# Program Elements and Source Forms

A Fortran program consists of one or more program units. A program unit is usually a sequence of statements that define the data environment and the steps necessary to perform calculations; it is terminated by an END statement.

A keyword in a Fortran program can either be a part of the syntax of a statement (statement keyword), or it can be the name of a dummy argument (argument keyword).

Names identify entities within a Fortran program unit. In earlier versions of Fortran, names were called "symbolic names".

Character sets show the characters you can use in Fortran programs.

Fortran programs can be in free, fixed, or tab format.

For more information, see the individual topics in this section.

Parent topic: Language Reference

- Program Units
- Statements
- Keywords
- Names
- Character Sets
- Source Forms