How Declare Global variables [duplicate] - fortran

Question

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How to avoid declaring and setting the value of a variable in each subroutine?
(1 answer)
Closed 5 years ago.
I have a program that calls functions within the same program but I want to declare and initialize the variables on the top and access them at the end of the program.
!Declaration
INTEGER TOPCHORD,BOTCHORD, SUPPS, PURLINS;
!Initialization
! Define Layers for connecting lines
TOPCHORD = 32
BOTCHORD = 32
SUPPS = 36
PURLINS = 30
INTEGER FUNCTION IFLANGE1(IEND1,IEND2,ISUP)
IFLANGE1=TOPCHORD
SELECT CASE(IEND1)
CASE(2,4,6,8,9,10)
IFLANGE1=BOTCHORD
IF(ISUP.EQ.1)IFLANGE1=SUPPS
END SELECT
SELECT CASE(IEND2)
CASE(2,4,6,8,9,10)
IFLANGE1=BOTCHORD
IF(ISUP.EQ.1)IFLANGE1=SUPPS
END SELECT
RETURN
END
I get error that variable 'SUPPS' referenced but not set

Answer 1

You might want to have a look at the documentation - you're missing a couple of important statements. (Also try to always include implicit none -- this is very helpful for catching certain issues).
A slightly modified code that should compile is
!Declaration
INTEGER TOPCHORD,BOTCHORD, SUPPS, PURLINS;
!Initialization
! Define Layers for connecting lines
TOPCHORD = 32
BOTCHORD = 32
SUPPS = 36
PURLINS = 30
contains !Indicate that the program unit contains other procedures
INTEGER FUNCTION IFLANGE1(IEND1,IEND2,ISUP)
IFLANGE1=TOPCHORD
SELECT CASE(IEND1)
CASE(2,4,6,8,9,10)
IFLANGE1=BOTCHORD
IF(ISUP.EQ.1)IFLANGE1=SUPPS
END SELECT
SELECT CASE(IEND2)
CASE(2,4,6,8,9,10)
IFLANGE1=BOTCHORD
IF(ISUP.EQ.1)IFLANGE1=SUPPS
END SELECT
RETURN
END FUNCTION !End the function definition
END !This is a required end statement to say we've reached the end of the program
This isn't the nicest style etc. but has the minimum number of changes to compile.
For any slightly more complex program I would strongly recommend using modules for storing variables (and also procedures) that you want to access from different parts of the code.