Table of Contents
Conditional statements are often used in programming to make decisions. In the chapter you will learn how to makes decisions using if conditional statements in C programming.
C Programming IF Statement
There are three types if conditional statement in C programming:
1. if-if 2. if…else-if…else 3. if…elseif…else-if…elseif…else
C IF Statement Syntax
if (testExpression)
{
// This code will execute.
}
Here if first evaluetes test Expression.
If test Expression is True (not null) then if the statement/statements inside the block will be executed.
If test Expression is False (null), if the statement/statements within the block will be skipped.
Wen the value of test Expression is True and when it is False is discussed in our relational and logical operators page.
Example: C if Statement
// Program to display positive numbers on screen when user inputs them.
//User input negative number will not be displayed on the screen.
#include <stdio.h>
int main()
{
int testNumber;
printf("Enter an unsigned integer: ");
scanf("%d", &testNumber);
//If the value of testNumber is greater than 0 then the Test expression will be True.
if (testNumber > 0)
{
printf("You have entered %d.\n",testNumber);
}
printf("The if statement is easy in C programming.");
return 0;
}
Enter an unsigned integer: 5
You entered 5.
The if statement is easy in C programming.
(testNumber > 0) The test expression return True when the user enters 5. S your entered 5 will be displayed.
Enter an integer: -6
The if statement is easy in C programming.
(testNumber < 0) The test expression returns False when the user enters -6. So the compiler if skips the statement inside it.
Here is another example to better understand the if statement:
#include <stdio.h>
int main()
{
int i;
/* this is always true */
if (1) {
printf ("This should be printed.\n");
}
/* This is never true */
if (0) {
printf ("This should not be printed.\n");
}
/* we can also use "else" */
if (0) {
printf ("This should not be printed.\n");
}
else {
printf ("This 'else' part should be printed\n");
}
i = 1;
/* One can optionally not use { and } when there is only one statement. */
if (i == 1){
printf ("This is a branch without the braces { and }.\n");
}
/* be careful about the equal(=) sign? */
if (i = 100){
printf ("Beware of equal signs in if statements.\n");
}
return 0;
}
This should be printed.
This 'else' part should be printed.
This is a branch without the braces { and }.
Beware of equals signs in if statements.
