You're asking two completely different things, so it's not clear which question you want answered or what you're specifically trying to do.
The first was the situation when you have a GPIB card and you want to "simulate GPIB". What exactly do you want to simulate? An instrument? Are you using IVI drivers? If so, you can set one of the configuration parameters when instantiating the IVI driver to simulate that instrument. If you don't have IVI then you will need to create your own simple wrappers for the VISA Write and VISA Read that basically replace the communication you'd get with the instrument. You will probably need to set up some table someplace where you specify the responses to certain commands. I did something similar a while ago. And, no, I don't have the code.
The second was the situation when you don't have a GPIB card and you want to "simulate GPIB card". Again, what exactly are you trying to simulate? If it's an instrument, then the above will work regardless of whether you have a GPIB card or not.
First of all I don't have a GPIB Card. Without using physical GPIB card, can I try some sample programes that involve GPIB communication. IN other words what are the software tools/ components using which I can do GPIB communicatin using LabVIEW.
I dont have idea about IVI drivers etc. If there are any ways to simulate GPIB card, then please let me know!! Are there any tools or simulators already available? Where can these be downloaded/ purchased, where is more informatin on this?
You can get a brief overview on IVI here. They are the only type of driver that has a simulation mode. Even if did have a GPIB board, you would still have errors generated unless you had an actual instrument connected. I know of no 'virtual' controller or 'virtual' instrument package that can be downloaded or purchased. If you want to do some simulation, you could write your own version of VISA Write and VISA Read and provide the same inputs and outputs as they do. It wouldn't do any actual bus communication. You could also simulate some sort of response as well. VISA is the recomended method of GPIB communication instead of the low level GPIB functions. Since the VISA api works with GPIB, serial, USB, Ethernet, VXI, PXI, I would recomend that you use a serial connection. Just loop back the serial port and whatever data you write, you will read back. One of the compelling reasons for VISA is that you only have to learn a single API for communicating over different physical interfaces. A driver written and debugged for an instrument with one physical interface will work for the same instrument with a different interface simply by changing the VISA Resource Name.