Question

The interrupt vector for each interrupt type in 8086 microprocessor requires___ memory locations

• A. One
• B. Two
• C. Three
• D. Four

Hint:

The 8086 Interrupt Vector Table (IVT) stores pointers to Interrupt Service Routines (ISRs).
Each pointer (interrupt vector) is 4 bytes long: 2 bytes for IP (offset) and 2 bytes for CS (segment).
The IVT can hold up to 256 such vectors.

Answer 1

The Correct Option is D

In the 8086 microprocessor, the Interrupt Vector Table (IVT) resides in the first 1KB of memory (addresses 00000H to 003FFH). This table stores the starting addresses of the Interrupt Service Routines (ISRs) for different interrupt types. Each interrupt type is assigned a unique number (from 0 to 255). For each interrupt type, the IVT stores a 4-byte address:
2 bytes for the new Instruction Pointer (IP) value (offset address of ISR).
2 bytes for the new Code Segment (CS) register value (segment address of ISR). These 4 bytes (IP low, IP high, CS low, CS high) specify the full 20-bit starting address of the ISR. Therefore, each interrupt vector (pointer to an ISR) requires 4 memory locations (bytes). \[ \boxed{\text{Four}} \]