Specify a full procedural file (F in position 18 of the
fixed-form file description
specifications, or any file defined by a free-form file definition) to control all or partial input of a program. A full
procedural file indicates that input is controlled
by program-specified calculation operations (for example, READ, CHAIN).
When both full procedural files and a primary file (P in position
18 of the file description specifications) are specified in a program,
some of the input is controlled by the program, and other input is
controlled by the cycle. Even if the program cycle exists in your
module, all the processing of a full-procedural file is done in your
calculations.
The file operation codes can be used for program control of input. These file operation codes are discussed in File Operations.

