AH = 59h BX = 00 for versions 3.0, 3.1, 3.2 on return: AX = extended error code (see DOS ERROR CODES) = 0 if no error BH = error class BL = suggested action CH = locus - may be called after any INT 21 function or from INT 24 when an error is returned - must be called immediately after the error occurs - registers CX, DX, DI, SI, BP, DS and ES are destroyed