Procedures & Functions

Exam code: 2210

Written by: Ashika|Reviewed by: Caroline Carroll|Updated 2 July 2026

What are functions and procedures?

Functions and procedures are a type of sub program, a sequence of instructions that perform a specific task or set of tasks
Procedures and functions are defined at the start of the code
Sub programs are often used to simplify a program by breaking it into smaller, more manageable parts
Sub programs can be used to:
- Avoid duplicating code and can be reused throughout a program
- Improve the readability and maintainability of code
- Perform calculations, to retrieve data, or to make decisions based on input
Parameters are values that are passed into a sub program
- Parameters can be variables or values and they are located in brackets after the name of the sub program
- Example: FUNCTION TaxCalculator(pay,taxcode) OR PROCEDURE TaxCalculator(pay,taxcode)
Sub programs can have multiple parameters
To use a sub program you 'call' it from the main program

What's the difference between a function and procedure?

A Function returns a value whereas a procedure does not

Procedures

Procedures are defined using the PROCEDURE keyword in pseudocode or def keyword in Python
A procedure can be written as:

PROCEDURE <identifier>
<statements>
ENDPROCEDURE
Or if parameters are being used:

PROCEDURE <identifier>(<param1>:<data type>, <param2>:<data type>...)
<statements>
ENDPROCEDURE

Creating a procedure
Pseudocode
`PROCEDURE calculate_area(length: INTEGER, width: INTEGER) area ← length * width OUTPUT "The area is ",area END PROCEDURE`
Python
`def ageCheck(age): if age > 18: print("You are old enough") else: print("You are too young")`

To call a procedure, it can be written as:

CALL <identifier>
CALL <identifier>(Value1,Value2...)

Calling a procedure
Pseudocode
`CALL Calculate_area CALL Calculate_area(5,3)`
Python
`ageCheck(21) print(ageCheck(21))`

Examples

A Python program using procedures to display a menu and navigate between them
Procedures are defined at the start of the program and the main program calls the first procedure to start
In this example, no parameters are needed

Procedures
# Procedure definition for the main menu def main_menu(): # Outputs the options print("1. Addition") print("2. Subtraction") print("3. Multiplication") print("4. Division") print("5. Exit") # Asks the user to enter their choice choice = int(input("Enter your choice: ")) if choice == 1: addition() elif choice == 2: subtraction() elif choice == 3: multiplication() elif choice == 4: division() elif choice == 5: exit_program() # Procedure definition for addition def addition(): num1 = int(input("Enter the first number: ")) num2 = int(input("Enter the second number: ")) print("Result:", num1 + num2) # Procedure definition for subtraction def subtraction(): num1 = int(input("Enter the first number: ")) num2 = int(input("Enter the second number: ")) print("Result:", num1 - num2) # Procedure definition for multiplication def multiplication(): num1 = int(input("Enter the first number: ")) num2 = int(input("Enter the second number: ")) print("Result:", num1 * num2) # Procedure definition for division def division(): num1 = int(input("Enter the first number: ")) num2 = int(input("Enter the second number: ")) if num2 != 0: print("Result:", num1 / num2) else: print("Error: Division by zero is not allowed.") # Procedure to exit the program def exit_program(): print("Exiting the program. Goodbye!") exit() # Main program while True: # Loop to continuously show the menu until the user chooses to exit main_menu()

Procedures

# Procedure definition for the main menu
def main_menu():
    # Outputs the options
    print("1. Addition") 
    print("2. Subtraction")
    print("3. Multiplication")
    print("4. Division")
    print("5. Exit")

    # Asks the user to enter their choice
    choice = int(input("Enter your choice: ")) 
    if choice == 1: 
        addition() 
    elif choice == 2:
        subtraction()
    elif choice == 3:
        multiplication()
    elif choice == 4:
        division()
    elif choice == 5:
        exit_program()

# Procedure definition for addition
def addition(): 
    num1 = int(input("Enter the first number: "))
    num2 = int(input("Enter the second number: ")) 
    print("Result:", num1 + num2) 

# Procedure definition for subtraction
def subtraction():
    num1 = int(input("Enter the first number: "))
    num2 = int(input("Enter the second number: "))
    print("Result:", num1 - num2)

# Procedure definition for multiplication
def multiplication():
    num1 = int(input("Enter the first number: "))
    num2 = int(input("Enter the second number: "))
    print("Result:", num1 * num2)

# Procedure definition for division
def division():
    num1 = int(input("Enter the first number: "))
    num2 = int(input("Enter the second number: "))
    if num2 != 0:
        print("Result:", num1 / num2)
    else:
        print("Error: Division by zero is not allowed.")

# Procedure to exit the program
def exit_program():
    print("Exiting the program. Goodbye!")
    exit()

# Main program
while True:  # Loop to continuously show the menu until the user chooses to exit
    main_menu()

Functions

Functions are defined using the FUNCTION keyword in pseudocode or def keyword in Python
Functions always return a value so they do not use the CALL function, instead they are called within an expression
A function can be written as:

FUNCTION <identifier> RETURNS <data type>
<statements>
ENDFUNCTION
Or if parameters are being used:

FUNCTION <identifier>(<param1>:<data type>, <param2>:<data type>...) RETURNS <data type>
<statements>
ENDFUNCTION

Creating and using a function
Pseudocode
`FUNCTION calculate_area(length: INTEGER, width: INTEGER) area ← length * width RETURN area ENDFUNCTION # Output the value returned from the function OUTPUT(calculate_area(5,3))`
Python
`def squared(number): squared = number^2 return squared # Output the value returned from the function print(squared(4))`

Examples

A Python program using a function to calculate area and return the result
Two options for main program are shown, one which outputs the result (# 1) and one which stores the result so that it can be used at a later time (# 2)

Functions
# Function definition, length and width are parameters def area(length, width): area = length * width # Calculate area return area # Return area # Main program #1 length = int(input("Enter the length: ")) width = int(input("Enter the width: ")) print(area(length, width)) # Calls the area function and prints the result # Main program #2 length = int(input("Enter the length: ")) # Input for length width = int(input("Enter the width: ")) # Input for width calculated_area = area(length, width) # Stores the result of the function in a variable print("The area is " + str(calculated_area) + " cm^2") # Outputs the result with a message

Functions

# Function definition, length and width are parameters
def area(length, width): 
    area = length * width  # Calculate area
    return area  # Return area

# Main program #1
length = int(input("Enter the length: ")) 
width = int(input("Enter the width: ")) 
print(area(length, width))  # Calls the area function and prints the result

# Main program #2
length = int(input("Enter the length: "))  # Input for length
width = int(input("Enter the width: "))  # Input for width
calculated_area = area(length, width)  # Stores the result of the function in a variable
print("The area is " + str(calculated_area) + " cm^2")  # Outputs the result with a message

Worked example

An economy-class airline ticket costs £199. A first-class airline ticket costs £595.

(A) Create a function, flightCost(), that takes the number of passengers and the type of ticket as parameters, calculates and returns the price to pay.

You do not have to validate these parameters

You must use :

a high-level programming language that you have studied [4]

(B) Write program code, that uses flightCost(), to output the price of 3 passengers flying economy.

You must use :

a high-level programming language that you have studied [3]

How do I answer this question?

(A)

Define the function, what parameters are needed? where do they go?
How do you calculate the price?
Return the result

(B)

How do you call a function?
What parameters does the function need to return the result?

Answers

Part

Python

def flightCost(passengers, type):
  if type == "economy":
    cost = 199 * passengers
  elif type == "first":
    cost = 595 * passengers
  return cost

print(flightCost("economy", 3)

x = flightCost("economy", 3)

print(x)

What are functions and procedures?

What's the difference between a function and procedure?

Procedures

Procedures

Examples

Functions

Functions

Examples

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