probably a most featureful replacement ROM for ZX Spectrum 48k,
which features many bugfixes, arrows up/down in command-line editing, 
line numbers from 0 to 16383, POKE with unlimited number of byte, 
word and string arguments 
(like POKE 50000, 33;16384,1;6144,201,"test";USR(50000)), 
jump to the position of error on the line, various other 
little improvements, and a small disassembler (using SYS *address, 
SYS is a replacement for COPY). 
[ROM code (c) Amstrad ltd., changes (c) Milan Pikula]