h6. [[OS SWI Calls]] h6(. » [[OS_Byte]] h6((. » OS_Byte 218 h2. OS_Byte 218 h5. (SWI &06) |_<^{width:4em}. Entry | | |<^. R0|<^. 218 (&DA) | |<^. R1|<^. EOR value | |<^. R2|<^. AND value | |_<^{width:4em}. Exit|_<^. | |<^. R0|<^. Preserved | |<^. R1|<^. Previous count | |<^. R2|<^. Corrupted | h4. Use The purpose of this call is to read or write the count of bytes in the VDU queue. h4. Notes The value of the count is -(bytes needed to complete [[VDU Codes|VDU sequence]]) held in 1 byte, so if two bytes are needed to complete the current sequence then count will be &FE. Usually this call is used to set the count to 0, which abandons any current VDU sequence. This stops error messages being garbled by a partially completed VDU sequence. h4. See also * [[OS_Byte]] * [[VDU Codes]]