DOCUMENT:Q123690  03-NOV-1999  [fortran]
TITLE   :Using INTDOSQQ for Keyboard Input in FORTRAN 5.1
PRODUCT :Microsoft Fortran Compiler
PROD/VER::5.1
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft FORTRAN Compiler for MS-DOS, version 5.1 
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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

REFERENCES
==========

For detailed information about the various Int 21h functions, consult any MS-DOS
programmer's reference manual.

Additional query words: kbinf 5.10 getc getchar console putc

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Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRAN510DOS
Version           : :5.1

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