FORTRAN Reference Manual

Language Elements
FORTRAN Reference Manual—528615-001
2-7
Scope of Symbolic Names
Scope of Symbolic Names
The scope of a symbolic name is the range within which the symbolic name is defined:
a name’s scope can be an executable program, a program unit, a statement function
statement, or an implied DO list in a DATA statement.
•
The name of the main program and the names of block data subprograms,
external functions, subroutines, and common blocks have the scope of an
executable program.
•
The names of variables, arrays, RECORDs, RECORD fields, constants, statement
functions, intrinsic functions, and dummy procedures have the scope of a program
unit.
•
The names of variables that appear as dummy arguments in a statement function
statement have the scope of that statement.
•
The names of variables that appear as the DO variable of an implied DO in a DATA
statement have the scope of the implied DO list.
No two entities in the same scope can have the same symbolic name, except that a
common block name can be the same as a program unit name.
If you use the name of a FORTRAN intrinsic function as a symbolic name, all
references to that name within the program unit that declares the symbolic name
reference your identifier name. You cannot invoke the intrinsic function from that
program unit.
Avoid using FORTRAN keywords as symbolic names. Although the FORTRAN
compiler does not report a warning or an error if you use a keyword as a symbolic
name, your program is less readable.
Data Types
Every variable, array, RECORD field, symbolic constant, statement function, and
function name has a type. FORTRAN recognizes the following data types:
•
Integer
•
Real
•
Double precision
•
Complex
•
Logical
•
Character
The symbolic name of a main program, subroutine, common block, or block data
subprogram does not have a data type.