Open Watcom FORTRAN 77 Language Reference

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Language Reference Example: * From the quadratic equation * * 2 * ax + bx + c = 0 * * we derive the following two equations: * ____________ * + / 2 * -b - \/ b - 4ac * x = --------------------- * 2a * * and express these equations in FORTRAN as: X1 = ( -B + SQRT( B**2 - 4 * A * C ) ) $ / ( 2 * A ) X2 = ( -B - SQRT( B**2 - 4 * A * C ) ) $ / ( 2 * A ) 1.4 Order of FORTRAN Statements and Lines The first statement of a program unit may be a PROGRAM, FUNCTION, SUBROUTINE, or BLOCK DATA statement. The PROGRAM statement identifies the start of a main program and there may only be one of these in an executable FORTRAN program. Execution of a FORTRAN program begins with the first executable statement in the main program. The other statements identify the start of a subprogram. If the first statement of a program unit is not one of the above then the program unit is considered to be a main program. Although you may not be familiar with all of the terms used here, it is important that you understand that FORTRAN 77 has specific rules regarding the ordering of FORTRAN statements. You may wish to refer to this section at later times. In general, the following rules apply to the order of statements and comment lines within a program unit: 1. Comment lines and INCLUDE statements may appear anywhere. 2. FORMAT statements may appear anywhere in a subprogram. 3. All specification statements must precede all DATA statements, statement function statements, and executable statements. 4. All statement function statements must precede all executable statements. 5. DATA statements may appear anywhere after the specification statements. 6. ENTRY statements may appear anywhere except between a block IF statement and its corresponding END IF statement, or between a DO statement and its corresponding terminal statement. Open Watcom FORTRAN 77 extends these rules to apply to all program structure blocks resulting from the use of statements introduced to the language by Open Watcom FORTRAN 77 (e.g., WHILE, LOOP, SELECT). 7. IMPLICIT statements must precede all other specification statements, except PARAMETER statements. A specification statement that defines the type of a symbolic constant must appear 6 Order of FORTRAN Statements and Lines
FORTRAN Source Program Format before the PARAMETER statement that defines the name and value of a symbolic constant. A PARAMETER statement that defines the name and value of a symbolic constant must precede all other statements containing a reference to that symbolic constant. The following chart illustrates the required order of FORTRAN statements. Vertical lines delineate varieties of statements that may be interspersed, while horizontal lines mark varieties of statements that may not be interspersed. PROGRAM, FUNCTION, SUBROUTINE, or BLOCK DATA Statement PARAMETER IMPLICIT Statements Comment ENTRY Statements Other Lines Specification and Statements FORMAT Statement INCLUDE Function Statement Statements DATA Statements Statements Executable Statements END Statement Required Order of Comment Lines and Statements For example, DATA statements may be interspersed with statement function statements and executable statements but statement function statements must precede executable statements. Order of FORTRAN Statements and Lines 7
Page 1 and 2: Open Watcom FORTRAN 77 Language Ref
Page 3: Preface Open Watcom FORTRAN 77 is a
Page 6 and 7: Table of Contents 2.25 ELSE IF Stat
Page 8 and 9: Table of Contents 3.4.10 Hexadecima
Page 10 and 11: Table of Contents 11.7 Editing ....
Page 12 and 13: Table of Contents 12.6.1 ENTRY Stat
Page 14 and 15: Language Reference 2
Page 16 and 17: Language Reference 1.3 Source Progr
Page 20 and 21: Language Reference 8 Order of FORTR
Page 22 and 23: Language Reference Statement 1 2 3
Page 24 and 25: Language Reference 2.3 ADMIT Statem
Page 26 and 27: Language Reference If there is a LO
Page 28 and 29: Language Reference 2.5 Statement La
Page 30 and 31: Language Reference 2.6 AT END State
Page 32 and 33: Language Reference The FORTRAN 77 s
Page 34 and 35: Language Reference 6. A named block
Page 36 and 37: Language Reference It is important
Page 38 and 39: Language Reference 2.11 CHARACTER S
Page 40 and 41: Language Reference If a symbolic na
Page 42 and 43: Language Reference Example: LOOP RE
Page 44 and 45: Language Reference Example: REAL A,
Page 46 and 47: Language Reference a (d) len is an
Page 48 and 49: Language Reference 2.15 CONTINUE St
Page 50 and 51: Language Reference 2.17 DATA Statem
Page 52 and 53: Language Reference 2. As an extensi
Page 54 and 55: Language Reference 2.18 DEALLOCATE
Page 56 and 57: Language Reference 2.19 DIMENSION S
Page 58 and 59: Language Reference Transfer of cont
Page 60 and 61: Language Reference Example: * Illeg
Page 62 and 63: Language Reference c r is a constan
Page 64 and 65: Language Reference c r is a constan
Page 66 and 67: Language Reference 2.24 ELSE Statem
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Language Reference 2.26 END Stateme
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Language Reference 2.28 END BLOCK S
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Language Reference 2.30 ENDFILE Sta
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Language Reference 2.31 END GUESS S
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Language Reference 2.33 END LOOP St
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Language Reference 2.35 END SELECT
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Language Reference 2.37 END UNION S
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Language Reference 2.39 ENTRY State
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Language Reference The following ex
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Language Reference 2.42 EXIT Statem
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Language Reference 2.44 FORMAT Stat
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Language Reference 2.45.2 Extended
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Language Reference 2.47 Computed GO
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Language Reference * Illegal use of
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Language Reference 2.50 Arithmetic
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Language Reference An example of an
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Language Reference IF( I .EQ. 10 )T
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Language Reference 2.53.3 IMPLICIT
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Language Reference 2.54 INCLUDE Sta
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Language Reference Example: LOGICAL
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Language Reference It is assigned t
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Language Reference 3. This specifie
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Language Reference a (d) len is an
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Language Reference 2.57 INTRINSIC S
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Language Reference 2.59 LOOP Statem
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Language Reference 2.61 NAMELIST St
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Language Reference Example: &PERSON
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Language Reference FILE = fin fin i
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Language Reference Notes: 1. If the
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Language Reference 2.64 PARAMETER S
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Language Reference 2.66 PRINT State
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Language Reference Example: PRINT 1
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Language Reference 2.68 QUIT Statem
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Language Reference 2. An internal f
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Language Reference Example: READ( 8
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Language Reference 2.71 RECORD Stat
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Language Reference 2.73 RETURN Stat
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Language Reference Notes: 1. The un
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Language Reference PROGRAM MAIN . .
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Language Reference Example: SELECT
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Language Reference 2.78 STRUCTURE S
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Language Reference 2.80 UNION State
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Language Reference 2.82 VOLATILE St
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Language Reference 2.84 WHILE State
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Language Reference REC = rn IOSTAT
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Language Reference 150
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Language Reference Example: DO10I=1
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Language Reference 123.764 .4352344
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Language Reference Actually, holler
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Language Reference 158 Symbolic Con
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Language Reference [lo:] hi where:
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Language Reference 4.4 Classifying
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Language Reference 4.5 Classifying
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Language Reference Example: CHARACT
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Language Reference STRUCTURE /PERSO
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Language Reference SUBROUTINE PRINT
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Language Reference 172 Unions
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Language Reference Operator Arithme
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Language Reference 7.1.3 Arithmetic
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Language Reference 7.2 Character Ex
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Language Reference where: relop is
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Language Reference Note that the op
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Language Reference 1. logical term
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Language Reference 186 Constant Exp
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Language Reference 8.3 Logical Assi
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Language Reference 8.6 Extended Ass
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Language Reference 192 Extended Ass
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Language Reference Examples follow
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Language Reference 9.4 DO - END DO
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Language Reference The next example
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Language Reference where: stmt is a
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Language Reference Example: * Illeg
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Language Reference - the string -10
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Language Reference 9.12 GUESS-ADMIT
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Language Reference 9.13 QUIT QUIT [
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Language Reference Example: LOOP RE
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Language Reference READ statement t
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Language Reference 214 Notes on Str
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Language Reference 10.3 Records FOR
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Language Reference accessed directl
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Language Reference Example: WRITE(1
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Language Reference 5. Any character
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Language Reference 224 Printing of
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Language Reference Example: REAL X
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Language Reference 11.6 Nonrepeatab
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Language Reference Example: PRINT
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Language Reference Example: INTEGER
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Language Reference 11.7.10.4 E and
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Language Reference n Example: is 4
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Language Reference and is read into
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Language Reference 3. An input item
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Language Reference 1. Blanks are ne
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Language Reference e is an expressi
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Language Reference Example: * Illeg
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Language Reference 12.3.2 Type Conv
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Language Reference 12.3.7 Type Conv
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Language Reference 12.3.13 Remainde
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Language Reference 12.3.18 Choosing
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Language Reference 12.3.24 Square R
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Language Reference 12.3.28 Sine Def
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Language Reference 12.3.33 Arccosin
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Language Reference 12.3.38 Gamma Fu
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Language Reference 12.3.45 Lexicall
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Language Reference Definition: Name
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Language Reference 12.3.53 Binary P
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Language Reference 12.3.58 Allocate
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Language Reference Example: INTEGER
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Language Reference 2. An array name
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Language Reference 5. A name that a
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Language Reference 12.8.1 Dummy Arg
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Language Reference Example: DIMENSI
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Language Reference 282 Subprogram A
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Appendices 284
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Appendices 10. The DOUBLE COMPLEX s
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Appendices 36. Non-character arrays
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Index AMAX1 253 AMIN0 254 $ AMIN1 2
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Index DATAN 260 dummy procedure 280
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Index AINT 250 ANINT 251 ASIN 259 H
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Index DREAL 249 IAND 264 DSIGN 252
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Index RETURN 32, 46, 56, 121, 132,
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Open Watcom FORTRAN 77 Language Reference

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