Intel fortran-80 manual EQUIVALENCE Statement, Memory Definition, DATA I,J,K/10,20,301

FORTRAN-80 Defining Variables, Arrays, And Memory

Items in DATA lists must agree in number, type, and length.

'Nlist' and 'elist' must have the same number of items, as the lists correspond one- to-one. If 'nlist' contains an array name without a subscript, 'elist' must have one constant for each element of that array (but see section F.2.9.2). Any subscript that is specified must be an integer constant.

The type of a name specified in 'nlist' must agree with the type of the corresponding constant in 'elist,' except that an item of any type can be initialized to a Hollerith constant.

Given a length 'g' of a variable or array element in 'nlist,' then the length In' of its corresponding initial Hollerith constant in 'elist' must be less than or equal to 'g.' If 'n' is less than' g,' the constant is padded on the right with blanks until the lengths are equal. Note that initialization of a character in a variable or array element in- itializes that entire item.

A variable or array element cannot be initialized more than once in a program. If two symbols are associated, only one may be initialized.

Examples:

DATA I,J,K/10,20,301

CHARACTER*10 NAMES(3)

DATA NAMES/'GEHRIG','OTT','RUTH'I

INTEGER*1 ZEROS (10)

DATA ZEROS 110*0/1,J,K 110,20,301 &NAMES(2) I'OTT'I

C AMPERSAND USED TO CONTINUE STATEMENT

LOGICAL TABLE(3)

DATA TABLE I.TRUE., .TRUE., .FALSE.!

3.4 Memory Definition

The DATA and assignment statements assign values to specific items. FORTRAN also ineludes three statements for establishing memory areas and initializing these areas. These are the EQUIVALENCE, COMMON, and BLOCK DATA statements.

EQUIVALENCE is used to associate two or more items in memory, such as associating a variable name with an array element. Its scope is the program unit in which it appears. The COMMON statement can be used to associate items in dif- ferent program units, allowing common use of data and memory through an entire program (for example, a common data base or table). BLOCK DATA defines a BLOCK DATA subprogram, which can assign initial values to items in common memory.

3.4.1 EQUIVALENCE Statement

The EQUIVALENCE statement allows items in a program unit to share memory. All entities listed in the EQUIVALENCE statement share the same start address in memory (even if they are of unequal lengths).

The format of the EQUIVALENCE statement is:

EQUIVALENCE (nlist) [,(nlist)] ...

3-11