Main program

A main program is a program unit. There must be exactly one main program in an executable program. Execution always begins with the main program.

The main program can determine the overall design and structure of the complete program and often performs various computations by referencing procedures. A program may consist of the main program alone, in which case all the program logic is contained within it.

A main program has the form:

[PROGRAM program-name]
   [specification-part]
   [execution-part]
   [internal-procedure-part]
END [PROGRAM [program-name]]

program-name

i s the name of the program. program-name can appear on the END PROGRAM statement only if it also appears on the PROGRAM statement; the name must be the same in both places.

specification-part

is zero or more of the statements listed in Table 7-1 “Specification statements” as well as any of the following:

Type declaration statement
Derived-type definition
Interface block
Statement function
Cray-style pointer statement (HP extension)
Structure definition (HP extension)
Record declaration (HP extension)

execution-part

is zero or more of the statements or constructs listed in Table 7-2 “Executable statements” as well as any of the following:

Assignment statement
Pointer assignment statement

internal-procedure-part

takes the form:

CONTAINS
    [internal-procedure]...

where internal-procedure is one or more internal procedures; see “Internal procedures”.

Table 7-1 Specification statements

`ALLOCATABLE`	`FORMAT`	`POINTER`
`COMMON`	`IMPLICIT`	`SAVE`
`DATA`	`INTRINSIC`	`STATIC`
`DIMENSION`	`NAMELIST`	`USE`
`EQUIVALENCE`	`OPTIONAL`	`VIRTUAL`
`EXTERNAL`	`PARAMETER`	`VOLATILE`

Table 7-2 Executable statements

`ACCEPT`	`ELSE`	`ON`
`ALLOCATE`	`ELSE IF`	`OPEN`
`ASSIGN`	`ELSEWHERE`	`PAUSE`
`BACKSPACE`	`ENCODE`	`PRINT`
`CALL`	`END`	`READ`
`CASE` construct	`ENDFILE`	`REWIND`
`CLOSE`	`EXIT`	`STOP`
`CONTINUE`	`FORMAT`	`TYPE` (I/O)
`CYCLE`	`GO TO`	`WHERE`
`DEALLOCATE`	`IF`	`WHERE` construct
`DECODE`	`IF` construct	`WRITE`
`DO`	`INQUIRE`
`DO` construct	`NULLIFY`

The only required component of a main program unit is the END statement. The following is therefore a valid, compilable program:

END

Main program

Technical documentation

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