This is ZXDS – Sinclair ZX Spectrum emulator for Nintendo DS coded by Patrik Rak.

For quick install, simply copy the entire ZXDS directory to the root of your card, then run ZXDS.nds as you run any other application. For more detailed documentation, usage instructions and updates, please go to http://zxds.raxoft.cz

ZXDS 0.7.0 beta 1 (21.12.2007)

+ Finally added keyboard graphics, for both 48k and 128k keyboard.
+ Replaced the ad-hoc file requester with proper touch screen version.
+ Configurable button to key/action binding, with 9 predefined customizable settings.
+ Tape browser and manual tape control.
+ Autoload feature, with both tape-loader and USR0 mode support.
+ Skinning support for changing graphics and color of each UI element.
+ Builtin online help.
+ Pentagon emulation (no TR-DOS yet, though).
+ Z80 snapshots are now compressed.
* Added 1 forgotten T state to EX (SP),* instructions.
* Fixed #7FFD paging decoding (A15+A1 instead of A14-15+A1), more demos now work.
* Changed #1F kempston joystick decoding (loose A5 instead of strict A5-A7), more games should work.
* Disable autoplay when tape end is reached, more flawed tape files should now load.
* Few other subtle fixes (triple buffering race, halt timing upon requester).

http://zxds.raxoft.cz/