# I/O Formatting

A format appearing in an input or output (I/O) statement specifies the form of data being transferred and the data conversion (editing) required to achieve that form. The format specified can be explicit or implicit.

Explicit format is indicated in a format specification that appears in a FORMAT statement or a character expression (the expression must evaluate to a valid format specification).

The format specification contains edit descriptors, which can be data edit descriptors, control edit descriptors, or string edit descriptors.

Implicit format is determined by the processor and is specified using list-directed or namelist formatting.

List-directed formatting is specified with an asterisk (*); namelist formatting is specified with a namelist group name.

List-directed formatting can be specified for advancing sequential files and internal files. Namelist formatting can be specified only for advancing sequential files.

Parent topic: Language Reference

- Format Specifications
- Data Edit Descriptors
- Control Edit Descriptors
- Character String Edit Descriptors
- Nested and Group Repeat Specifications
- Variable Format Expressions
- Print Formatted Records
- Interaction Between Format Specifications and I/O Lists

## See Also

Rules for List-Directed Sequential READ Statements for details on list-directed input
Rules for List-Directed Sequential WRITE Statements for details on list-directed output
Rules for Namelist Sequential READ Statements for details on namelist input
Rules for Namelist Sequential WRITE Statements for details on namelist output