if statement in c

One of the simplest ways to control program flow is by using if selection statements. Whether a block of code is to be executed or not to be executed can be decided by this statement.
The syntax for if selection statement in C could be as follows:

Syntax:

if(condition)
{
 statement(s); /*to be executed, on condition being true*/
}

If the conditional expression is true, the target of the if will be executed; otherwise, the target of the else, if it exists, will be executed. At no time will both be executed.
The conditional expression controlling the if may be any type of valid C expression that produces a true or false result.
If the Boolean expression evaluates to true, then the block of code inside the 'if' statement will be executed.
As a general rule, we express a condition using C's relational operators.
The relational operator allow us to compare two values to see whether they are equal to each other, unequal, or whether one is greater thanthe other.

this expression

is true if

x == y

x != y

x < y

x > y

x <= y

x >= y

x is equal to y

x is not equal to y

x is less than y

x is greater than y

x is less than or equal to y

x is greater than or equal to y

Fig- Flow Diagram of if statement

Example:

#include <stdio.h>
int main()
{
    int number;

    printf("Enter an integer: ");
    scanf("%d", &number);

    // Test expression is true if number is less than 0
    if (number < 0)
    {
        printf("You entered %d.", number);
    }
    printf("The if statement is easy.");
    return 0;
}

Output:

Enter an integer: -2
You entered -2.
The if statement is easy.