Exams › GATE › Technical

Suppose a program is running on a non-pipelined single processor computer system. The computer is connected to an external device that can interrupt the processor asynchronously. The processor needs to execute the interrupt service routine (ISR) to serve this interrupt. The following steps (not necessarily in order) are taken by the processor when the interrupt arrives: (i) The processor saves the content of the program counter. (ii) The program counter is loaded with the start address of the ISR. (iii) The processor finishes the present instruction. Which ONE of the following is the CORRECT sequence of steps?

1. (iii), (i), (ii)
2. (i), (iii), (ii)
3. (i), (ii), (iii)
4. (ii), (i), (iii)

Correct answer: (iii), (i), (ii)

Solution

The correct sequence is (iii), (i), (ii) because the processor must first complete the current instruction to ensure data integrity, then save the program counter to remember where to return after handling the interrupt, and finally load the program counter with the ISR's address to begin executing the interrupt service routine.

Related GATE Technical questions

• Which ONE of the following statements is FALSE regarding the symbol table?
• Which ONE of the following techniques used in compiler code optimization uses live variable analysis?
• Consider a demand paging memory management system with 32-bit logical address, 20-bit physical address, and page size of 2048 bytes. Assuming that the memory is byte addressable, what is the maximum number of entries in the page table?
• A schedule of three database transactions T1, T2, and T3 is shown. Ri(A) and Wi(A) denote read and write of data item A by transaction Ti, i = 1,2,3. The transaction T1 aborts at the end. Which other transaction(s) will be required to be rolled back? R1(X) W1(Y) R2(X) R2(Y) R3(Y) ABORT(T1)
• Identify the ONE CORRECT matching between the OSI layers and their corresponding functionalities as shown. OSI Layers — Functionalities (a) Network layer — (I) Packet routing (b) Transport layer — (II) Framing and error handling (c) Datalink layer — (III) Host to host communication
• Let G be any undirected graph with positive edge weights, and T be a minimum spanning tree of G. For any two vertices, u and v, let d1(u,v) and d2(u,v) be the shortest distances between u and v in G and T, respectively. Which ONE of the options is CORRECT for all possible G, T, and v?

⚔️ Practice GATE Technical free + battle 1v1 →