A program is presented to determine if a given year is a leap year or not. The program takes a year as input, calls the leap_year function passing the year, and the function returns 1 if it's a leap year or 0 if it's not. The function checks if the year is divisible by 4, then if it's also divisible by 100 it's not a leap year, unless it's also divisible by 400, in which case it is a leap year.