Working 16K, 48K, 128K, +2, +2A, +3, +3e, SE, TC2048, TC2068, Pentagon 128 and Scorpion ZS 256 emulation, running at true Speccy speed on any computer you're likely to try it on.
The best for Windows. Shareware (last free version: 5.21). It emulates the 16K/48K/128/+2/+2A/+3 Spectrums, the Russian Pentagon 128 and Scorpion ZS256 clones, and lots of additional hardware.
Its basic characteristics is so large reduced it is, about 4Kb. The main objective is to occupy the minimum space of hard disk possible and to offer a totally trustworthy emulation in speed, graphs and sound.
It's a ZX Spectrum emulator written entirely in Assembler. It runs under MS-DOS and it's the only one that emulates the Inves Spectrum + (a Spanish clone)
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INFORMATION
Don't you know what it is an emulator? It's simple: an emulator is a program that let you run games and programs of your old computers into the modern PCs, Macs, mobile phones and new generation consoles. You could load the images of those games, whose are available for thousands in Internet.