Why does using command PRINT in Fortran overwrite the input file?

Question

I\'m writing my code and using input and output feature in Fortran. The code looks like this (only for simplification):

PROGRAM TEST

  REAL, DIMENSION(         


        

Answer 1

I've found the answers. Actually the code I've posted above will run well on Gfortran 5.3, since I used OPEN(UNIT=1,...) and OPEN(UNIT=2,...) which is there will be no problem since I am using 1 and 2. I just wrote this simple case to represent my real code without checking it first. But actually in my real code, I used two statements that OPEN(UNIT=5,...) and OPEN(UNIT=6,...) existed, which are not allowed in Fortran, since:

1. UNIT=5 declares Standard In which is used to read in data from the keyboard.
2. UNIT=6 declares Standard Out which is used to print general output to the screen.
3. UNIT=0 declares Standard Error which is used to print error messages to the screen.

I didn't realize before since I'm working on quite old code, so O need to rewrite it into a newer version one. So, in order to avoid the problems, just don't use UNIT=5, UNIT=6 and UNIT=0.