setchar( <x>, <y>, <c> )


This sets the specified character location ('x' = 1 to 40, 'y' = 1 to 25) to the specified character value ('c' = 0 to 255).


You can use the set <var> to char(<x>, <y>) command to read the value of a given character, the logical opposite of setchar().


RISC OS: There is a macro that states if a null byte (value = 0) is encountered when exporting the file as ASCII, then the sequence <10><32> will be output. This is supposed to write a newline followed by a space, however it seems to output a newline too many and I've not gotten around to fixing this.
The space, incidentally, is so you can replace a colour code (which would be converted to a space) with this macro, and preserve text alignment.

Windows: The null byte behaviour is not supported.