Algorithm specification test questions - Higher Computing Science Revision

1

This algorithm is designed to validate user input until they enter a value between 0 and 50 inclusive.

Line 1 FOR counter FROM 0 TO 4 DOLine 2 RECEIVE score [counter] FROM (INTEGER) KEYBOARDLine 3 WHILE score [counter] ˂0 AND score [counter] ˃ 50 DOLine 4 SEND (“The score you entered was not valid; please enter a score between 0 and 50”)Line 5 RECEIVE score [counter] FROM (INTEGER) KEYBOARDLine 6 END WHILELine 7 END FOR

Identify the logic error shown in this algorithm.

Line 1 – The counter should run from 1 to 5 rather than 0 to 4

Line 4 should be ≤ and ≥ rather than ˂ and ˃

Line 4 – Should be OR instead of AND

2

This algorithm is designed to perform a linear search.

Line 1 SET item_found TO FALSELine 2 SET counter TO 0Line 3 RECEIVE desired_item FROM (STRING) KEYBOARDLine 4 REPEATLine 5 IF desired_item = nation[counter] THENLine 6 SET item_found TO TRUE Line 7 END IFLine 8 SET counter TO counter + 1Line 9 UNTIL counter = 10 OR item_found = TRUE

The loop used in this example is:

A fixed loop

A pre-test conditional loop

A post-test conditional loop

3

This algorithm is designed to find the maximum value held within an array called testscore which will hold ten values.

Line 1 SET maximum TO testscore [0]Line 2 FOR counter FROM 1 TO 9 DOLine 3 IF testscore[counter] ˃ maximum THENLine 4 SET maximum TO testscore[counter]Line 5 END IFLine 6 END FOR

Explain why the fixed loop is set to run from 1 TO 9

Because indexing starts at 1 in reference language examples

Because the first testscore has already been set as the maximum value

Because 1 TO 9 means ten, 1 added to 9 and there are ten values in the array

4

This algorithm is designed to find the minimum value held within an array called testscore. This array will hold ten values.

Line 1 SET minimum TO testscore [0]Line 2 FOR counter FROM 1 TO 9 DOLine 3 IF testscore[counter] ˃ minimum THENLine 4 SET minimum TO testscore[counter]Line 5 END IFLine 6 END FOR

Explain the role of the variable ‘counter’ in this example.

To store the current value of minimum

To hold a value that will correspond to the array index locations that the loop should iterate over

To count the number of times that the minimum value changes

5

The algorithm shown below has been designed to count the number of times a number is found within an array.

Line 1 SET occurrence TO 0Line 2 RECEIVE desired_value FROM KEYBOARDLine 3 FOR counter FROM 0 TO 9 DOLine 4 IF age [counter] = desired_valueLine 5 Line 6 END IFLine 7 END FOR

Line 5 is missing. Which of the following should be shown on line 5?

SET desired_value TO counter + occurrence

SET counter TO counter + 1

SET occurrence TO occurrence + 1

6

Why is the use of meaningful identifiers important when creating an algorithm?

To ensure that the program is maintainable

So that programmers have a clear idea of how the algorithm is structured prior to creating corresponding code in a high level language

Because white space and indentation make the algorithm easy to follow when a programmer comes to create the corresponding code in a high level language

7

This algorithm should output the final value of occurrence. Line 6 is not in the correct place. Where should line 6 be placed?

Line 1 SET occurrence TO 0Line 2 RECEIVE desired_value FROM KEYBOARDLine 3 FOR counter FROM 0 TO 9 DOLine 4 IF age [counter] = desired_valueLine 5 SET occurrence TO occurrence + 1Line 6 SEND occurrence TO DISPLAYLine 7 END IFLine 8 END FOR

After what is currently line 2

On line 7, with line 7 moving to line 6

After what is currently line 8

8

Select the correct definition for the term algorithm.

A step by step process for solving a problem in Computing Science

An already determined function that requires no further implementation as it is present within a high level language

A formula used in programming to help find the quickest method of solving a problem

9

This algorithm is designed to carry out a linear search. Complete the missing part of line 9 by selecting the correct answer as shown below.

Line 1 SET item_found TO FALSELine 2 SET counter TO 0Line 3 RECEIVE desired_item FROM (STRING) KEYBOARDLine 4 REPEATLine 5 IF desired_item = nation[counter] THENLine 6 SET item_found TO TRUELine 7 END IFLine 8 SET counter TO counter + 1Line 9 UNTIL counter = 10 OR

item_found = FALSE

End of nation list

item_found = TRUE

10

If the user enters the score 71 on line 2, why would this value not be held within the score array by the time the second iteration of the fixed loop takes place?

Line 1 FOR counter FROM 0 TO 4 DOLine 2 RECEIVE score [counter] FROM (INTEGER) KEYBOARDLine 3 WHILE score [counter] ˂0 OR score [counter] ˃ 50 DOLine 4 SEND (“The score you entered was not valid; please enter a score between 0 and 50”)Line 5 RECEIVE score [counter] FROM (INTEGER) KEYBOARDLine 6 END WHILELine 7 END FOR

Because the score is always re-determined on line 5, regardless of what is entered on line 2

Because a conditional loop would be initiated on line 3 if a value like 71 was entered on line 2. The conditional loop would repeat infinitely until a value between 0 and 50 were entered

Because the value entered on line 2 is set as the counter value as demonstrated by the presence of [counter] on line 2