Almost any of the music score programs discussed in recent threads include an onscreen "keyboard" as an input method. You use your mouse to click a key on what looks like a little piano keyboard, and the note appears on the staff. You do have to select a "time value" for the note, quarter, half, etc.

Most of these programs are MIDI capable, and with almost any soundcard with a MIDI input, you can plug a keyboard in and "play" a piece into the program. Results are varied, depending on your playing skill (and sometimes on arcane settings in the program) since it will "write" exactly what you play - which sometimes doesn't look very pretty.

Most of these same programs allow you to "equate" PC keyboard keys to the piano keyboard. Several I've looked at use a small section of the keyboard and you run a scale by playing adjacent keys; others use a, b, c, d, etc. For most, number keys select "durations" 1=whole, 2=half, 3=quarter note etc, or sometimes the reverse.

Again - almost any score writing (or MIDI mangling) program of decent quality will probably do what you asked for.

John