### C program to check if a year is leap year or not :

To check if a year is *leap year or not*, we need to check if it is *divisible by 4 or not*. A year is *leap year* if it is divisible by *4* and for century years, if it *also divisible by 400*. In this example, we will learn how to check if a year is leap year or not in *C programming language*. Let’s take a look into the *algorithm* first :

### Algorithm to check if a year is leap year or not :

- Check if it is
*divisible by 4*. If not than it is*not a leap year*. - If
*divisible by 4*, check if it is*divisible by 100*. If not , it is not a century year, so it*is a leap year*. - If divisible by 100, check
*if it is divisible by 400 or not*. If yes*it is a leap year*, else not.

List of leap years from *1900* to *2020* are : *1904, 1908, 1912, 1916, 1920, 1924, 1928, 1932, 1936, 1940, 1944, 1948, 1952, 1956, 1960, 1964, 1968, 1972, 1976, 1980, 1984, 1988, 1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020 .*
Let’s take a look into the program :

```
#include <stdio.h>
#define LEAP_YEAR 1
#define NON_LEAP_YEAR 0
int checkLeapYear(int year)
{
if (year % 4 == 0)
{
if (year % 100 == 0)
{
if (year % 400 == 0)
{
return LEAP_YEAR;
}
else
{
return NON_LEAP_YEAR;
}
}
else
{
return LEAP_YEAR;
}
}
else
{
return NON_LEAP_YEAR;
}
}
int main()
{
int year;
printf("Enter a year to check : \n");
scanf("%d", &year);
if (checkLeapYear(year) == LEAP_YEAR)
{
printf("Entered year is a leap year.");
}
else
{
printf("Entered year is not a leap year.");
}
return 0;
}
```

We can also simplify the *checkLeapYear* function as below :

```
#include <stdio.h>
#define LEAP_YEAR 1
#define NON_LEAP_YEAR 0
int checkLeapYear(int year)
{
if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0))
{
return LEAP_YEAR;
}
else
{
return NON_LEAP_YEAR;
}
}
int main()
{
int year;
printf("Enter a year to check : \n");
scanf("%d", &year);
if (checkLeapYear(year) == LEAP_YEAR)
{
printf("Entered year is a leap year.");
}
else
{
printf("Entered year is not a leap year.");
}
return 0;
}
```

### Sample Output :

```
Enter a year to check :
2018
Entered year is not a leap year.
Enter a year to check :
1984
Entered year is a leap year.
Enter a year to check :
2000
Entered year is a leap year.
```

The output is same for both of these program.