[Someone]

IIRC, graphics used 2x2 block characters. With 24 lines of 32 characters, that would give you 64x48.

However, video memory ate into your 1k RAM. At 24 lines of 32 characters, a conventional video memory would need 75% of that 1k bytes, so they did things differently; video memory was laid out as you would do in a text editor, with each line ending in a line separator character.

That way, an empty screen took just 24 bytes, a full one (32x24) + 24 = 792 bytes, leaving 232 bytes for a program.

=> few programs for the 1k version could use the full screen.

[pascal_cuoq]

You are correct, but the screen's last two lines of text required some tricks to take advantage of (search for “reserved” in http://www.tebbo.com/archive/pw810601.htm ), so “64x44” is also a correct description from the programmer's point of view.

The particular trick that enabled the program to use the last two lines was easy to come by (I was in the countryside, hundreds of kilometers from the nearest user group, and I only had a few books as source of information). The existence of such tricks, including the pure software “hi-res” more that I read about at the time but didn't get to see until the Internet made it possible 12 years later, is one of my fond memories of that era.

[rwmj]

Also the reason why 1K Chess occupied the left hand side of the screen. That way it needed much less video RAM. Screenshot: http://www.retrogamer.net/wp-content/uploads/2014/02/1k-zx-c...

[FabHK]

I remember implementing the Mandelbrot set ("Apfelmännchen"), and it would plot one of those "pixels" every few seconds, so the whole thing only took a few hours :-)