When calling the OSBPUT routine from machine code you will need to use the absolute address &40D4. However, when CALLing this routine from BBC BASIC it is recommended that you use the BBC Micro-compatible address &FFD4.

A routine which writes a byte to an open file via its handle. The file pointer is incremented after the byte has been written. This routine performs the same task as the BPUT# statement.

On entry, H contains the file handle and A contains the value to write to the file.