Fundamental Programming Concepts (OCR GCSE Computer Science)

Revision Note

Taking an algorithm and turning it into code, in any language, requires an understanding of several basic programming concepts such as:

Variables
Constants
Assignment
Operators
Inputs
Outputs

Variables, Constants & Assignments

What is a variable?

A variable is a named memory location that holds data that during the execution of a program, the data can change
Variables can store a variety of different types of data such as numbers, text or true/false values
To store data in a variable, the process of assignment is used

What is a constant?

A constant is fixed data that during the execution of a program cannot change
A constant can store a variety of different types of data, similar to variables
Pi is an example of a mathematical fixed value that would typically be stored as a constant

What is assignment?

Assignment is the process of storing data in a variable or constant under a descriptive name
Assignment is performed using the '=' symbol

Assigning variables & constants

Concept	OCR exam reference	Python
Variables	`x = 3` `name = "Save My Exams"`	`x = 3` `name = "Save My Exams"`
Constants	`const vat = 0.2` `const pi = 3.142`	`VAT = 0.2` `PI = 3.142`

Concept

OCR exam reference

Python

Variables

x = 3

name = "Save My Exams"

x = 3

name = "Save My Exams"

Constants

const vat = 0.2

const pi = 3.142

VAT = 0.2

PI = 3.142

Operators, Inputs & Outputs

What is an operator?

An operator is a symbol used to instruct a computer to perform a specific operation on one or more values
Examples of common operators include:
- Arithmetic
- Comparison
- Boolean (AND, OR and NOT)

Arithmetic

Operator	OCR exam reference	Python
Addition	`+`	`+`
Subtraction	`-`	`-`
Multiplication	`*`	`*`
Division	`/`	`/`
Modulus (remainder after division)	`MOD`	`%`
Quotient (whole number division)	`DIV`	`//`
Exponentiation (to the power of)	`^`	`**`

Comparison

Operator	OCR exam reference	Python
Equal to	`==`	`==`
Not equal to	`!=`	`!=`
Less than	`<`	`<`
Less than or equal to	`<=`	`<=`
Greater than	`>`	`>`
Greater than or equal to	`>=`	`>=`

Examples

Operator	OCR exam reference	Python
Addition	`sum = 2 + 2 # 4`	`sum = 2 + 2 # 4`
Multiplication	`sum = 3 * 4 # 12`	`sum = 3 * 4 # 12`
Modulus	`sum = 10 MOD 3 # 1`	`sum = 10 % 3 # 1`
Quotient	`sum = 10 DIV 3 # 3`	`sum = 10 // 3 # 3`
Exponentiation	`sum = 2 ^ 2 # 4`	`sum = 2 ** 2 # 4`
Equal to	`if 3 == 3 then # True`	`if 3 == 3: # True`
Not equal to	`if 5 != 6 then # True`	`if 5 != 6: # True`
Greater than or equal to	`if 10 >= 2 then # True`	`if 10 >= 2: # True`
AND	`number = 10` `if number > 0 and < 20 then` `# True`	`number = 10` `if number > 0 and number < 20:` `# True`

What is an input?

An input is a value that is read from an input device and then processed by a computer program
Typical input devices include:
- Keyboards - Typing text
- Mice - Selecting item, clicking buttons
- Sensors - Reading data from sensors such as temperature, pressure or motion
- Microphone - Capturing audio, speech recognition
Without inputs, programs are not useful as they can't interact with the outside world and always produce the same result

What is an output?

An output is a value sent to an output device from a computer program
Typical output devices include:
- Monitor - Displaying text, images or graphics
- Speaker - Playing audio
- Printer - Creating physical copies of documents or images

Area of a rectangle program

OCR exam reference
`# Get the length and width from the user` `length = input("Enter the length of the rectangle: ")` `width = input("Enter the width of the rectangle: ")` `# Calculate the area` `area = length * width` `# Check if the area is greater than 100` `if area > 100 then` `# Print the results` `print("The area of the rectangle is", area)` `endif`
Python
`# Get the length and width from the user` `length = int(input("Enter the length of the rectangle: "))` `width = int(input("Enter the width of the rectangle: "))` `# Calculate the area` `area = length * width` `# Check if the area is greater than 100` `if area > 100:` `# Print the results` `print("The area of the rectangle is", area)`

OCR exam reference

# Get the length and width from the user

length = input("Enter the length of the rectangle: ")
width = input("Enter the width of the rectangle: ")

# Calculate the area
area = length * width

# Check if the area is greater than 100
if area > 100 then

# Print the results
print("The area of the rectangle is", area)

endif

Python

# Get the length and width from the user

length = int(input("Enter the length of the rectangle: "))
width = int(input("Enter the width of the rectangle: "))

# Calculate the area
area = length * width

# Check if the area is greater than 100
if area > 100:

# Print the results
print("The area of the rectangle is", area)

Worked Example

A cinema calculates ticket prices based on age category

Adult = £13.00
Child = £7.50

The program asks the user to enter their age and calculates the cost of their ticket

A simple algorithm is used

adult = 13.00

child = 7.50

age = input("What is your age: ")

if age > 18 then

total_cost = adult

else

toal_cost = child

end if

print(total_cost)

The cinema decides to add a discount of 25% to customers who come to the cinema on 'Sunday evening'

Identify all the additional inputs that will be required for this change to the algorithm [2]

How to answer this question

What new information is needed?

Answer

day
time

Last updated: 29 July 2024

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