ERROR 94, Unit has neither been opened or preconnected

Hi,

I am trying to create a executable of the following program, but wen I try to run it, appears the error 94 - Unit has neither been opened or preconnected, at the call READ(,) H1 and I don't andurstand why? Can anyone tell me why this happens?

Thanks for the help!

* PROGRAM ROUTING

C Declaration of variables

   INTEGER N,I,T1,DT
   INTEGER T(250)
   REAL A,K,H,H1,ST
   REAL Q(250),QT(250),HD(250)
   CHARACTER*12 NAMEIN,NAMOUT
   CHARACTER*1 NO,AAA

C Input of data

   WRITE (*,'(A)') ' ***** Flood routing calculation *****'
   WRITE (*,*)
   WRITE (*,'(A)') ' Give the name of input data file:    '
   READ (*,'(A12)') NAMEIN
   OPEN (1,FILE=NAMEIN,STATUS='OLD',ACCESS='SEQUENTIAL')

    READ (1,*) N

C N is the total number of input discharge observations (N ⇐ 250) READ (1,) T1 C T1 is zero time READ (1,) DT C DT is the time increment

    WRITE (*,*)
    WRITE (*,'(A)') ' Input hydrograph:    '
    DO 60 I=1,N
       T(I)=T1+(I-1)*DT
       READ (1,*) Q(I)

C Read discharge at each time. Time increment is constant. WRITE (,) ' Time= ',T(I), ' Discharge= ',Q(I) 60 CONTINUE

   READ (1,*) A

C A is the surface area of the reservoir READ (1,) K C K is the const. in O=KH^(3/2), the ouflow rate in spillway READ (1,*) H C H is the inicial head over the crest of spillway

   CLOSE (1)

   OPEN (2,FILE='Result.dat',STATUS='NEW')

C Help in manual plot of graph O*dt/2+S as a function of H

   WRITE (*,*)
   WRITE (*,'(A)') ' Manual plot graph O*dt/2+S function of H'
   WRITE (*,*)
   WRITE (*,*) ' Initial head over the spillway is = ', H
   WRITE (*,*)

69 WRITE (,'(A)') ' Enter head over crest, H1 ' WRITE (,'(A)') ' (enter NEGATIVE number when complete) :' READ (,) H1

   IF (H1.LT.0.0) THEN
       GOTO 100
    ENDIF

    ST=A*H1+DT*K*H1**(3./2.)/2
    WRITE (*,'(A)') ' Please plot the point:    '
    WRITE (*,*) 'H= ',H1, ' O*dt/2+S= ',ST
    GOTO 69

100 WRITE (,'(A)') ' Is the graphic complete? (Y/N): ' READ (,'(A)') NO IF (NO.EQ. 'N') THEN GOTO 69 ENDIF

   DO 37 I = 1,N-1
       WRITE (*,*) ' Time increment No. : ', I
       WRITE (*,*) ' Head at time: ', I, ' is equal to:'
       READ (*,*) H
       D= K*H**(3./2.)
       S=A*H
       DS=(Q(I)+Q(I+1))*DT/2-D*DT/2+S
       WRITE (*,*) ' O*dt/2+S= ', DS
       QT(I)=D
       HD(I)=H

   WRITE (*,*)
   WRITE (*,'(A)') ' From graph det. H at end time increment.'
   WRITE (*,'(A)') ' When ready press RETURN and enter H.'
   READ (*,'(A)') AAA
       IF (I.EQ.N-1) THEN
         WRITE (*,'(A)') ' Head in the last increment is: '
         READ (*,*) H
         D= K*H**(3./2.)
         QT(I)=D
         HD(I)=H
       ENDIF

37 CONTINUE

C Writing final results in the terminal and in output data file

           WRITE (*,'(A)') ' Time    Inflow    Outflow    Head '

           WRITE (2,'(A)') ' Time    Inflow    Outflow    Head '
       DO 600 I=1,N
           WRITE (*,50) T(I), Q(I), QT(I), HD(I)
           WRITE (2,50) T(I), Q(I), QT(I), HD(I)

600 CONTINUE

50 FORMAT (I5,3F8.2) CLOSE (2) WRITE(*,'(A)') ' ******** END of program ROUTING.FOR ******** ' END

The error probably occurs on a different line. Have you tried using the debugger to run the program?

Yes I already use the debuger. And it point the an error in the same line.

Try using different values for your own UNITs rather than 1 and 2.

UNIT values should start at 7 to avoid predefined values.

This problem is better illustrated by the following code.

program anon

   character(len=10) :: input
   
   open(1,file='File.tmp')
   close(1)
   
   read(*,*) input
   
end program anon

This compiles with these warnings:

warning 868 - Opening unit 1 may affect the operation of input from the default unit '' - are you sure you want to do this? warning 868 - Closing unit 1 may affect the operation of input from the default unit '' - are you sure you want to do this?

And when the code is run, the following error message is generated:

Error 94: Unit has neither been opened or preconnected.

Unit 1 is pre-connected to the keyboard. As far as the Standard is concerned, one is allowed to open a pre-connected unit number and use it. However, when the file associated with the unit is closed, the compiler is not required to re-establish the 'old' pre-connection.

Therefore, best advice is to find out what the pre-connected units are and don't use them. I always choose unit numbers between 10 and 60.

I wouldn't use 7 either as its sometimes pre-connected to the terminal for 'error messages', at least in unix and linux.

If you want to be absolutely portable, you can check if a unit number is valid and not pre-connected using INQUIRE.