PROGRAM ACCESS FOR DIFFERENT PROGRAMMING LANGUAGES UNDER MS-DOS.
_________________________________________________________________


- Data write to LPT port
****************************

Turbo Pascal 7.0
------------------
Uses Dos;

Var
   addr:word;
   data:byte;
   e:integer;

Begin
   addr:=MemW[$0040:$0008];
   Val(ParamStr(1),data,e);
   Port[addr]:=data;
End.

For determination of port address there is used representation for BIOS, where addr:=MemW[$0040:$0008] presents LPT1 abd address addr:=MemW[$0040:$000A] presents LPT2 port.


Assembler:
----------------------
MOV DX,0378H
MOV AL,n
OUT DX,AL 

where n means transmitted data (byte) to LPT1 port (0x378). 


BASIC:
----------------------
OUT &H378, N

where n means transmitted data (byte) to LPT1 port (0x378). 


Programovací jazyk C:
----------------------
outp(0x378,n);
nebo 
outportb(0x378,n);

where n means transmitted data (byte) to LPT1 port (0x378). 

For C language is necessery to write a declaration of variables and libraries.
Following example is for Borland C++ 3.1 compiler.


#include <stdio.h>
#include <dos.h>
#include <conio.h>

/********************************************/
/*This program set the parallel port outputs*/
/********************************************/

void main (void)
{
clrscr();             /* clear screen */
outportb(0x378,0xff); /* output the data to parallel port */
getch();              /* wait for keypress before exiting */
}


FOR CONTROL OF LPT PORT UNDER OS LINUX AND PROGRAMMING LANGUAGE C 
////////////////////////////////////////////////////

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <asm/io.h>

#define base 0x378           /* printer port base address */
#define value 255            /* numeric value to send to printer port */

main(int argc, char **argv)
{
   if (ioperm(base,1,1))
    fprintf(stderr, "Couldn't get the port at %x\n", base), exit(1);

   outb(value, base);
}

If this source code is saved for example into file lpt_test.c, it can be compile by command: 

gcc -O lpt_test.c -o lpt_test

---------------------------------------------------------------------
- Data read from LPT port
****************************
Assembler:
-----------------------------------
MOV DX,0379H
IN AL,DX

Resulting value of the register is in accumulator AL.


BASIC:
------------------------------------
N = INP(&H379);

where N je the resulting read value from register.


Programovac jazyk C:
-------------------------------------
in = inportb(0x379);
nebo  
in = inp(0x379);

where N je the resulting read value. Variable declaration can be achieved in according to previous presented program for value listing for Borland C++ 3.1 compiler.