icebp

INT1 and INT3 are short one-byte forms of the instructions INT 1 and INT 3 (see INT). They perform a similar function to their longer counterparts, but take up less code space. They are used as breakpoints by debuggers.

• INT1, and its alternative synonyms INT01 and ICEBP, is an instruction used by in-circuit emulators (ICEs). It is present, though not documented, on some processors down to the 286, but is only documented for the Pentium Pro. INT3 is the instruction normally used as a breakpoint by debuggers.

• INT3, and its synonym INT03, is not precisely equivalent to INT 3: the short form, since it is designed to be used as a breakpoint, bypasses the normal IOPL checks in virtual-8086 mode, and also does not go through interrupt redirection.