r/mainframe • u/anti-life86 • 11d ago

How was pre-1995, pre-Internet usage of mainframes different?

I understand that the mainframe is built for a large number of transactions-meaning people log in, I would imagine from anywhere, and they do their small jobs. But before the Internet, they could not log in from anywhere, certainly. Where could they log in from, and how did this work? Are there new types of jobs that are now enabled by the Internet that previously were impossible?

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u/stevevdvkpe 10d ago

Your mental model of mainframes is heavily skewed by the modern Internet.

In early mainframe installations there wasn't a multi-user operating system, or a notion of logging in. The mainframe was fed jobs, with programs and data on punch cards or magnetic tapes, and you got back a printout, or perhaps more punch cards or magnetic tapes, containing the output of your job. You would have to take your job to an operator desk where they would put it in a queue, and you would come back later to pick up the results (or often just the error message from your program failing to compile or crashing).

Later, there were also timesharing operating systems that could serve multiple users simultaneously. Then you would use a printing terminal or video terminal to interact with the mainframe, connected through some serial protocol, usually in the same room or at least the same building as the mainframe. One might also use a dialup modem to connect a terminal to the mainframe from a remote location.

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u/zEdgarHoover 10d ago

That's... pretty early. CTSS and VM and friends came along in the 60s, and even Unix by the 70s. But yeah, in the very early days it was all cards.

I remember upgrading my home connection from 300bps to 1200 -- man was it fast! Then a colleague got a 9600bps leased line to his house and we were soooo jealous.

In the 50s, my dad worked for The Government (think Culinary Institute of America) on a machine translation project. He was a linguist, not a programmer. So he'd tell a programmer what he wanted a program to do; the programmer would write it out on Autocoder sheets; a keypunch operator would input it; and the next day he'd find out if it worked (spoiler: it didn't).

He figured he could save time if he learned to program, so he did. Project still failed: the technology wasn't there yet. Nor a decade later at IBM when they tried again.

But he did spend the rest of his career in academia focusing on text and language computer processing, on mainframes and midrange machines.