Question

Registers R4 and R5 contain the decimal numbers 200 and 500 before each of the following addressing modes is used to access a memory operand.

What is the effective address (EA) in each mode when operands are accessed?
a. 8(R4)
b. 19(R4,R5)
c. (R4)+
d. -(R5)

Answer 1

The effective addresses for different addressing modes are 208, 719, 200, and -500 respectively.

Step-by-step explanation:

a. For the addressing mode 8(R4), the effective address (EA) is obtained by adding the value in R4 (200) with the offset 8. The effective address would be 208.

b. In the addressing mode 19(R4, R5), the effective address (EA) is obtained by adding the value in R4 (200) with the value in R5 (500) and the offset 19. The effective address would be 719.

c. In the addressing mode (R4)+, the effective address (EA) is obtained by using the value in R4 (200) directly. The effective address would be 200.

d. For the addressing mode -(R5), the effective address (EA) is obtained by subtracting the value in R5 (500) from the offset. The effective address would be -500.