INT 07H is executed automatically when any 80x87 Floating Point Opcodes are executed and no math chip is there to handle it. More generally, this takes place when an ESC or WAIT opcode is executed specifying a coprocessor that's not present. Math chip emulators intercept this interrupt to provide floating-point support (very slowly, I might add). See Also: IRQs (hardware interrupts) ROM-BIOS Functions DOS Functions -♦-