Is top-left-corner for VT100 0,0 or 1,1?

Question

I wrote/maintain a terminal emulator called ucon (http://www.umonfw.com/ucon). I suppose calling it an actual terminal emulator is sad because although it does a lot of good stuff, its not very good at dealing with the VT100 escape sequences. Anyway, one issue I've never resolved is the actual coordinate position of the top-left-corner (TLC). For quite some time now I've assumed that 1,1 is the TLC (that's what VI seems to use); however, there are several cases where it appears that 0,0 is the TLC. Plus I do occasionally see programs actually use the escape sequence "<1b>[0;0f" which forces the cursor to position 0,0; hence, if we assume the cursor is not intentionally being placed off screen, one would have to assume that 0,0 is the TLC.... ????

Anyone out there a VT100 guru?

Answer 1

The top left corner is 1,1 according the ANSI X3.64 standard. The value of zero represents the default value. And the TLC is the default in this case.