HOW TO PROGRAM THE PARALLEL PORT ON A COMPUTER USING C/C++

New versions of windows operating system does not support direct access to I/O ports.

In order to communicate with the parallel port of your computer in windows operating system you will need a driver called inpout32.dll which you can dowload from here http://logix4u.net/parallel-port/inpout32_source_and_bins.zip

Extract the zip file , open the binaries directory , copy the inpout32.dll and add it to you projects directory.
you can also save it at "%systemroot%\system32\drivers"

The address of the parallel data port is 
0x378-0x37F for LPT1
0X278-0X27F for LPT2

Parallel port has 8 data input

fig.1

DATA PORT PIN NO.	SIGNAL NAME	BYTE TO ACTIVATE PIN
2	D0	0x01
3	D1	0x02
4	D2	0x04
5	D3	0x08
6	D4	0x10
7	D5	0x20
8	D6	0x40
9	D7	0x80
18-25	Ground(GND)

All the data port are latching which means it keeps it state once it is activated.

To send one byte to the parallel port  
 send 0xFF to 0x378

1 bit will be on each data port which means all the data port will have 5V across them

To send 1 bit to Data port 

If you send 0x01 to data port 0x378 will send binary 00000001(5V) to pin 1
and so on as shown on the table.

Now to start create a new cpp file  and note the inpout32.dll should be in the same folder or you can place in this directory %systemroot%\system32\drivers.

This is how your code should start

To send 1 bit to data port pin 1( D0 ) out(0x378, 0x01) and the rest can be found on the table 

Here is a simple example to demonstrate how to switch the data port of the paraport on and off .

setup a circuit as shown below

fig.2

And the source code is here:

Output display below

fig. 3

With this you can control many appliance and device with the help of a relay.
 The next blog is about How to use the Parallel Port to control a 240 V light bulb