Discuss all the five software interrupt instructions.

The INTEL family microprocessor consist of software interrupts INT, INT0, INT3 and BOUND and IRET. Out of all these five interrupts INT and INT3 are very same, BOUND and INT0 are conditional type, and another one IRET is special interrupt return instruction.

The BOUND instruction that has two operands that is compares a register with two words of memory data.

INT0 instruction checks there overflow flag (OF). If OF=1, the INT0 instruction calls this procedure whose address is stored into interrupt vector form, number 4. When OF=0, then the INT0 instruction performs no operation and subsequent sequential instruction in the program executes.

There INT n instruction calls the interrupt service procedure which begins at the address represented in vector number n. For illustration, an INT 80H or INT 128 calls the interrupt service procedure that address is stored in vector type 80H (000200H - 000203H). To find out the vector address, only multiply the vector number (n) by 4 that gives the beginning address of the 4-byte long interrupt vector. For illustration: an INT 5 = 4 x 5 = 20 (14H). The vector for INT5 begins at address 000014H and persists to 000017H. The only exception is the INT3 instruction, a 1-byte instruction.

The IRET instruction is a special return instruction utilized to return for both software and hardware interrupts. The IRET instruction is same like a RET, since it retrieves the return address from the stack.