6.2: Reading Algorithms

What is an algorithm?

An algorithm is a set of instructions, presented in a logical sequence.

In an exam you may be asked to read and understand an algorithm that has been written. To prove your understanding you may be asked to respond by actions such as listing the outputs of the algorithm or identifying an error within it.

Example Algorithm:

Start NewProgram

 

number is integer

maxvalue is integer

input maxvalue

for i = 1 to maxvalue

     output (i * i)

???????

output 'program finished'

End NewProgram

Example Questions:

1. List the outputs produced by the algorithm if the 'maxvalue' input is 5.

2. State the code that has been replaced by '???????' and what the code's purpose is.

Example Answers:

1.

Outputs:

1

4

9

16

25

program finished

2.

Missing Code: next i

Purpose: Moves the loop to the next iteration.

Previous Exam Questions to try

2014 Exam Algorithm:

set counter = 0

output "Before the loop"

repeat

       set counter = counter + 1

      output "Count is" counter

until counter = 3

output "Loop has ended"

2015 Exam Algorithm:

Total is integer

Mean is real

i is integer

startmainprog

    set Total = 0

  

    for i = 1 to 5

          set Total = Total + i

         output "Total is", Total

     next i 

     set Mean = Total / 5

     output "Mean is", Mean

endmainprog

2014 Exam Question:

Write down all the outputs produced by the algorithm.

2016 Exam Algorithm 1:

M is integer

P is integer

i is integer

startmainprog

    input M

    for i = 1 to 4

         set P = i * M

         output P

     endfor

endmainprog

2015 Exam Question:

2016 Exam Question 1:

Write down all the outputs produced by the algorithm when the value of M input is 3.

Write down all the outputs in the correct order produced by the algorithm.

2016 Exam Algorithm 2:

Total is ? {stores the total of the numbers input}

Mean is ? {stores the mean of the numbers input}

Count is ? {stores the loop control value}

startmainprog

     set Total = 0 {initialise variables}

     set Count = 0

     repeat

          set Count = Count + 1

          set Total = Total + Count

     until Count = 20

     output "The total is ", Total

     set Mean = Total / 20

     output "mean is ", Mean

endmainprog

2017 Exam Algorithm 1:

HighNum is integer 

Total is integer

i is integer

startmainprog

     input HighNum

     set Total = 0

     if HighNum < 1 then

          output "Number not valid"

     else

          for i = 1 to HighNum

               set Total = Total + i

               output Total

          endfor

     endif

endmainprog

2016 Exam Question 2:

State, giving a reason for each, the most suitable data type for the variables below:

     a. Mean

     b. Count

2017 Exam Question 1:

Write down all the outputs in the correct order produced by the algorithm for the input below:

     a. Input is 0

     b. Input is 4

2017 Exam Algorithm 2:

IF (X > 5) AND (Y < 7) THEN

OUTPUT true

ELSE

OUTPUT false

ENDIF

2017 Exam Question 2:

Write down the output for the following values of X and Y:

      a. X = 2 and Y = 4

      b. X = 5 and Y = 4

      c. X = 6 and Y = 6

2019 Exam Algorithm:

Start addProc

number is integer

a is integer

total is integer

if i = 1 to 5

     output "Please enter next number"

     input number

     a = a + number

next i

total = a

output "The total = ", total

End addProc

2019 Exam Question:

1. Identify the error in this algorithm and suggest a suitable change to this code to address the error.

2. Suggest a suitable change to address the inefficient use of memory in this algorithm.

6.2 - Reading Algorithms:

Answer each of the previous exam questions on this page.

Exam Board:

Eduqas / WJEC

Specification:

2016 + 

Questo's Questions

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