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I've written Windows software in C++ for more than 10 years, and I've compiled as recently as 6 months ago software that was written in the early 1990's, and th

by roel_v 14y ago

btilly 14y ago
I've written Windows software in C++ for more than 10 years, and I've compiled as recently as 6 months ago software that was written in the early 1990's, and that would compile and run unmodified on today's OS's. Show me one platform (or library even) that has that sort of backward compatibility. Challenge accepted. IBM shipped the first iteration of the System/360 in 1966. They have maintained, with minor caveats, backwards application compatibility with that version to the present across their various mainframe lines. As an example of such a caveat, in 1995 the AS400 line underwent the 48-bit to 64-bit transition. If your executable was "observable", meaning it had debugging information, the first time you ran in 64-bit mode IBM would recompile it under the hood and your software would then run in 64-bit mode. If you had no source and no debugging information in your executable, you were out of luck until you got a new executable. Most customers experienced no issues. But..mainframes? Who uses those? A lot of people, it turns out. A 2005 estimate said that globally 90% of financial transactions ran through COBOL. There is no reason to believe that this figure is significantly reduced today. The core of most of that COBOL code is decades old, and the customers are locked to IBM's platform because nobody can afford the cost or risk of a rewrite. But machines need to be replaced. Therefore IBM's customers still collectively cough up an average of something like $1 billion/month on new mainframe hardware.

by roel_v 14y ago

btilly 14y ago

I've written Windows software in C++ for more than 10 years, and I've compiled as recently as 6 months ago software that was written in the early 1990's, and that would compile and run unmodified on today's OS's. Show me one platform (or library even) that has that sort of backward compatibility. Challenge accepted. IBM shipped the first iteration of the System/360 in 1966. They have maintained, with minor caveats, backwards application compatibility with that version to the present across their various mainframe lines. As an example of such a caveat, in 1995 the AS400 line underwent the 48-bit to 64-bit transition. If your executable was "observable", meaning it had debugging information, the first time you ran in 64-bit mode IBM would recompile it under the hood and your software would then run in 64-bit mode. If you had no source and no debugging information in your executable, you were out of luck until you got a new executable. Most customers experienced no issues. But..mainframes? Who uses those? A lot of people, it turns out. A 2005 estimate said that globally 90% of financial transactions ran through COBOL. There is no reason to believe that this figure is significantly reduced today. The core of most of that COBOL code is decades old, and the customers are locked to IBM's platform because nobody can afford the cost or risk of a rewrite. But machines need to be replaced. Therefore IBM's customers still collectively cough up an average of something like $1 billion/month on new mainframe hardware.