Declarations for Character Types

A CHARACTER type specifier can be immediately followed by the length of the character object or function. It takes one of the following forms:

Keyword Forms

CHARACTER [([LEN=]len)]

CHARACTER [([LEN=]len [, [KIND=]n])]

CHARACTER [(KIND=n [, LEN=len])]

Nonkeyword Form

CHARACTER*len[,]

len

Is a length type parameter. It can have one of the following values:

A scalar integer expression
*
:

The following rules also apply:

In keyword forms

The len is a specification expression, an asterisk (*), or a colon (:). If no length is specified, the default length is 1.

If the length evaluates to a negative value, the length of the character entity is zero.
In nonkeyword form

The len is a specification expression or an asterisk enclosed in parentheses, or a scalar integer literal constant (with no kind parameter). The comma is permitted only if no double colon (::) appears in the type declaration statement.

This form can also (optionally) be specified following the name of the data object or function (v*len). In this case, the length specified overrides any length following the CHARACTER type specifier.

The largest valid value for len in both forms is 2**31-1 on IA-32 architecture; 2**63-1 on Intel® 64 architecture. Negative values are treated as zero.

n

Is a scalar integer initialization expression specifying a valid kind parameter. Currently the only kind available is 1.

Description

An automatic object can appear in a character declaration. The object cannot be a dummy argument, and its length must be declared with a specification expression that is not a constant expression.

The length specified for a character-valued statement function or statement function dummy argument of type character must be an integer constant expression.

When an asterisk length specification *(*) is used for a function name or dummy argument, it assumes the length of the corresponding function reference or actual argument. Similarly, when an asterisk length specification is used for a named constant, the name assumes the length of the actual constant it represents. For example, STRING assumes a 9-byte length in the following statements:

  CHARACTER*(*) STRING

  PARAMETER (STRING = 'VALUE IS:')

A function name must not be declared with a * length unless it is of type CHARACTER and is the name of the result of an external function or the name of a dummy function.

A function name declared with a * length must not be an array, a pointer, recursive, elemental, or pure.

If the CHARACTER type declaration statement specifies a colon (:) length, the length type parameter is a deferred type parameter. An entity or component with a deferred type parameter must specify the ALLOCATABLE or POINTER attribute. A deferred type parameter is a length type parameter whose value can change during execution of the program.

The form CHARACTER*(*) is an obsolescent feature in Fortran 95.

Examples

In the following example, the character string last_name is given a length of 20:

  CHARACTER (LEN=20) last_name

In the following example, stri is given a length of 12, while the other two variables retain a length of 8.

  CHARACTER *8 strg, strh, stri*12

In the following example, a dummy argument strh will assume the length of the associated actual argument, while the other two variables retain a length of 8:

  CHARACTER *8 strg, strh(*), stri

The following examples show ways to specify strings of known length:

  CHARACTER*32 string1

  CHARACTER string2*32

The following examples show ways to specify strings of unknown length:

  CHARACTER string3*(*)

  CHARACTER*(*) string4

The following example declares an array NAMES containing 100 32-character elements, an array SOCSEC containing 100 9-character elements, and a variable NAMETY that is 10 characters long and has an initial value of 'ABCDEFGHIJ'.

  CHARACTER*32 NAMES(100),SOCSEC(100)*9,NAMETY*10 /'ABCDEFGHIJ'/

The following example includes a CHARACTER statement declaring two 8-character variables, LAST and FIRST.

  INTEGER, PARAMETER :: LENGTH=4

  CHARACTER*(4+LENGTH) LAST, FIRST

The following example shows a CHARACTER statement declaring an array LETTER containing 26 one-character elements. It also declares a dummy argument BUBBLE that has a passed length defined by the calling program.

  CHARACTER LETTER(26), BUBBLE*(*)

In the following example, NAME2 is an automatic object:

  SUBROUTINE AUTO_NAME(NAME1)

    CHARACTER(LEN = *) NAME1

    CHARACTER(LEN = LEN(NAME1)) NAME2

The following examples show deferred-length CHARACTER variables:

CHARACTER(:), ALLOCATABLE :: namea

ALLOCATE (CHARACTER(10)::name6)

namea = 'ABCDEF'  ! Allocates or reallocates namea to length 6

Declarations for Character Types

Description

Examples

See Also