Microsoft KB Archive/123690

= Using INTDOSQQ for Keyboard Input in FORTRAN 5.1 =

PSS ID Number: 123690

Article Last Modified on 11/3/1999

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The information in this article applies to:


 * Microsoft FORTRAN Compiler for MS-DOS 5.1

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This article was previously published under Q123690



SUMMARY
This article provides information and sample code on how to check for the presence of keyboard input and get the keybord input with (or without) echoing the keys to the screen.



MORE INFORMATION
Page 273 of the Microsoft FORTRAN version 5.1 "Reference" manual explains how to use the INTDOSQQ and INTDOSXQQ subroutines to invoke MS-DOS Interrupt 21h system calls. Two of these Int 21h functions, functions 7 and 8, get input from the keyboard without echoing that input to the display. The difference between these two functions is that function 7 ignores CTRL+C and CTRL+BREAK characters while function 8 handles these characters by breaking out of the program. The function B (hex) checks to see if a key was pressed. It will return true if a key is waiting to be read, and false if it is called after all of the keys have been read.

What the Sample Code Does
The sample code function GETCH uses MS-DOS Int 21h, function 8 to get a character from Standard Input without echoing it to the screen.

The sample code subroutine PUTCHAR uses Int 21h function 2 to write a single character to the screen.

The sample code PASSWORD uses GETCH to allow input of a password without echoing the keystrokes to the display. PUTCHAR is used to display an asterisk for each keystroke entered.

The sample code function KBHIT uses Int 21h function B(hex) to check if a key was pressed. It returns 0 if no key is available and returns non-zero if a key was pressed. Use GETCH to get the key(s).

NOTE: If several of the routines are put into the same file, then the statement:

include 'flib.fi'

should only be included once at the beginning of that file. (FLIB.FD needs to be included in each subroutine, but FLIB.FI does not.)

Sample Code: GETCH
C Compile options needed: none include 'flib.fi' integer*2 function getch include 'flib.fd' record /regs$info/ in,out in.bregs.ah=#08            ! Function 8 - STDIN Input (no echo) call intdosqq(in,out)      ! Int 21h getch=out.bregs.al         ! Input data returned in AL     return end

Sample Code: PUTCHAR
C Compile options needed: none

include 'flib.fi' subroutine putchar( ch ) include 'flib.fd' record /regs$info/ in,out character*1 ch     in.bregs.ah=#02             ! Function 2 - Display Output in.bregs.dl=ch             ! Character to display goes in DL     call intdosqq(in,out)       ! Int 21h return end

Sample Code: PASSWORD
C Compile options needed: none include 'flib.fi' program password character*80 pass logical get_pass/.true./ integer*2 i,j,getch write(*,'(1x,a,\)') 'ENTER PASSWORD > ' i=1 do while (get_pass) j=getch                 ! Get a character of the password if (j.le.32) then if (j.eq.8.and.i.gt.1) then ! BACKSPACE key pressed i=i-1 call putchar( char(j) )! Move cursor back one character call putchar( ' ' )   ! Write a blank over the asterisk call putchar ( char(j) )! Move cursor back to blanks pass(i:i+1) = ' ' endif if (j.eq.13) get_pass=.false.! ENTER key pressed -- exit else call putchar( '*' )       ! Echo asterisk to display pass(i:i)=char(j)         ! Add input character to string i=i+1 if (i.gt.80) get_pass=.false. ! Don't write past string end endif enddo write(*,*) write(*,*) 'password entered > ',pass end

Sample Code: KBHIT
C Compile options needed: none include 'flib.fi' integer*2 function kbhit include 'flib.fd' record /regs$info/ in,out in.bregs.ah=#0B            ! Function B - Get STDIN Status call intdosqq(in,out)      ! Int 21h kbhit=out.bregs.al         ! Input data returned in AL     return end

