Designing, Creating & Refining Algorithms (OCR GCSE Computer Science)

A hotel car park charges £4 per hour. If the car is electric, this price is halved to £2 per hour.

Write an algorithm to:

• take as input the number of hours the user has parked and whether their car is electric or not

• calculate and output the total price

• repeat continually until the user enters 0 hours.

You must use either:

• OCR Exam Reference Language, or

• a high level programming language that you have studied.

A program needs to perform the following tasks:

• Input two numbers from the user

• Compare both numbers and output the largest number.

Complete the pseudocode for this program.

num1 = ……………………………………………… 

num2 = input("enter second number") 

……………………… num1 > ……………………… then

     ……………………………………………… 

else

     ……………………………………………… 

endif

A second program needs to perform the following tasks:

• Input a number from the user

• Double the number input and print the result

• Repeat bullets 1 and 2 until the user enters a number less than 0.

Write an algorithm for this program.

The following program uses a condition-controlled loop.

x = 15

y = 0

while x > 0

      y = y + 1

      x = x – y

endwhile

print(y)

Complete the trace table to test this program.

Ali’s computer uses virtual memory. Ali has written two procedures to help himself understand how virtual memory works.

storeData() describes how data is stored in RAM.
accessData() describes how data is read from RAM

Write the letter of the missing statements from the table in the correct place to complete the algorithms.

Not all statements are used, and some statements might be used more than once.

procedure storeData()

    if RAM is ......................... then

        move data from RAM to ...............................

    endif

    store data in next free space in ......................... 

....................................................

procedure accessData()

    if .................... (data required is in RAM) then

        if RAM is full then

            move unneeded data from RAM to HDD

        endif

        move required data from HD to RAM

    endif

    read data from ...................

endprocedure

Dru writes the following program using a high-level language.

01 function newscore(a,b) 
02     temp = a*b 
03     temp = temp + 1 
04     return temp 
05 endfunction 
06 score = 18 
07 name = "Dru" 
08 print (score) 
09 print ("name") 
10 print (newscore(score,2)) 
11 print (score)

The following table contains the program code for each line where this program outputs values.

State the values output by the program on each of the lines.

A vending machine can be in one of three states: on, off or suspended. A user can change the state of the vending machine by using the following algorithm.

newstate = input("Enter the new state : ") 

switch newstate: 

        case "on": 

                     statevalue = 1 

         case "off": 

                     statevalue = 2 

         case "suspended": 

                     statevalue = 3 

         default: print("Invalid state") 

endswitch

Rewrite the algorithm to perform the same actions using IF statements in place of the switch statement.

A programmer has written an algorithm to output a series of numbers. The algorithm is shown below:

01 for k = 1 to 3 

02     for p = 1 to 5 

03         print (k + p) 

04     next p 

05 next k 

06 m = 7 

07 print m * m

Give the first three numbers that will be printed by this algorithm

State how many times line 03 will be executed if the algorithm runs through once.

A fast food restaurant offers half-price meals if the customer is a student or has a discount card.

The offer is not valid on Saturdays.

A computer system is used to identify whether the customer can have a half-price meal.

The table identifies the three inputs to the computer system:

The restaurant needs an algorithm designing to help employees work out if a customer can have a half price meal or not. It should:

• input required data

• decide if the customer is entitled to a discount

• output the result of the calculation.

Design the algorithm using a flowchart.

Each member of staff that works in a restaurant is given a Staff ID. This is calculated using the following algorithm.

01     surname = input("Enter surname") 

02     year = input("Enter starting year") 

03     staffID = surname + str(year) 

04     while staffID.length < 10 

05         staffID = staffID + "x" 

06     endwhile 

07     print("ID " + staffID)

Complete the following trace table for the given algorithm when the surname “Kofi” and the year 2021 are entered.

You may not need to use all rows in the table.

Jack is writing a program to add up some numbers. His first attempt at the program is shown.

a = input("Enter a number")

b = input("Enter a number")

c = input("Enter a number")

d = input("Enter a number")

e = input("Enter a number")

f = (a + b + c + d + e)

print(f)

Jack decides to improve his program. He wants to be able to input how many numbers to add together each time the algorithm runs, and also wants it to calculate and display the average of these numbers.

Write an algorithm to:

• ask the user to input the quantity of numbers they want to enter and read this value as input

• repeatedly take a number as input, until the quantity of numbers the user input has been entered

• calculate and output the total of these numbers

• calculate and output the average of these numbers.

When a new booking is recorded, the details are entered into a program to validate the values. The following criteria are checked:

• firstName and surname are not empty

• room is either “basic” or “premium”

• nights is between 1 and 5 (inclusive).

If any invalid data is found “NOT ALLOWED” is displayed. If all data is valid “ALLOWED” is displayed.

Complete the following program to validate the inputs.

firstName = input("Enter a first name")

surname = input("Enter a surname")

room = input("Enter basic or premium")

nights = input("Enter between 1 and 5 nights")

stayComplete = False

You must use either:

• OCR Exam Reference Language, or

• a high-level programming language that you have studied.

A program creates usernames for a school. The first design of the program is shown in the flowchart in Fig. 2.

Fig. 2

The program design is updated to create usernames as follows:

• If the person is a teacher, their username is the last 3 letters of their surname and then the first 2 letters of their first name.

• If the person is a student, their username is the first 3 letters of their first name and then the first 2 letters of their surname.

What would be the username for a teacher called Fred Biscuit using the updated process?

Write an algorithm for the updated program design shown in part(a).

Data for one week (Monday to Friday) is stored in a 2D array with the identifier minsPlayed.

The following table shows part of this array, containing 4 students.

The teacher writes a program to add up and print out the total number of minutes student 2 played computer games over 5 days (Monday to Friday).

total = 0

total = total + minsPlayed[2,0]

total = total + minsPlayed[2,1]

total = total + minsPlayed[2,2]

total = total + minsPlayed[2,3]

total = total + minsPlayed[2,4]

print(total)

Refine the program to be more efficient. Write the refined version of the algorithm.

You must use either:

• OCR Exam Reference Language, or

• a high-level programming language that you have studied.

The following flowchart outputs a message depending on how long each person has spent playing computer games.

Rewrite the flowchart as a program.

You must use either:

• OCR Exam Reference Language, or

• a high-level programming language that you have studied.

Taylor is writing an algorithm to record the results of an experiment.

Taylor needs to be able to enter a numeric value which is added to a total which initially starts at 0.

Every time she enters a value, the total is output.

The algorithm repeats until the total is over 100.

Write an algorithm to implement Taylor’s requirements.

For the next part of the experiment, Taylor needs to be able to enter 10 values and count how many of the values are over 50, outputting this value once all values have been entered.

Complete the following flowchart to implement this algorithm

Write a pseudocode algorithm that uses iteration to allow Taylor to:

• enter 10 values

• count how many values are over 50

• output the count of values over 50 after all 10 values are entered.

OCRBlocks is a game played on a 5 × 5 grid. Players take it in turns to place blocks on the board. The board is stored as a two-dimensional (2D) array with the identifier gamegrid

Fig. 6.1 shows that players A and B have placed three blocks each so far

Write an algorithm to allow player A to select a position for their next block on the game board.

The algorithm must:

• ask the player for the position of their block on the board

• use the checkblock() function to check if this position is free

• if the position is free, add the letter "A" to the position chosen in the gamegrid array

• if the position is not free, repeat the above steps until a free position is chosen.

The algorithm for one section a the vending machine program is shown in pseudocode

if money >= price then
    venditem()
    giveChange(money – price)
else
    print("Error – not enough money inserted")
endif

Draw the vending machine algorithm as a flowchart.

The following names of students are stored in an array with the identifier studentnames.

studentnames = ["Rob", "Anna", "Huw", "Emma", "Patrice", "Iqbal"]

A school uses the array to call an attendance register every morning.

Write an algorithm using iteration to:

• display the name of each student one at a time from studentnames

• take as input whether that student is present or absent

• display the total number of present students and number of absent students in a suitable message, after all student names have been displayed.

One encryption method is a Caesar cipher.

This Caesar cipher moves each letter of the alphabet one place to the right.

The following table shows the original letters in the first row, and the new letters in the second row.

For example, if the message read: HELLO

This would be stored as: IFMMP

The following pseudocode algorithm takes a string of uppercase letters as input and uses the Caesar cipher to encrypt them.

The functions used in the algorithm are described in the table:

Complete the pseudocode algorithm to perform a Caesar cipher.

01 message = input("Please enter your string") 

02 newMessage = "" 

03 messageLength = message.length 

04 for count = 0 to............................ 

05     ASCIIValue = ASC(message.subString(...............,1)) 

06     ASCIIValue = ASCIIValue + .......... 

07     if ASCIIValue >90 then 

08         ASCIIValue = ................................ – 26 

09     endif 

10     newMessage = .................... + CHR(ASCIIValue) 

11 next count

The algorithm needs adapting. An extra line (line 12) is needed to output the encrypted message.

Write line 12 to output the encrypted message in pseudocode or programming code.

Write this algorithm using pseudocode.

A single record from this database table is read into a program that uses an array with the identifier studentdata. An example of this array is shown below:

studentdata = [“Kirstie”, “Homework forgotten”, “-2”, “FALSE”]

The array is zero based, so studentdata[0] holds the value “Kirstie”.

Write an algorithm that will identify whether the data in the studentdata array shows that a letter has been sent home or not for the student. The algorithm should then output either “sent” (if a letter has been sent) or “not sent” (if a letter has not been sent).

Using pseudocode, write an algorithm that will use a count-controlled loop to print out the numbers 1 to 10 in ascending order.

OCR town are holding an election with three candidates (A, B and C). An electronic voting booth will be used to allow people to vote.

Write an algorithm that:

• Allows voters to enter either A, B or C.

• Keeps track of how many times each candidate has been voted for.

• As soon as one person has finished voting, allows the next person to vote.

• At any point allows the official to type in “END”, which will print out the number of votes for each candidate and the total number of votes overall.