Using Decision Making Statements, if and if-else in C program

When you are writing C program, sometimes you need to make certain checks on variables and based on which you need to take some decisions.. this is called as Decision making statements in C programming Language.

In this post, we will show you how you can use simple conditional statements “if” and “if-else” in your C programs

C programming supports following conditional operators

x == y means “returns true if x is equals to y” otherwise “return false”
x != y means “returns true if x is not equals to y” otherwise “return false”
x < y means “returns true if x is less than y” otherwise “return false”
x > y means “returns true if x is greater than y” otherwise “return false”
x <= y means “returns true if x is less than or equals to y” otherwise “return false”
x >= y means “returns true if x is greater than or equals to y” otherwise “return false”

Now, lets use above conditional operators to show how you can use if and if-else to execute different code based on this conditions.

Using IF

$ vim if.c

#include <stdio.h>

int main (int argc, char **argv) {
int x = 10, y = 22 ;

if (x <= y)
    printf ("x is less than or equal to y");

return 0;
}

Notice in above code, how we have written the “if” statement.

we need to add open and close bracket () in for the condition check
We can start the next line after “if” at any place

if we execute this C code, now on console.. we can see that it will print the string “x is less than or equal to y” as x is set to 10 and y is set to 22.

$ gcc -o if_bin if.c

$ ./if_bin 
x is less than or equal to y

Using IF-ELSE

$ vim ifelse.c

#include <stdio.h>

int main(int argc, char **argv) {
    int x = 10, y = 22 ;

    if (x <= y)
        print ("x is less than or equal to y");
    else 
        print ("x is greater than y");

    return 0;
}

As we have checked in “if’ when x = 10 and y = 22 i.e. 10 < 22, the code’s if statement “x <= y” will become true and “x is less than or equal to y” message will get printed.

Now, lets change values of x = 22 and y = 10 as below,

#include <stdio.h>

int main(int argc, char **argv) {
int x = 22, y = 10 ;

if (x <= y)
    print ("x is less than or equal to y");
else 
    print ("x is greater than y");

return 0;
}

and now if we run this code, since 22 > 10 i.e. x > y , the first “if x <= y” returns false, hence code execution will go to “else”
and if will print “x is greater than y”

$ gcc -o ifelse_bin ifelse.c

$ ./ifelse_bin
x is greater than y

Using IF

Using IF-ELSE

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