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 A variable (integer) can be used to count values that satisfy a certain condition. 
Remember counting always
starts from 0 so the value of the variable must be initialised to 0. 
Example 
20 marks are to be input.
How many of them are over 50? 
We will use a variable
called 'counter' to store the number of marks over
50. 
The pseudocode algorithm is.. 
    
        counter  = 0 
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        | for
        20 times do | 
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        input (mark) | 
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        if
        the  mark is over 50 then | 
        
     
    
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        add 1 to  counter | 
     
    
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        end if | 
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        | end do | 
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        | output
        (counter) | 
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