The ZX81 was a small black wedge with a flat, touch-sensitive membrane keyboard. It sold for £69.95 ready-built, or £49.95 as a kit to solder together, and for many British families it was the first computer in the house.
Its four chips kept it cheap. The processor did the work of drawing the screen too, so in FAST mode the picture blanked out while programs ran. The 16 KB RAM pack was famous for wobbling loose and wiping your work.
No pixels as such: only black and white text characters, 32 across and 24 down. Pictures were built from graphics characters, each cell split into four blocks, which gave a grid of 64x48 chunky blocks plus a chequered grey.
None at all. The machine was silent, though some owners got tones from it by abusing the video signal or the cassette port.