The computer used memory slots for RAM expansion, removable mass storage and proprietary program use, although one might have some liberty for which purpose of these, the three slots were used. Since the slots genuinely did use RAM, EPROM and ROM for their data transfer, the transfer speeds were usually very high, but the maximum storage afforded by any one such card, correspondingly low and expensive to boot.
Though the display had only 8 lines, the user manual claimed that it was only printing the "center lines" for "convenience" of the user reading the manual. A similar kafkaesque subterfuge extended to the display itself. When displaying a wordprocessor function or its native VT52-type terminal, it wasted one line to display a square image of an "imaginary" full screen, which supposedly contained a computer screen, of which the current 7 lines were merely a limited view.
The Z88 was designed by Sir Clive Sinclair and released by his company Cambridge Computers in 1987 (Sir Clive having been bereft of the right to market the computer as the Sinclair Z88 after selling Sinclair Research's computer business to Amstrad in 1986).