Gate CS-2015-2 Question Paper With Solutions

Q. 48 Consider a processor with byte-addressable memory. Assume that all registers, including Program Counter (PC) and Program Status Word (PSW), are of size 2 bytes. A stack in the main memory is implemented from memory location (0100)₁₆ and it grows upward. The stack pointer (SP) points to the top element of the stack. The current value of SP is (016E)₁₆. The CALL instruction is of two words, the first word is the op-code and the second word is the starting address of the subroutine (one word = 2 bytes). The CALL instruction is implemented as follows:

   • Store the current value of PC in the stack.
   • Store the value of PSW register in the stack.
   • Load the starting address of the subroutine in PC.

The content of PC just before the fetch of a CALL instruction is (5FA0)₁₆. After execution of the CALL instruction, the value of the stack pointer is

(A) (016A)₁₆

(B) (016C)₁₆

(C) (0170)₁₆

(D) (0172)₁₆

Answer: (D)

Explanation: