Program student_records
!------------------------------------------------------------------------------
!Program: Student Record GPA Calculator with File I/O
!Author: Chris Harper
!Date: 2/17/2008
!------------------------------------------------------------------------------

IMPLICIT NONE

!declarations
integer :: ERR, EOF, stuID, hours(4)
real :: grade(4), gpa, points(4)
character (20) :: name

!open files
open(unit = 10, file = "students.dat", status = "old", iostat = ERR)
open(unit = 11, file = "students_gpa.dat", status = "unknown")

!if no error
if (ERR == 0) then
	!for all lines in the input file
	do
		!read the formatted line
		!grades and hours go into an array
		read (10, "(I9, 1X, A20, 4(1X, I1, 1X, F3.1))", iostat = EOF), & 
		  stuID, name, hours(1), grade(1), hours(2), grade(2), hours(3), grade(3), &
		  hours(4), grade(4)
		
		if (EOF < 0) then
			!if EOF, exit loop
			exit
		else if (EOF > 0) then
			!if error, print a message and exit
			print *, "File read error occured. Error Number: ", EOF
			exit
		endif
		
		!calculate gpa using array functions
		points = hours * grade
		gpa = sum(points) / sum(hours)
		
		!output formatted line
		write(11, "(I9, '|', A20, 4('|', I1, '|', F3.1), '|', F4.2)"), & 
		  stuID, name, hours(1), grade(1), hours(2), grade(2), hours(3), grade(3), &
		  hours(4), grade(4), gpa
	enddo
else
	print *, "File open error occured. Error Number: ", ERR
endif

close(10)
close(11)
end