the user moves the hardware cursor to the text to be read and the OS displays a second cursor in software at the original position. Pressing copies one character from the hardware cursor to the software cursor and advances both, so that holding the key down copies a section of the text, the cursors wrapping around the vertical edges of the screen as necessary. If the screen scrolls during editing, the hardware cursor's position is adjusted to follow the text. The user can make changes to the text during the copy, and user-defined characters are recognised in graphics modes. Screen editing is terminated when or are pressed, which have their usual effects. Character recognition is made available to users in the API with a call to read the character at the current cursor position. Sound Sound generation is carried out through another OS call, OSWORD, which handles a variety of tasks enumerated via a task code placed into the accumulator. All OSWORD calls bear a parameter block used to send and receive multiple data; the address of this block is passed in the X and Y registers, with the low byte in X and the high byte in Y. There are four buffered sound channels three melodic and one noise-based on the sound chip found in the BBC Micro. There is only one waveform for melodic channels; the supported note parameters are pitch, duration, amplitude, envelope selection and various control options. For the amplitude parameter, a zero or negative sets a static amplitude, and a positive value select an amplitude and pitch envelope (a predefined temporal variation) to apply to the note. Control parameters was passed through the channel parameter, and include flush (the buffer is cleared and the channel silenced before the note is played), synchronise count (as soon as the same sync count is received for that many channels, all the synchronised notes are played together), and control over the Speech system upgrade where fitted. OSWORD handles many functions other than sound, many of which do not have direct support in BASIC. They may be accessed from BASIC by setting up the parameter block, loading its address into X% and Y% and the task code into A%, and then calling the routine. Other I/O and second processor support The BBC Micro had support for a second processor connected via the Tube, which allowed direct access to the system