Variable in C

Variable in C

Introduction:

When a person sits in a chair then it takes some physical space. Like that in a programming concept when a variable is declared it takes some logical memory space . So we can say that a variable is a memory location which is used to store some data values. Someone can also say that a variable is a place holder because it holds some memory. At different times during program execution, a variable can take different data values. But at a single time the variable cannot take many values instead of single values. A variable name should be given by the programmer in such a way that it is easy to execute the program.

Tips to remember: Try to choose a simple variable name .So that it easy to perform the operation/implementation.

Declaration of variable:

The declaration of a variable consist of two parts, i.e., one is data types and other is variable name. Data types determine what types of data values the variable will hold. It may determine integer type values, float type, char type or double type values. The variable name means the programmer has given the name of the variable which should be simple. The declaration of a variable is necessary because it can be used later in a program.

The syntax of declaring a single variable is:

data-type variable_name;

The syntax of multiple variable in one statement is:

data-type variable1, variable2  ________ variablen-n;

Initialization of variable:

When a programmer declares the variable it automatically assigns the undefined values. The undefined values may be positive or negative integer values depending on the computer and which are called garbage values or uninitialized values. When the programmer assigns some values to that variable then it is called initialization of variables. So initialization of variable means giving values to variable.

The syntax of initialization of variable is:

data-type variable_name=constants;

Rules of naming a variable:

The programmer cannot give any name to the variable. The name of the variable follows some specific rules and regulations followed by C compiler. The variable name is the combination of letters, digits, and underscores, character according to specific conditions.

The conditions are,

1. The variable name can begin with underscore(_), letter(it may be a lower case letter or upper case letter).    Examples:_Total; or Total; or total; or TOTAL; 2. The length of a variable should not exceed 31 characters. But many compilers allowed normally maximum eight characters. 3. The variable names are case sensitive, i.e., upper case and lower case alphabets are different, e.g., number is not same as NUMBER. 4. Keywords are not allowed, e.g., for, if, while, do while. Example: Wrong: int for; Correct: int student_id; 5. While space/blank spaces are not allowed. Example: Wrong: int student id; Correct is: int student_id; 6. Special characters e.g. %, $, #,@ are not allowed. Example: Wrong: int #student_id; Correct is: int student_id;

Example:

A program to add two number in C.

#include <stdio.h>

#include <conio.h>

void main ()

{

clrscr ();

int a, b, sum;

printf (“ Enter a number a”);

scanf (“%d”,&a);

printf (“ Enter a number b”);

scanf (“%d”,&b);

sum = a+b;

printf (“ Sum of two number is %d”,sum);

getch();

}

OUTPUT

Enter a number a 3

Enter a number b 4

sum of two number is 7