04 Try it yourself Interactive

Build the trace table one cell at a time

Same loop and same number as section 02, 4729, with one extra column for the condition test. Each press of Next executes exactly one statement and writes exactly one cell. Three things move together: the cell being filled, the line of code that fills it, and the sentence explaining it. Switch to Reverse to see that the loop skeleton — the condition on line 2, the digit on line 3, the step on line 5 — never changes; only the accumulator does, renamed on lines 1 and 6 and given a different update rule on line 4. Then load 0 and watch the body run zero times.

Sum of digits
sum = sum + digit
One whole number, 0 to 999999.
Press Next to begin. Each press executes one statement and writes one cell.


      

        
Pass–

        
n–

        
digit–

        
accumulator (sum)0

      


      

      

        
        
        
        step 0 / 0