Printing leading 0's in C

printf("%05d", zipCode);

The 0 indicates what you are padding with and the 5 shows the width of the integer number.

Example 1: If you use "%02d" (useful for dates) this would only pad zeros for numbers in the ones column. E.g., 06 instead of 6.

Example 2: "%03d" would pad 2 zeros for one number in the ones column and pad 1 zero for a number in the tens column. E.g., number 7 padded to 007 and number 17 padded to 017.

The correct solution is to store the ZIP Code in the database as a STRING. Despite the fact that it may look like a number, it isn't. It's a code, where each part has meaning.

A number is a thing you do arithmetic on. A ZIP Code is not that.

You place a zero before the minimum field width:

printf("%05d", zipcode);