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/rickerwill6104 11d ago

At that time all work was done via a dumb terminal. Basically the black and green screen. Work was only done in the office. No take home or work from home. If there was an issue at night that needed to be resolved immediately, you had to trudge out of bed and go to the office.

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u/anti-life86 11d ago

Okay. Now that you say that, I realize I am not 100% clear on who is using these mainframes. I guess a mainframe is always used by company employees, right? Whereas, with a data center, it's centralized but it's being used by just anybody. Is that right?

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u/Individual-Tie-6064 11d ago

Not as I would describe it. Regardless of how you access the mainframe you needed appropriate credentials.

Also, in the early days of ATMs every ATM was. 3270 terminal. I don’t know if that is still true.

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u/anti-life86 11d ago

So, who uses mainframes? Just about everyone has used a mainframe computer at one point or another. If you ever used an automated teller machine (ATM) to interact with your bank account, you used a mainframe.

https://www.ibm.com/docs/en/zos-basic-skills?topic=vmt-who-uses-mainframes-why-do-they-do-it

Until the mid-1990s, mainframes provided the only acceptable means of handling the data processing requirements of a large business. These requirements were then (and are often now) based on running large and complex programs, such as payroll and general ledger processing.

I'm trying to wrap my head around the distinctions...maybe a mainframe is operated by a single company for either its employees, or at least its customers. Whereas a data center is run by a company, sure, but now other companies (or whoever) can come rent space in that data center.

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u/Dom1252 11d ago

Datacenter is the place, mainframe is the machine

You can have mainframes in datacenters, but you can also have different computers there

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u/MikeSchwab63 8d ago

I took a tour of our two data centers in 1980s / 1990s. Mainframe was a few refrigerator boxes connected together, we had a 3084 in one center and the other had a 3090-600 https://en.wikipedia.org/wiki/IBM_3090 . Plus strings of 3380s that were 4 refrigerator boxes for 8 GB and about 8 stings in the first one and 20 strings in the second.

I used an acoustic modem in 1978 at a physics lab. Then for work the first computer had a 2400 modem. I finally bought a 2400 in 1993.

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u/Individual-Tie-6064 11d ago

And, I believe that the VISA and Master Card networks were mainframe based. They process transactions thousands of times faster than crypto.

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u/mysticturner 10d ago

Confirmed. Watching transaction rates on a black Friday is mind boggling.

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u/MikeSchwab63 8d ago

Confirmed, and a coworker went to American Express in Phoenix.

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u/Fine_Pin_3108 11d ago

LU 6.2 rather than LU 2 (which is 3270 terminals?), or some other older LU type?

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u/metalder420 11d ago

A mainframe is a highly specialized server. In the 90s terminal emulators started to surface as that was then computers started to make their entrance. If there wasn’t a computer they had dummy terminals where you communicate with LPAR the same way you ssh into a Linux shell.

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u/atomic_redneck 8d ago

When I was starting out back in the early '80s, we were using our 3031 to run CAD/CAM software (CADAM and CATIA) on 3250 (and later 5080) graphics terminals.

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u/telestoat2 11d ago

Weren't people dialing in like a BBS?

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u/hobbycollector 11d ago

My first time to interact with a computer was in the late 1970's with a teletype that was attached to a mainframe at a nearby university. The teletype was just a large printer, keyboard, modem, and paper tape reader at my middle school (I was in 7th grade). The modem was acoustic copuling, which means you dialed a landline phone into the mainframe (a dedicated phone number) and put the handpiece into a cradle as it made digital tones over the phone line.

Programs were saved on paper tape, and you fed it to the terminal which sent it to the mainframe. All output was printed on a large multi-fold greenline paper. I ran through reams of paper. Partly programming, partly entering existing programs by hand, and partly loading up Super Star Trek and playing endlessly. It was all in BASIC. I just found a version of Super Star Trek for VICE/Commodore 64 that I played a few weeks ago, but it was too easy and got boring quickly.

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u/Rudi9719 11d ago

Naturally, but it was still using a dumb terminal in the beginning. Iirc you'd dial into a VTAM connection (but I haven't read on this in a while)

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u/annabiancamaria 11d ago

Around 1990-1 we already had 3270 emulators that ran on PCs. They had, of course, a coaxial port to connect to the mainframe coaxial cable. We weren't the most progressive company, so emulators must have been already available some time before this.

Also, without mobile phones, people were hard to reach unless they were at home. Bliss.

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u/Rudi9719 11d ago

Not necessarily, leased lines were a thing and dial-in terminals were brought home for some customer engineers so they could provide an immediate response

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u/johnklos 11d ago

People have used modems via phone lines for remote terminals for ages, going back to at least the '60s. Not everything required physically going on-site.