A file variable is a variable that can be assigned file values. A file variable can be given a value by receiving a file constant passed as an argument, by receiving a file constant as the value of a function, or by simple assignment. A file variable is declared with the VARIABLE attribute. For example:
DECLARE G FILE; DECLARE F FILE; DECLARE V FILE VARIABLE; V=F; ... V=G;
In this example, F and G are file constants, each of which has an associated file control block. V is a file variable that can be assigned file values. After the first assignment, both F and V designate the same file control block. Any operation performed on V is equivalent to the same operation performed on F. After the second assignment, any operation performed on V is equivalent to the same operation performed on G, because both V and G designate the same file control block.
A file name used as a parameter is a file variable and designates the same file control block as its corresponding argument.