On Mon, Jan 22, 2024 at 07:11 PM, Tony Harminc wrote:
Assembler F and XF are indeed completely different programs. For whatever reasons, IBM appears to have written XF to the same specs as F, but from scratch. There are a few minor new features, and the code is reentrant (whoop-de-do), but that's it. That notwithstanding that the vastly superior Assembler H already existed.
Remember, the suffixes for various products is not based on function level but how much (real) memory it needed; this was an era when the IBM S/360 65 maxed out at 1 MB core of fast core.? Even the S/370 model 165 was originally offered with only up to 3 MB of core.? (The way Hercules users can run MVT on a uniprocessor with 16 MB of cheap real memory was a fantasy in 1971.)
Quoting Wikipedia:
Between 1966 and 1968, IBM offered several FORTRAN IV compilers for its System/360, each named by letters that indicated the minimum amount of memory the compiler needed to run. The letters (F, G, H) matched the codes used with System/360 model numbers to indicate memory size, each letter increment being a factor of two larger:?
- 1966 : FORTRAN IV F for DOS/360 (64K bytes)
- 1966 : FORTRAN IV G for OS/360 (128K bytes)
- 1968 : FORTRAN IV H for OS/360 (256K bytes)
Function was certainly related to how much memory was needed, but (re)writing an F level component when the H component existed made perfect sense if the F level component needed a quarter of the??(expensive)?memory.
Weird but true.?
No, just pragmatic.
-ahd-
--
Drew Derbyshire
Software Hobbit (SRE Emeritus)
