Question

I encountered this problem while solving a practice test

Consider the following code written in a pass-by-reference language like
FORTRAN and these statements about the code

  subroutine swap(ix,iy)
    it = ix
    ix = iy    ! line L1
    iy = it    ! line L2
  end

  program main
    ia = 3
    ib = 8
    call swap (ia, ib+5)
    print *, ia, ib
  end program

Statements:

1. The compiler will generate code to allocate a temporary nameless cell,
   initialize it to 13, and pass the address of the cell swap
2. On execution the code will generate a runtime error on line L1
3. On execution the code will generate a runtime error on line L2
4. The program will print 13 and 8
5. The program will print 13 and -2

Which of the above the above statement(s) is/are correct.

I think S1 and S4. Could anyone please confirm? TIA

Answer 1

Yes, S1 and S4 are correct.

Also,

S0a: The file is not compilable as is because the L1: and L2: are syntax errors. 🙂

S0b: Strictly speaking, speaking of FORTRAN as a pass-by-reference language is incorrect:

• The name of the language is Fortran

• Pass by reference is an implementation detail that is not specified in the standard. Copy-in, copy-out is another possible implementation. Also, some newer Fortran language features (F90+) in practice imply an implementation which is neither pass-by-reference nor copy-in-copy-out. See e.g. pointer as a dummy argument and http://software.intel.com/en-us/blogs/2009/03/31/doctor-fortran-in-ive-come-here-for-an-argument/