Quiz 11.3

DIRECTIONS: Read each question carefully. Then click on the dot next to the answer that most closely fits the question. Try to answer all questions on this quiz and when you are done, click on the grade me button at the bottom.

Coverage: Section 11.5

  1. An errant (faulty) program can overwrite some data and instructions in memory but not others. Which cannot be harmed?
those in lower memory than this program
those in higher memory than this program
there is no safe area in memory

  1. Which method of protection is used by some IBM mainframes?
base address and field length registers
keys and banks

  1. What is a downside of use keys and memory banks?
a malicious program is able to change its own key at run-time thereby gaining access to any program in memory
the time it takes to find all banks in memory with that same key is too long and would slow down the computer
the number of bits in the key determines the maximum number of jobs that can be in memory at any given point in time

  1. Which key value does the operating system use?
0000
1111
1000
0001

  1. What is one advantage of this key/bank system?
a program's memory space needs to be contiguous in physical memory
a program's memory space does not need to be contiguous in physical memory
the program can pretend to have a lot more memory than really exists
it takes virtually 0 time to compare the keys and check for valid access

  1. When is the logical address compared to the field length register to see if the program has attempted to go outside its memory bounds?
before the logical address is added to the base address
after the logical address is added to the base address
at the same as the logical address is added to the base address

  1. What type of circuit will a computer that uses the base address/field length method of memory protection need?
several more adders
several more multiplexors
more memory