Mainframe systems are still the source of truth in many companies and integration technologies are used to represent and exchange that data. As Jeane mentioned there won't be any new development work except for minor enhancements and maintenance of those systems.
Originally posted by Abdul Kader: what is the difference in creating a web application or a minframe application ?
Abdul Kader, there is nothing in common (even though you might use a mainframe computer as a web server). Mainframe computers are computers used mainly by large organizations for critical applications, typically bulk data processing such as census, industry and consumer statistics, ERP, and financial transaction processing. Please check this wikipedia article
IBM's the one to watch on that one. Mostly because they're about the only mainframe vendor left, but also because they've been pretty good at adapting to the times.
One of their latest selling points is using mainframes to host multiple Linux VMs. It's cost-effective because one mainframe typically can do the work of several racks of servers and pulls less overall power.
The major difference between mainframes and server machines these days is primarily 3 things:
1. Mainframes are not allowed to go down. Period. Mainframes are designed at both the OS and hardware level not to crash. It comes from the days when one computer had to serve the whole company and you could idle literally hundreds of people while the system was down.
2. Mainframe programs tend to be more efficient. Many of the legacy apps were designed back when a Megabyte of RAM was a big thing. Some of the oldest system utilities were written to run in systems with less than 64 Kilobytes. Hardware was expensive and there was less incentive to do it "quick and dirty".
3. At the hardware level, mainframes tend to be slower than server systems, since they can't upgrade CPUs as easily when a new one comes along. On the other hand, they're built for reliability, and - most importantly - they're optimized at the hardware level for I/O. Mainframes can shove data around better than just about anything.
An IDE is no substitute for an Intelligent Developer.