white space enclosed within a pair of single
quote marks
Eg: ‘a’, ‘8’, “ ”.
— String constants
String constants are sequence of characters enclosed within double quote marks.
Eg: “Hello”, “india”, “444”

Want to learn more then please click on ==>>Next