A-LevelComputer ScienceAlgorithm design and problem-solving9618/22 · May/June 2022 · Q510 Marks

Study the following pseudocode. Line numbers are for reference only. 10 PROCEDURE Encode () 11 DECLARE CountA, CountB, ThisNum : INTEGER 12 DECLARE ThisChar : CHAR 13 DECLARE Flag : BOOLEAN 14 CountA ← 0 15 CountB ← 10 16 Flag ← TRUE 17 INPUT ThisNum 18 WHILE ThisNum <> 0 19 ThisChar ← LEFT(NUM_TO_STR(ThisNum), 1) 20 IF Flag = TRUE THEN 21 CASE OF ThisChar 22 '1' : CountA ← CountA + 1 23 '2' : IF CountB < 10 THEN 24 CountA ← CountA + 1 25 ENDIF 26 '3' : CountB ← CountB – 1 27 '4' : CountB ← CountB – 1 28 Flag ← FALSE 29 OTHERWISE : OUTPUT "Ignored" 30 ENDCASE 31 ELSE 32 IF CountA > 2 THEN 33 Flag ← NOT Flag 34 OUTPUT "Flip" 35 ELSE 36 CountA ← 4 37 ENDIF 38 ENDIF 39 INPUT ThisNum 40 ENDWHILE 41 OUTPUT CountA 42 ENDPROCEDURE

(a)Procedure Encode() contains a loop structure. Identify the type of loop and state the condition that ends the loop. Do not include pseudocode statements in your answer. Type Condition[2]
(b)Complete the trace table below by dry running the procedure Encode() when the following values are input: 12, 24, 57, 43, 56, 22, 31, 32, 47, 99, 0 The first row is already complete. ThisNum ThisChar CountA CountB Flag OUTPUT 0 10 TRUE [6]
(c)Procedure Encode() is part of a modular program. Integration testing is to be carried out on the program. Describe integration testing.[2]

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[2] One mark for type and one mark for condition: Independent marks
Type: pre-condition
Condition: when the value of ThisNum / the input value is equal to zero
[6] Marks as follows: One mark per outlined group If no marks per group then mark by columns (columns 3 to 6) for max 4
ThisNum | ThisChar | CountA | CountB | Flag | OUTPUT
| | 0 | 10 | TRUE |
12 | '1' | 1 | 10 | TRUE |
24 | '2' | 2 | 10 | TRUE |
57 | '5' | 2 | 10 | TRUE | "Ignored"
43 | '4' | 2 | 9 | FALSE| "Ignored"
56 | '5' | 2 | 9 | FALSE|
22 | '2' | 4 | 9 | TRUE | "Flip"
31 | '3' | 4 | 8 | TRUE |
32 | '3' | 4 | 7 | TRUE |
47 | '4' | 4 | 6 | FALSE|
99 | '9' | 4 | 6 | FALSE| "Ignored"
0 | | 4 | 6 | FALSE|
[2] One mark per point:
• Modules that have already been tested individually
• are combined into a single (sub) program which is then tested as a whole

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