You would color in the squares on graph paper. And then after you coloured those individual squares, you would convert them in to numbers, and then you would ke

You would color in the squares on graph paper. And then after you coloured those individual squares, you would convert them in to numbers, and then you would key in the numbers in hexadecimal using a ROM writer I used to do this on the BBC Model B, you could re-program character codes to be any shape and would use that to build up graphics. It was really exciting when the thing you'd drawn on paper finally appeared on screen. Or if you'd made a mistake with the hex, there would be pixels or (often) horizontal lines in the wrong place on a row.