Using subroutine inside module in Fortran 90 - module

Question

I have a question concerning using a subroutine inside a module in Fortran 90. Here is my code
Module Multiplication
Subroutine Two_times(input,output)
Real :: input,output
output = input * 2.0
End Subroutine Two_times
End Module
Program test_get_command_argument
Use Multiplication: Two_times
Real :: i,j
i = 0.5
Write (*,*) i
Call Two_times(i,j)
Write (*,*) j
End Program
I used ifort to compile the above code. I received the following message.
files_rev.f90(2): error #6218: This statement is positioned incorrectly and/or has syntax errors.
Subroutine Two_times(input,output)
--^
files_rev.f90(4): error #6274: This statement must not appear in the specification part of a module.
output = input * 2.0
----^
files_rev.f90(5): error #6786: This is an invalid statement; an END [MODULE] statement is required.
End Subroutine Two_times
--^
files_rev.f90(5): error #6785: This name does not match the unit name. [TWO_TIMES]
End Subroutine Two_times
-----------------^
files_rev.f90(6): error #6790: This is an invalid statement; an END [PROGRAM] statement is required.
End Module
^
files_rev.f90(9): error #5082: Syntax error, found IDENTIFIER 'MULTIPLICATION' when expecting one of: ( : % [ . = =>
Use Multiplication: Two_times
------^
files_rev.f90(8): warning #5427: Program may contain only one main entry routine
Program test_get_command_argument
--------^
compilation aborted for files_rev.f90 (code 1)
Why I got #6218 and #6274 error messages and how to fix them?

Answer 1

You are missing a contains keyword before the subroutine declaration and an only keyword after use. Or you can drop : Two_times to use everything in your module. So a working code would look like below:
Module Multiplication
Contains
Subroutine Two_times(input,output)
Real :: input,output
output = input * 2.0
End Subroutine Two_times
End Module
Program test_get_command_argument
Use Multiplication, Only: Two_times
Real :: i,j
i = 0.5
Write (*,*) i
Call Two_times(i,j)
Write (*,*) j
End Program
Take a look at this answer, Can't compile with module and main program in same file, as well, for the missing contains.