This C program displays the day of the week for any year, month, day entered in the screen. Instead of a month table, it uses the same formula as the calendar program also presented by this web site.

The Weekday Routine converts year, month, day into a subscript representing the day of the week.

The Weekday Table is indexed by the subscript to return the character string of the weekday name.

The String Loader routine retrieves the year, month, and day from the screen as character strings.

The Alpha-to-Integer routine converts the strings to integers.

The Main Routine where execution begins, gives an example of defining both the largest and smallest possible integers using bitwise operators.