Grade Calculator Solution
Author: Jordan Kidney ( kidney@cpsc.ucalgary.ca )   Date: Feb 14, 2006
When looking at the task of creating this program there are 4 main components that can be extracted:
  1. Reading in information from the user
    • The students grade on the test (Mark)
    • The total number of marks that a student could get on the test (TotalMarks)
    • This will also require error checking on the numbers entered by the user. The total marks should be greater then zero. The mark by the student must be greater then or equal to zero and less then the total number of marks on the test.
  2. Making some Calculations
    • Calculating the percentage the student got ( Percentage = (Mark * 100)/TotalMarks )
  3. Comparing the percentage value against the table to get a letter grade
    • This will require the use of if and if else statements
  4. Output of information to the user.


Here is a link to the file with the solution in it: GradeCalculator.p

Code

Extra Info

 

(* ==============================================================================
 *    File: GradeCalculator.p
 *  Purpose: Simple program to calculate the percentage and letter grade
 *  Author: Jordan Kidney ( kidney@cpsc.ucalgary.ca )
 * Created on: Feb 14, 2006
  ============================================================================== *)
program GradeCalculator (input,output);

(* ========================== MAIN ============================================== *)
begin
      var Mark        : real; (* The mark the user got *)
      var TotalMarks  : real; (* Total number of possible marks *)
      var Percentage  : real; (* Used to store the calculated percentage value *)
      var LetterGrade : char; (* Used to store the letter cade for the mark *)
      var LetterSign  : char; (* Used to store the sign for the letter grade *)
      var EndLoop     : boolean; (* Used as a flag to end loops for error checking *)

      (* Read in the total marks for the test and make sure
       * it is greaterr then zero                                 *)

      EndLoop := false;
      repeat
          write('Enter the total number of marks : ');
          readln(TotalMarks);
      if (TotalMarks <= 0) then
               writeln('Error: The number must be greater then zero.')
      else
         EndLoop := true

      until EndLoop = true;

      (* Read in the mark the user got and make sure
       * that it is grwater ten or equal to zero and les then the
       *  total number of marks for the test                      *)

       EndLoop := false;
       repeat
          write('Enter your mark : ');
          readln(Mark);
          if ((Mark < 0) or (Mark > TotalMarks))  then
         writeln('Error: inncorect input')
      else
         EndLoop := true

       until EndLoop = true;

      (* Calculate the percentage value for the user *)
      Percentage := (Mark * 100.0)/TotalMarks;

      (* Find the letter grade based upon the percentage value found *)
      if (Percentage < 39.0) then
     begin
        LetterGrade := 'F'; LetterSign  := ' ';
     end
      else if (Percentage < 44.0) then
         begin
           LetterGrade := 'D'; LetterSign  := '-';
     end
      else if (Percentage < 49.0) then
     begin
        LetterGrade := 'D'; LetterSign  := ' ';
     end
      else if (Percentage < 54.0) then
     begin
        LetterGrade := 'D'; LetterSign  := '+';
     end
      else if (Percentage < 59.0) then
     begin
        LetterGrade := 'C'; LetterSign  := '-';
     end
      else if (Percentage < 64.0) then
     begin
        LetterGrade := 'C'; LetterSign  := ' ';
     end
      else if (Percentage < 69.0) then
     begin
        LetterGrade := 'C'; LetterSign  := '+';
     end
      else if (Percentage < 74.0) then
     begin
        LetterGrade := 'B'; LetterSign  := '-';
     end
      else if (Percentage < 79.0) then
     begin
        LetterGrade := 'B'; LetterSign  := ' ';
     end
      else if (Percentage < 84.0) then
     begin
        LetterGrade := 'B'; LetterSign  := '+';
     end
      else if (Percentage < 89.0) then
     begin
        LetterGrade := 'A'; LetterSign  := '-';
     end
      else
     begin
        LetterGrade := 'A'; LetterSign  := ' ';
     end;

      (* Write information to the console *)
      writeln('You got ',
               Percentage:0:2,
          '% on the test which gives you a letter grade of '
          ,LetterGrade,LetterSign);
end.
(* ============================================================================== *)








Variable declaration: Mark, TotalMarks, Percentage are all declared as real (floating point) to keep the type consistent for the calculation of the percentaged. Because the division of the mark and total mark could result in decimal places it is a good idea to declare then as real.



Read in information: For error checking each case for reading in information from the user is encased in a repeat - until loop. This will force the user to enter the proper values before the program continues. In the case of TotalMarks we have to make sure the number is greater then zero. For logical sense the total marks could not be negative. Also we want to make sure the TotalMarks is not zero to prevent a runtime error when we calculate the percentage.














Basic Calculation: find the percentage the user got on the test



Find a letter grade: Find the letter grade based upon the results from the calculation made above. This is done by comparing the value using an if else ladder.
































Output information: To keep everything at one point all the information is outputted to the user at the end of the program instead of at incremental points. This allows for quick and easy changes in one location, if required.