31
4-17. Which of the following statements
describes the method used in computers
to subtract binary numbers?
1. R's complement the minuend and
add to the subtrahend
2. Add the minuend and subtrahend
and complement the sum
3. R's complement the subtrahend and
add to the minuend
4. Subtract the subtrahend from the
minuend and complement the
difference
Figure 4D.—Adder/subtracter circuit.
IN ANSWERING QUESTIONS 4-18
THROUGH 4-20, REFER TO FIGURE 4D.
4-18. What type of complement is performed
by X-OR gates 1 and 2?
1. R's complement
2. Minuend complement
3. R's + 1 complement
4. Difference complement
4-19. Which of the following inputs is used
for the least significant digit of the
minuend?
1. A1
2. A2
3. B1
4. B2
4-20. What will be the output of (a) X-OR 2
and (b) X-OR 1 in the subtract mode
with a subtrahend of 102?
1. (a) 0 (b) 0
2. (a) 0 (b) 1
3. (a) 1 (b) 0
4. (a) 1 (b) 1
4-21. Flip-flops are what type of
multivibrators?
1. Astable
2. Monostable
3. Free running
4. Bistable
4-22. Flip-flops may NOT be used for which
of the following operations?
1. Temporary storage
2. Subtraction
3. Division
4. Transfer of information
4-23. When, if ever, will the outputs Q and Q
of an R-S flip-flop be the same?
1. When R and S are both LOW
2. When R is LOW and S is HIGH
3. When R is HIGH and S is LOW
4. Never
