Hello pratik;

OPC is a way to exchange data between partners (servers that provide information and clients that request it), originally based on Microsoft COM and DCOM standards. It is now an easy-to-configure interface that allows information exchnge withoutm having to develop specific communication drivers.

Have a look here for some basic information, on OPC and OPC on Siemens hardware:

- From the OPC Foundation: What is OPC?

http://opcf.org/Default.aspx/01_about/01_whatis.asp?MID=AboutOPC

- From Siemens: manuals on OPC configuration and programming

SIMATIC NET PC software Industrial Communication with PG/PC Volume 1 - Basics System Manual

SIMATIC NET PC software Industrial Communication with PG/PC Volume 2 - Interfaces Programming Manual

SIMATIC NET PC software Commissioning PC Stations - Manual and Quick Start Configuration Manual

Hope this helps,

Daniel Chartier