The INPUTNULL statement allows the definition of a character that will allow a null input to be seen by the [email protected] statement.
The expression should evaluate to a single character. Subsequently, any [email protected] statement that sees only this character input before the new-line sequence will NULL the variable in which input is being stored.
If expression evaluates to the NULL string " then the default character of _ is used to define a NULL input sequence.
The INPUT statement does not default to accepting the _ character as a NULL input, the programmer must explicitly allow this with the statement: