Pearson Edexcel IGCSE · Computer Science
2 multiple-choice questions marked as you go, and 4 written questions with worked solutions. All on Constructs.
Study the following pseudocode which involves variable scope:
\( \text{SET globalVar TO 10} \)
\( \text{FUNCTION calculate(n)} \)
\( \text{SET localVar TO n * 2} \)
\( \text{SET globalVar TO globalVar + 5} \)
\( \text{RETURN localVar} \)
\( \text{ENDFUNCTION} \)
If the main program calls \( \text{calculate(4)} \) once, what will be the final value of globalVar and the returned result?
Consider the following pseudocode fragment:
\( \text{SET count TO 0} \)
\( \text{FOR r FROM 0 TO 2} \)
\( \text{FOR c FROM 0 TO 1} \)
\( \text{IF vals[r][c] > 10 THEN} \)
\( \text{SET count TO count + 1} \)
\( \text{END IF} \)
\( \text{END FOR} \)
\( \text{END FOR} \)
The 2D array \( \text{vals} \) contains the following data:
Row 0: 12, 5
Row 1: 8, 15
Row 2: 20, 7
What will be the final value of the variable \( \text{count} \) after execution?
Explain the primary difference between a count-controlled iteration and a condition-controlled iteration.
Write your answer out first, then check it against the worked solution.
An algorithm uses a nested loop to calculate the sum of values in a 2D array. If the inner loop is defined as \( \text{FOR j FROM 0 TO 5} \) but the array rows only contain 4 elements (indices 0 to 3), identify the type of error that occurs and explain its impact on the program execution.
Write your answer out first, then check it against the worked solution.
Selection and iteration are fundamental programming constructs.
(a) Describe the difference between a count-controlled loop (FOR loop) and a condition-controlled loop (WHILE loop).
(b) Provide one specific programming scenario where a WHILE loop would be a more appropriate choice than a FOR loop.
Write your answer out first, then check it against the worked solution.
A programmer is writing a subprogram to calculate the discount on a customer order.
(a) Explain the difference between passing by value and passing by reference when providing arguments to a subprogram.
(b) Discuss the benefits of using local variables within this subprogram instead of using global variables to track calculation steps, referring to data security and memory management.
Write your answer out first, then check it against the worked solution.
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