<Dt> File existence check </Dt> <Dd> Checks that a file with a specified name exists . This check is essential for programs that use file handling . </Dd> <Dl> <Dt> Format or picture check </Dt> <Dd> Checks that the data is in a specified format (template), e.g., dates have to be in the format DD / MM / YYYY . Regular expressions should be considered for this type of validation . </Dd> </Dl> <Dt> Format or picture check </Dt>

How is validation done in a spreadsheet what are the types of validation possible