Is there a fundamental difference in the way which the OS of DCS & PLC's process the user programs. PLC's - What i think i know - Scan the inputs, and write into Process Input Image - Process, execute user programs - Write down the outputs into Process Output Image -----------Original Question---------------- Hi! All I got a ludicrous question here folks. Though it has nothing to do with I/A, but this forum has some of the best brains around to put the answer to a query like this one, in right words. - Today we all know that any PLC can do PID control, any DCS can do ladder, - But still we all know that there are applications where we won't use DCS, and there are applications where we won't use PLC. Why ??? I will summarize... Thanks & Regards Ajay Tathgir Reliance Industries Limited Mumbai - India _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave