Invoking a Resident Program From the Keyboard of the IBM Personal Computer
Original Publication Date: 1985-May-01
Included in the Prior Art Database: 2005-Feb-18
A method to invoke a resident program from the keyboard of the IBM Personal Computer (PC) is described. An Interrupt 5 (I5) is issued from the keyboard handling code when the "Shift-PrtSc" (SPS) key combination is detected. Normally, in the PC this causes the print screen function to be invoked. A resident program is capable of being invoked from the keyboard by having the resident program replace the normal I5 vector with a vector that points to an interrupt handler in the resident program. The I5 handler contains logic to properly back the system out of the keyboard handler by popping the stack registers a variable number of times, depending on the code employed in the particular PC model. A resident Debug Facility may be invoked in this manner.