In the Dark Old Days, there was more specialization, so you could (and were expected to) become deeply knowledgeable about a few things, e.g. Cobol programming

In the Dark Old Days, there was more specialization, so you could (and were expected to) become deeply knowledgeable about a few things, e.g. Cobol programming on OS/360. The computer vendor usually supplied everything, including the OS and the one language you used, and decent manuals were expected.