Program status word or PSW
Program Status pg 367 operating systems
IBM is still the leader in Mainframes..
IBM Mainframes
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The first mainframes were large enough to fill an entire room. The mainframes today created by IBM are about the size of your household refrigerator.
IBM's pg. 366 operating systems
There are mainframe computers, mini computers and micro computers. Mainframes are large scale computers, (search IBM System/360) mini computer are smaller, a lot smaller than mainframes (search IBM AS/300) and minis are what's on your desktop like a DELL, HP, Sony, etc.
DOSUnix and all its varientsC/PMMVS and OS series for IBM mainframes
4
Yes, from first versions of the IBM 360 architecture there are different interrupt types that put the system into Supervisor mode and invoke the operating system to analyze the interrupt type
The first spelling verification program was written for IBM mainframes in the late 1970's. The original was designed by a team of linguists from Georgetown University.
OS/390, OS/400 are still alive and they rock!
Most computers use ASCII (or some similar) encoding, in which 'A' is represented as 65, or 01000001 binary. Older IBM mainframes use an entirely different encoding.