Abbas,
The full IEEE Specification can be ordered from IEEE's web site: www.ieee.org. Our bus extenders adhear to this spec. More information can be found in the user manuals for these products on our web site.
National Instruments' web site also has many resources on GPIB. If you go to www.ni.com and click on Support, you will be taken to the main support page. Under Option 2, select GPIB to go to the main GPIB support page. On this page are many tutorials, example code, and installation information. Hope this information helps.
Sarah Fenney
Applications Engineer
National Instruments