Win 3.1 wins this because it was around that time that PCs became more accessible. The prices started to get down to where Mr-slightly -above-average-income could afford them.
But if you want know who's an old fart - I started programming in FORTRAN on coding sheets that then had to be converted and entered into the computer memory using coding switches and an "enter" button.
Then I moved onto punch-cards and then a terminal. I eventually learned BASIC on a SuperBoard and later a ZX80. MY first pc (lower case) experience was an Apple IIe witha green screen and my first IBM compatible was a 286 with Win 3.1 on a colour monitor.
Those were the days.
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