INT is an assembly language instruction for x86 processors that generates a software interrupt.
It is therefore entirely possible to use a far-call instruction to start the interrupt-function manually after pushing the flag register.
By calling it with different parameters in the registers (mostly ah and al) you could access various IO operations, string output and more.
This is accomplished by entering a 32-bit value corresponding to a kernel function into the EAX register of the processor and then executing INT 0x80.
It is a conditional interrupt which is triggered when the overflow flag is set at the time of executing this opcode.