What is a checksum?
Q: What is a checksum?
A: A checksum is a number used as a redundancy check. It serves to verify that no errors have been made when writing down the number.
Q: How are checksums calculated?
A: Checksums can be calculated in different ways, but in its simplest form, the digits are simply added up. This however cannot detect errors of swapping digits around.
Q: What is an example of how checksums work?
A: Portuguese bank account identifiers are a good example of how checksums work. They have 21 digits and the last two digits represent the "mod 97" checksum based on modular arithmetic.
Q: How does this help detect errors?
A: If any digit is missed, swapped or written incorrectly, then the remainder would not be "1". In this case, the computer should detect an error and give an error message.
Q: Where else are checksums used?
A: Checksums are also used for serial numbers for computer software.
Q: What happens if there's an error detected by a checksum?
A: If there's an error detected by a checksum, then the computer should detect it and give an error message.
