Chapter 8

True/False

1. False
   
2. True
3. False
4. True
5. False
6. False
7. True
8. True
9. False
10. True
    

Multiple Choice

1. a
   
2. c
3. d
4. c
5. c
6. c
7. d
8. b
9. c
10. a
    

Discussion

1.  
   1. When a definite loop begins executing, the number of iterations is known.
   2. A for loop generally implements a definite loop, and a while is used to implement an indefinite loop.
   3. Both are techniques for getting an indefinite amount of input. The interactive loop asks the user if there is more data, while a sentinel loop continues until a special value is encountered.
   4. An end-of-file loop is a special kind of sentinel loop where the end of input is "signaled" by coming to the end of a file.
2.  
   

   1. P	Q	P and Q	not (P and Q)
      False	False	False	True
      False	True	False	True
      True	False	False	True
      True	True	True	False

   2. P	Q	not P	(not P) and Q
      False	False	True	False
      False	True	True	True
      True	False	False	False
      True	True	False	False

   3. P	Q	not P	not Q	(not P) or (not Q)
      False	False	True	True	True
      False	True	True	False	True
      True	False	False	True	True
      True	True	False	False	False

   4. P	Q	R	P and Q	(P and Q) or R
      False	False	False	False	False
      False	False	True	False	True
      False	True	False	False	False
      False	True	True	False	True
      True	False	False	False	False
      True	False	True	False	True
      True	True	False	True	True
      True	True	True	True	True

   5. P	Q	R	P or R	Q or R	(P or R) and (Q or R)
      False	False	False	False	False	False
      False	False	True	True	True	True
      False	True	False	False	True	False
      False	True	True	True	True	True
      True	False	False	True	False	False
      True	False	True	True	True	True
      True	True	False	True	True	True
      True	True	True	True	True	True

3. While loop fragments: 

1. sum = 0
   i = 1
   while i <= n:
       sum = sum + i
       i = i + 1

2. sum = 0
   i = 1
   while i < 2*n:
       sum = sum + i
       i = i + 2

3. sum = 0
   x = input("Enter a number: ")
   while x != 999:
       sum = sum + x
       x = input("Enter a number: ")

4. count = 0
   while n > 1:
       n = n / 2
       count = count + 1
   

Programming Exercises