6.5 Review Exercises


Exercise 6.5

  1. The procedure shown below has poor identifiers and no comments. Rewrite the procedure correcting these defects. 
    procedure a (b : real, c : real, d : int)

   const x := 12
   const y := 2
   var e : real
   
   put "Old balance: ", b:x:y
   if b < d then
      put "Balance too low - no interest given"
   else
      e := b * c
      put "Interest given: ", e:x:y
      put "New balance: ", b + e:x:y
   end if
end a

  2. The following procedure uses global variables. Replace these with local variables and parameters.
    %************************************************************
% This procedure prints the tax set at a rate given by      *
% taxRate and the total price of quantity items, each       *
% priced at unitCost.  A flag, taxable, is used to indicate *
% whether or not the items are taxable.                     *
%************************************************************
procedure computeTaxAndPrice
   preTaxPrice := quantity * unitCost
   if taxable then
      tax := preTaxPrice * taxRate
      totalPrice := preTaxPrice + tax
   else
      tax := 0.0
      totalPrice := preTaxPrice
   end if
   put "Tax = $", tax
   put "Total Price = $", totalPrice
end computeTaxAndPrice

  3. Explain the difference between arguments and parameters.

  4. Write and test a procedure that has a single string parameter the contents of which is a single word with, possibly, leading and/or trailing blanks. The procedure is to print only the non-blank characters in the string.

  5. Write a function called countZeroes which will count how many zeroes there are in an array. The procedure will have the following heading: 
    funtion countZeroes(a : array 1 .. * of int) : int

    For example this fragment: 

    var nums: array 1 .. 5 of int := init(0, 1, 2, 0, 3)
var values : array 1 .. 10 of int := init(0, 1, 2, 3, 4, 0, 0, 0, 9, 10)

put "There were ", countZeroes(nums), " zeroes."
put "There were ", countZeroes(values), " zeroes."
    should produce output of:

    There were 2 zeroes.
There were 4 zeroes.

  6. What is the difference in form between a call to a function and a call to a procedure?

  7. Subprograms are to be written for each of the following tasks. State, with reasons, whether a function or a procedure is better suited to each task. Do not write the subprograms.
    1. Examine two integer arrays and produce an array that contains only the elements that appear in both of the other arrays.
    2. Replace all punctuation marks in a string by blanks.
    3. Find the median value in a real array.
    4. Count the number of occurences of the value zero in an integer array.
    5. Print a title page with the purpose of a program and the author's name .

  8. Complete the definition of the function digit with heading
    function digit(number, position : int) : int
    so that the function returns the value of the digit that is position places from the right in number. As examples: 
    digit(8247, 3) = 2
digit(89, 4) = 0

  9. Write a character-valued function convertToGrade that has an integer-valued parameter mark. The function should return the grade that corresponds to mark according to the following table. 
      Mark
--------
 0 - 49
50 - 59
60 - 69
70 - 79
80 - 100
Others
      Grade
  -----
    E
    D
    C
    B
    A
    X

  10. Write a boolean-valued function leapYear with a single int parameter year. The function should return the value true if and only if year is a leap year.