Question

Which one of the following references to memory is illegal and causing a trap to the operating system? Please refer to the following picture on Page 341 (Figure 7.9) subroutine stack 1400 segment 3 ment 2400 symbol table segment o limit base 0 1000 1400 1400 6300 2 400 4300 3 1100 3200 4 100O 4700 rt segment 4 3200 main program egment segment table ment 1 segment 2 4700 egment logical address space segment 4 5700 6300 670 Segment 1 physical memory Reference to byte 53 of segment 2 Logical address 5600 from segment 4 Logical address 4052 from segment 3 Reference to byte 1222 of segment 0

Answer 1

Byte 53 implies 53*8 = 424. The base address for segment 2 is 4300. Thus when we are trying to access the 53rd byte of segment 2, we are in effect trying to access 424+4300 = 4724. 4724 is not there in segment 2. Hence, it will cause a trap to the operating system.