Is there a way to convert the c51 compiler so I can write programs on my mobile phone (a galaxy s2) and then download them onto the atmel at89s51 mcu?
Of course, it is easier to use MS-DOS tools, since there are several good MS-DOS emulators available for Android. Then it's just a question of installing Turbo Pascal, classical games or whatever and enjoy.
An interesting problem - how to connect peripherial equipment to the emulated PC running inside the Android phone.