i was just looking at job interview questions, and one was "What are the advantages and disadvantages of a client-server application versus a mainframe-based application?" i haven't worked with mainframes. can someone enlighten me?

With a mainframe you use "dumb terminals" (ie: just a keyboard and monitor wiht no processing power) to access the programs and data stored on it. Any and all processing is done on the mainframe itself. The advantage of a client/server setup is that the processing is done locally on the client PC thus freeing up the server for other things. So with a client/server application...the main database for it is stored on the server (a central location), but when you run the program, it runs locally on the client PC you're using. Advantages of a mainframe over a client/server network...NONE!

Some would say the advantage of the mainframe over a pc net with client/servers is the cost of the dumb termnial, only $350 each. But the same people never mention that the mainframe costs many 10's of thousands, as opposed to a few thousand for a pc server.

These days you can build clients for around $350 so that isn't an advantage anymore.

This is a very strange question! A Mainframe is involved in a lot of client-server application. Even an old mainframe application (accessed with dumb terminal) may be easily converted to a client-server GUI application with some cgi. Advantages of mainframe over client-server? It work! No client software problem, no MS-windows problem, no virus/worm/trojan, no memory or space problem (except for the server itself). This is why several financial organization still use mainframe based application for their legacy applications.