Re: Old update files
Worth compressing? Probably not.
On DOS and Win16, when you loaded a program, the executables were opened, read, unpacked, patched, yawn, have I forgotten anything, and then used. It was likely that most of the file was read and so compression reduced the amount of raw file I/O.
On Win32 and pretty much any OS from the last quarter century, the executables would simply be memory mapped and paged in as necessary, so if you only refer to a handful of functions in a large DLL, most of the file is never touched. If you compress your program files, however, the whole file needs to be read and decompressed before the handful of pages you were interested in can actually be used.
Given Windows' propensity for having (unused) references to DLLs that in turn have unused references to other DLLs, compression is probably a substantial net loss.
But I haven't made any measurements, so I'm talking out of my behind.