[altair]

I haven’t seen this addressed anywhere: How long has the number 7 typically had a line through it to insure that it is read as a seven and not something else? I notice this in the BC application number. How far back does this practice go?

Good question. It goes a long ways back, well before OCR. I picked it up in the early 70s when I was first being taught computers. Its usage was typical in the computer books of that time, so I guess it goes back much farther than that.

[RetroSexual]

I haven’t seen this addressed anywhere: How long has the number 7 typically had a line through it to insure that it is read as a seven and not something else? I notice this in the BC application number. How far back does this practice go?

Good question. It goes a long ways back, well before OCR. I picked it up in the early 70s when I was first being taught computers. Its usage was typical in the computer books of that time, so I guess it goes back much farther than that.

Although I was raised in the midwest, I had a German math teacher in the '70s who literally would rap your knuckles with a ruler if he saw you making a 7 without a slash through it. So my impression is that it's a continental European thing.

The other memory I have of him was that he had a wandering glass eye. You never could tell if he was looking (or even speaking) to you or to some other kid across the room.

He and I never got along very well, but you know what? I love math to this day. So I guess the old psycho was good at his job.

[cookcounty]

The 7 with a line thru it is pretty old practice in Europe, where they write “1” with a very long front stroke, making it look almost like an inverted “V”, and therefore easily confused with “7”. The line through the “7” distinguishes it from a long front stroke “1”

[Steven Tyler]

I was not taught to add a horizontal line thru my “7”.
My parents, and later older European co-workers, always added this line to their “7”