Review Exercise 4.5 Solutions

    1. In both cases if you used or instead of and then there would be values that would get you out of the loop.
    1. no value of response will stop the loop (it can't be two different characters at the same time)
    2. no value of response will stop the loop (it can't be less than 'A' and at the same time greater than 'E')

    1. C
 D
  E
   F
    G
     H
    2. 50 51 52 53 54 
40 41 42 43 44 
30 31 32 33 34 
20 21 22 23 24 
10 11 12 13 14
    3. 40 33 26 19 12 5

      1. var count : int := 2
loop
   if count mod 10 = 0 then
      put ""
   end if
   put count, " ", count ** 2
   count := count + 2
   exit when count > 40
end loop 
      2. var power : int
for i : 1 .. 5
   for j : 0 .. 4
      power := 1
      for k : 1 .. j
         power := power * i
      end for
      put "    ", i, "\^", j, "  ", power
  end for
  put ""
end for 
      1. 2 4
4 16
6 36
8 64

10 100
12 144
14 196
16 256
18 324

20 400
22 484
24 576
26 676
28 784

30 900
32 1024
34 1156
36 1296
38 1444

40 1600
      2.     1^0  1
    1^1  1
    1^2  1
    1^3  1
    1^4  1

    2^0  1
    2^1  2
    2^2  4
    2^3  8
    2^4  16

    3^0  1
    3^1  3
    3^2  9
    3^3  27
    3^4  81

    4^0  1
    4^1  4
    4^2  16
    4^3  64
    4^4  256

    5^0  1
    5^1  5
    5^2  25
    5^3  125
    5^4  625

    1. 540 has 3 3's
    2. To find the number of times divisor (3) goes into number. 

  5. const width : int := 5
var divisor, quotient, remainder : int

divisor := 1
for position : 1 .. width -1
   divisor := divisor * 10
end for

get remainder
% added this line
put "$"..
for decreasing position : width .. 1
   quotient := remainder div divisor
   % added the if statement - originally only the statement after the else was there
   if remainder < divisor then
      put "*"..
   else 
      put quotient ..
   end if
   remainder := remainder mod divisor
   divisor := divisor div 10
end for
put "" 

  6. var number : int

put "Enter a natural number"
get number

put number, " has the following exact divisors: 1"..

if number not= 1 then
   put ", "..
   for count : 2 .. number div 2
      if number mod count = 0 then
         put count, ", "..
      end if
   end for
   put number..
end if

put "." 

  7. var numDays, firstDay : int
var current : int := 1

put "How many days in the month?"
get numDays
put "What day is the first day? (1 = Sunday, 2 = Monday, 3 = Tuesday,"
put "4 = Wednesday, 5 = Thursday, 6 = Friday, 7 = Saturday"
get firstDay

put "Sun  Mon  Tue  Wed  Thu  Fri  Sat"
% handle first week
for i : 1 .. 7
   if i < firstDay then
      put "     "..
   else
      put "  ", current, "  "..
      current := current + 1
   end if
end for

% print the rest of the weeks
loop
   put ""
   exit when current > numDays
   for i : 1 .. 7
      % Don't go past the end of the month
      if current <= numDays then
         if current < 10 then
            put "  ", current, "  "..
         else
            put " ", current, "  "..
         end if
         current := current + 1
      end if
   end for
end loop 
  8. % n - the current number to check if it is prime
% factors - counts the number of factors of n (if > 2 then not prime)
% count - the number of primes (we are trying to find the first 5000
var factors, count : int := 0
var n : int := 1

loop
   factors := 0
   n := n + 1

   % find the number of factors for the current n
   for i : 1 .. n
      if n mod i = 0 then
         factors := factors + 1
      end if
   end for

   % if it is prime then print it
   if factors <= 2 then
      put n, " "..
      count := count + 1
      % print them 10 to a line
      if count mod 10 = 0 then
         put ""
      end if
   end if
   exit when count = 500
end loop