Question

The problem is that I am not sure how to load the data from keyboard to a two dimentional array when column number is unknown. Specifically, I need a program to store students’ grades for 4 subjects whithout knowing the actual number of students.

I have come up with this (I am fairly certain that the decision is faulty, but it’s the best I’ve got so far):

Declare Grades as dynamic two dimentional array of int
 Loop: Subject = 1 to 4
 Print 'Enter students grades for subject' + Subject#
 Print 'Enter * when done'
 If Grades <=100 && Grades >=0 then
  While Grades <> '*'
   Enter Grades w/o cursor return
  WhileEnd
  Else
   Print 'Enter a valid grade'
 EndIf
 LoopEnd: Subject

I guess that it’s not clear from this code how the Subject loop functions, i.e. when it goes from subject1 to subject2 and so on. I initially thought that to achieve the goal I would simply need to return cursor (which would have been done after a user entered ‘*’), but it’s hardly true, is it?

So could you please-please help me understand this problem better?

Thank you.

Answer 1

A couple of things are wrong with your pseudocode:

1. You’re trying to validate grade before you have read it
2. You’re not explicitly populating the 2-dimensional array Grades
3. You’re not dealing with the student index into the array

If you’ll like to iterate over the subjects and then the students, you could do it this way:

Declare Grades as dynamic two dimensional array of int
 Loop: Subject = 1 to 4
   Print 'Enter students grades for subject' + Subject#
   Print 'Enter * when done'
   initialize student = 1
   Repeat 
     Read Grades[student, subject] from the keyboard
     If Grades[student, subject] <=100 && Grades[student, subject] >=0 then
       student = student + 1
     Else
      Print 'Enter a valid grade for ' + student + ' in subject ' + subject
     EndIf
   Until Grades = '*'
 LoopEnd: Subject