Well,you asked ...
(I've been nervous about posting here since my first contact with a computer was probably before most people in here were born!)
Anyway, it was in 1965 and was with a mainframe computer called the Honeywell 200 (H-200) - a competitor to the IBM 1401. (See photo.)
Specifically, my first contact was with the tape drives. (These are the tall machines with wheels on them at the back of the photo - some of the installations had up to 16 of them.) My job was to commission them as they came off the production line in the factory. A fairly accurate demonstration of how an H-200 program (nowadays called an "app", it seems!) would be started up is in the movie "The Billion Dollar Brain", viewable on YouTube at:
The actor, Karl Malden, shows the fairly tricky process of loading a tape into a drive.
The first computer I owned was a Sinclair QL - in 1984.
I bought it because IBM PCs were starting to appear on the desks of the clients I was supposed to be doing IT consulting for, and I knew nothing about the things. I asked my boss to buy a PC for the office - for learning purposes - but he refused (they cost about 4000 GBP at the time). So I bought myself a QL, since it had most of the functionality of an early PC at a tenth of the price, and learned about word processing, spreadsheets and more on it. (The QL was not a commercial success, its failure being blamed on the unreliability of its microdrives. However, I experienced few problems with them.)
(An anecdote: the Honeywell factory once had an open day and I took my young brother along to see the machine I was currently building. Later in life, as a teacher, he had great delight in telling his class that he once walked through a computer. Naturally, they couldn't believe him.)
After getting involved in various industrial control computer in the course of my career, I am now happily surrounded by a PC or two and a bevvy of Raspberry PI's (which I can't walk through!)
(Well, you did
IT Background: Honeywell H2000 ... CA Naked Mini ... Sinclair QL ... WinTel ... Linux ... Raspberry Pi.