True, but you could also get the address of the screen buffer and define a structured type to overlayed it that allowed you to put values directly into memory.

Each screen location was two bytes, one byte for the character value, and one for the character attributes which were a set of bits that controlled red, green, blue and intensity for both the foreground color and background color.

Then you could write routines that would fill in a rectangular region with a color, scroll the text of a region up or down, and do all sorts of other windowy things. There were also interrupt routines you could call that did some of these, and certainly routines in Crt that did some of this. Then you were on your way to developing your own TUI library!

Alternatively, you would issue an interrupt call to put the screen into 320x200 256 color mode, get the address of that buffer ($B800 if memory serves), similarly overlay it with a typed grid, then start poking byte values in and getting all sorts of nice colors out of it. Super fun!!