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Posted 17 Aug 2004

Port Access

, 17 Aug 2004
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A way to access parallel port in Windows XP


At first I want to thank Mr. Tomas Franzon as I used his help a lot in this project. This code opens and closes 0x378 port ( printer port ) manually. In XP we have no permission to access external port like Printer. Here we copy a sys file to system32 and use it in the code so we can send and receive data through this port.

Using the code

For using the code you have to copy PortAccess.sys ( exists in source ) to system32\drivers. Then you can run the program.

For sending and receiving data we do this :

#include <conio.h>
#include <math.h>

         // for sending data


Return Value:

This function returns data output . There is no error return.


Unsigned short Port Number ( defined 0x378 )

Int Output value

// for receiving data

Return Value:

This function returns the byte, word or int from port. There is no error report


Unsigned short Port Number ( defined 0x378 )

When you check a check box the iBitOut value is Set or Reset.

// to set or reset a bit

When you click output button the Bits are changed to int value to send to port.

// to send value to port


for (i=0;i<=7;i++)







When you click input button the input value is read and iBitIn[i] becomes set or reset.

// to get data from port


for (i=7;i>=0;i--)



        if (iByte>=nIndex)

        {        iByte=iByte-nIndex;



        else iBitIn[i]=0;


For checking a check box we use code below :

// to check a check box

if (iBitIn[0]==1)

Points of Interest

I always work with peripheral devices. In these cases, communicating in parallel mode is more flexible and easier than the other modes like serial communication. So I am forced to go to this field. You can send and receive int, long, Byte, unsigned short, unsigned char etc as easy as possible.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Web Developer
Iran (Islamic Republic of) Iran (Islamic Republic of)
I live in Iran . I started hardware programming when I was young. I designed and built some ISA cards for attaching to ocsiloscope and signal generator. Now I am working for a engineering company and Manager of some project.

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Comments and Discussions

Questiona question from lovers_ali Pin
Sean Ewington6-Jun-07 8:41
adminSean Ewington6-Jun-07 8:41 
AnswerRe: a question from lovers_ali Pin
asef9-Jun-07 19:26
memberasef9-Jun-07 19:26 
Hi Go to this link. It works well:

Have fun
Smile | :)


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