I was wondering who invented the blinking of a cursor, because I was just thinking if it wouldn't blink the UI would be a lot less responsive.. so this must have been one of the first signs of response UI design. Was this IBM? I'm to young to make guesses though.
Or if this question would be impossible to answer, what is the first sign of a blinking cursor in computer history.
According to that, it was invented by Charles A. Kiesling at Sperry Rand. Patent filed Aug 24, 1967, granted Sep 29, 1970. This isn't iron clad proof that it was first invented at that time, but the time seems about right (computers were getting powerful enough that engineers were starting to care a little bit about user convenience) and Sperry Rand was one of the big players in computing at the time.
Simple answer, it was Charles A. Kiesling Sr. He was my father and he did indeed write the code for the blinking cursor when he worked at Sperry. He passed away yesterday in Minneapolis at the age of 83. I remember him telling me the reason behind the blinking courser and it was simple. It was not because it looked like an "I". He said there was nothing on the screen to let you know where the courser was in the first place. So, he wrote up the code for it so he would know where he was ready to type on the Cathode Ray Tube. It ties in with this patent for the display stuff he put together for the screens back in the day. http://www.google.com/patents/US3497760
And a foot note to this, he was not happy when the first Apple computers came out and they had is _ blinking on the screen. Since he worked for the company, he let Sperry deal with it as he wrote the code for Sperry.