C Program to Check Leap Year

In this article, you will learn and get code about checking any given year is a leap year or not. Before going to the program, here is the formula to check whether the given year is a leap year or not.

• Year that is divisible by 4 but not divisible by 100
• Or, Year that is divisible by 400

To understand, from where this formula came, then refer to Leap Year Formula Explained. Now let's move on and implement it in a C program.

Leap Year Program in C

Now I'm sure that you have complete understanding about what the leap year is and how it gets calculated. So its time to apply it in program:

#include<stdio.h>
#include<conio.h>
int main()
{
    int year;
    printf("Enter Year: ");
    scanf("%d", &year);
    if((year%4==0) && (year%100!=0))
        printf("\nIt's a Leap Year");
    else if(year%400==0)
        printf("\nIt's a Leap Year");
    else
        printf("\nIt's not a Leap Year");
    getch();
    return 0;
}

This program was compiled and executed using Code::Blocks IDE. Here is the first snapshot of sample run:

Supply any year say 2100 as input and press ENTER key to see the output as shown in the snapshot given below:

It is a very simple program, you can easily understand it as all the logic used behind leap year is described in the early of this article. So let's move on the another program using function.

Check Leap Year or Not in C using Function

This program continue checking for leap year, until user wants to terminate it. Because here, we have added some extra code, so that user becomes able to check leap year for any number time at one run only. To check leap year, this program uses function. Let's have a look at it:

#include<stdio.h>
#include<conio.h>
int checkLeapFun(int);
int main()
{
    int year, lORn;
    char choice='y';
    while(choice=='y')
    {
        printf("Enter Year: ");
        scanf("%d", &year);
        lORn = checkLeapFun(year);
        if(lORn == 0)
            printf("It's a Leap Year");
        else
            printf("It's not a Leap Year");
        printf("\n\nWant to check more ? (y/n): ");
        scanf(" %c", &choice);
        printf("\n");
    }
    getch();
    return 0;
}
int checkLeapFun(int yr)
{
    if((yr%4==0) && (yr%100!=0))
        return 0;
    else if(yr%400==0)
        return 0;
    else
        return 1;
}

Here is the sample run of above program:

In this way, you can continue checking until you want to terminate. To check for another year, just press y (for yes) and enter year. And to terminate it, just enter n (for no) or any other character except y.

Program Explained

• Declare any two variable of int (integer) type say year and lORn (leap or not)
• Here year holds year value entered by user, and lORn variable is used to get the return value of function checkLeapFun()
• Declare another variable say choice of char (character) type
• Initialize it with y as its value
• Here y is initialized as initial value of choice so to make the condition choice=='y' evaluates to be true (for first time), to enter into the while loop to process the code further
• Inside the loop, scan the year value from user, and pass it to the function checkLeapFun() with year as its parameter
• Now inside the function, apply the condition of leap year and return its value accordingly
• That is, if it is a leap year, then 0 gets returned, otherwise 1 gets returned and initialized to lORn variable
• After return statement, program flow come back inside the while loop of main() function, and the return value gets initialized to lORn as told in previous step
• Use if-else case to check and print the output according to the value of lORn
• Now scan a character from user, whether he/she want to check for another year or not
• If want to check for more, then press y otherwise press n
• Input character gets initialized to choice variable, and program flow goes to the condition of while loop
• Checks whether it is equal to y or not, if it is, the program flow goes inside the loop again, otherwise program flow terminates the loop and goes to the next statement written after the loop, that is gets();
• That's it

Note - Use space before scanning the character as input, because %c conversion specifier won't automatically skip any leading WhiteSpace. So, from previous entry, if there is a stray newline in input stream, the scanf() call will consume it immediately.

So here we have used:

scanf(" %c", &choice);

as statement of scanning a character. Because the blank, in the format string tells scanf to skip any leading whitespace.

Same Program in Other Languages

• C++ Check Leap Year
• Java Check Leap Year
• Python Check Leap Year

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