On Thu, 17 Dec 2009 18:06:04 +0100, Lindy Mayfield wrote: >I've often heard that programs that ran on the IBM 360 will still >run on a z/10. Is this true? Some? Most? All?
True, with very few exceptions. John already mentioned privileged instructions. I/O instructions, for example, were completely replaced with XA in the early 1980's. Normal problem-state programs do not use these instructions though. They rely on the operating system to do their I/O for them. The operating system has carefully maintained this application program compatibility as well. Of course, it was always possible to design a program so that it was dependent on particular machine characteristics. If you had a cpu loop that was designed to cause your processing to wait for a period of time, it would end much sooner today. Or if you had a program that depended on the track and cylinder size of a 2314, you'd be out of luck today. Another case is the ASCII bit. Bit 12 of the 360 PSW was the ASCII bit, which caused certain decimal instructions to behave a little differently with regard to the sign nybble. If your 360 program depended on that, it would not work correctly. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
