Programming Tutorials

if, if...else and switch statements in C with samples

By: Siva in C Tutorials on 2008-08-06  

If ……….else statement:

The if..else statement is a two way branch: it means do one thing or the other. When it is executed, the condition is evaluated and if it has the value `true' (i.e. not zero) then statement1 is executed. If the condition is `false' (or zero) then statement2 is executed. The if..else construction often saves an unnecessary test from having to be made.

if (condition)
{
statements
}
else
{
statements
}

Example:

/*-------------------------------------------------------*/
/* To find whether a given year is leap or not */
/*-------------------------------------------------------*/

main()
{
    int y, r1, r2;
    printf("Enter a year");
    scanf("% d", &y);
    r1 = y % 4;
    if (r1 = = 0)
    {
        r2 = y % 100;
        if (r2 = = 0)
            printf("The given year is not a leap year");
        else
            printf("The given year is a leap year");
    }
    else
        printf("The given year is not a leap year");
}

Logical Operators:

Comparisons are often made in pairs or even in groups and linked together with words like OR and AND. The following are the logical operators in C:

1. || [logical OR]
2. & & [logical AND]
3. ! [logical NOT]

[ || ]OR Logical Operator

Condition-I Condition-II Result
----------- ----------- ---------
True	False	True
False	True	True
False	False	False
True	True	True

[& &]AND Logical Operator

Condition-I Condition-II Result
---------- ------------ ---------
True	False	False
False	True	False
False	False	False
True	True	True

[!] NOT Logical Operator

!(True) => False

!(false) => True

Example:

/*--------------------------------------------------------------------------------------------*/
/* To check whether a given alphabet is capital or not (using logical operator) */
/*--------------------------------------------------------------------------------------------*/

main()
{
    char x;
    printf("Enter an alphabet");
    scanf("%c", &x);

    if (x >= 65 && x <= 90)
        printf("The given alphabet is capital");
    else
        printf("The given alphabet is not capital");
}

Switch Statement:

The switch statement is another way of making a program path branch into lots of different limbs. The switch statement has the following form:

switch (integer value or constant value)

{

case 1: statement1;

break; /* optional line */

case 2: statement2;

break; /* optional line */

....

default: default statement

break; /* optional line */

}

Example:

/* Input a direction code and print the direction name(using switch)*/

main()
{
    char y;
    clrscr();
    printf("Enter the code");
    scanf("%c", &y);
    switch (y)
    {
    case 'N':
        printf("North Direction");
        break;
    case 'S':
        printf("South Direction");
        break;
    case 'E':
        printf("East Direction");
        break;
    default:
        printf("West Direction");
        break;
    }
}