Identifying Errors (Cambridge (CIE) IGCSE Computer Science): Exam Questions

An algorithm has been written in pseudocode to allow some numbers to be input. All the positive numbers that are input are totalled and this total is output at the end. An input of 0 stops the algorithm.

01 Exit ← 1 
02 WHILE Exit <> 0 DO 
03      INPUT Number 
04      IF Number < 0 
05        THEN 
06         Total ← Total + Number 
07        ELSE 
08         IF Number = 0 
09           THEN 
10            Exit ← 1 
11         ENDIF 
12       ENDIF 
13 ENDIF 
14 OUTPUT "The total value of your numbers is ", Number

Identify the four errors in the pseudocode and suggest a correction for each error.

An algorithm has been written in pseudocode to calculate a check digit for a four-digit number. The algorithm then outputs the five-digit number including the check digit. The algorithm stops when –1 is input as the fourth digit.

01 Flag FALSE 
02 REPEAT 
03     Total 0 
04     FOR Counter 1 TO 4 
05        OUTPUT "Enter a digit ", Counter 
06        INPUT Number[Counter] 
07        Total Total + Number * Counter 
08        IF Number[Counter] = 0 
09          THEN 
10            Flag TRUE 
11        ENDIF 
12      NEXT Counter 
13      IF NOT Flag 
14        THEN 
15          Number[5] MOD(Total, 10) 
16          FOR Counter 0 TO 5 
17            OUTPUT Number[Counter] 
18          NEXT 
19       ENDIF 
20 UNTIL Flag

Identify the three errors in the pseudocode and suggest a correction for each error.

An algorithm has been written in pseudocode to input some numbers. It only outputs any numbers that are greater than or equal to 100. The number 999 is not output and stops the algorithm.

INPUT Number
WHILE Numbers <> 999 DO
   IF Number > 100
      THEN
         OUTPUT Number
   ENDIF
ENDWHILE
OUTPUT Number

Identify the four errors in the pseudocode and suggest corrections.

Write a pseudocode statement to change the corrected algorithm to output all numbers between 100 and 200 inclusive.

You do not need to rewrite the whole algorithm

This section of program code asks for 80 numbers between 100 and 1000 inclusive to be entered. The pseudocode checks that the numbers are in the correct range and then stores the valid numbers in an array. It counts how many of the numbers are larger than 500 and then outputs the result when finished.

01 Count ← 0 
02 FOR Index ← 1 TO 80 
03     INPUT "Enter a number between 100 and 1000 ", Number 
04         WHILE Number <= 99 AND Number >= 1001 
05         INPUT "This is incorrect, please try again", Number 
06     ENDWHILE 
07     Num[80] ← Number 
08     IF Number > 500 THEN Count ← Count + 1 ENDIF 
09 UNTIL Index = 80 
10 PRINT Index 
11 PRINT "numbers were larger than 500"

There are four lines of code that contain errors.

State the line number for each error and write the correct code for that line.