Library Routines

Exam code: 2210

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

Library Routines

What are library routines?

A library routine is reusable code that can be used throughout a program
The code has been made public through reusable modules or functions
Using library routines saves programmers time by using working code that has already been tested
Some examples of pre-existing libraries are:
- Random
- Round

Random

The random library is a library of code which allows users to make use of 'random' in their programs
Examples of random that are most common are:
- Random choices
- Random numbers
Random number generation is a programming concept that involves a computer generating a random number to be used within a program to add an element of unpredictability
Examples of where this concept could be used include:
- Simulating the roll of a dice
- Selecting a random question (from a numbered list)
- National lottery
- Cryptography

Concept	Pseudocode	Python
Random numbers	`RANDOM(1,6)`	`import random` `number = random.randint(1,10)` `number = random.randint(-1.0,10.0)`
Random choice		`import random` `choice = random.choice()`

Concept

Pseudocode

Python

Random numbers

RANDOM(1,6)

import random

number = random.randint(1,10)

number = random.randint(-1.0,10.0)

Random choice

import random

choice = random.choice()

Examples

Random number

Pseudocode	Python
`// (In pseudocode we just use the RANDOM() function, so no import is needed) // Ask user to enter a username and password OUTPUT "Enter a username: " INPUT User OUTPUT "Enter a password: " INPUT Pw // Check if the user and password are correct IF User = "admin" AND Pw = "1234" THEN // Generate a random 4-digit code Code ← ROUND((RANDOM() * 9000) + 1000, 0) // Print the code OUTPUT "Your code is ", Code ELSE OUTPUT "Invalid username or password." ENDIF`	`# importing random library import random # asking user to enter a username and password user = input("Enter a username: ") pw = input("Enter a password: ") # checking if the user and password are correct if user == "admin" and pw == "1234": # generating a random 4-digit code code = random.randint(1000, 9999) # printing the code print("Your code is", code) else: print("Invalid username or password.")`

Pseudocode

Python

// (In pseudocode we just use the RANDOM() function, so no import is needed)

// Ask user to enter a username and password
OUTPUT "Enter a username: "
INPUT User
OUTPUT "Enter a password: "
INPUT Pw

// Check if the user and password are correct
IF User = "admin" AND Pw = "1234" THEN
  // Generate a random 4-digit code
  Code ← ROUND((RANDOM() * 9000) + 1000, 0)
  // Print the code
  OUTPUT "Your code is ", Code
ELSE
  OUTPUT "Invalid username or password."
ENDIF

# importing random library
import random

# asking user to enter a username and password
user = input("Enter a username: ")
pw = input("Enter a password: ")

# checking if the user and password are correct
if user == "admin" and pw == "1234":
    # generating a random 4-digit code
    code = random.randint(1000, 9999)
    
    # printing the code
    print("Your code is", code)
else:
    print("Invalid username or password.")

National lottery

Pseudocode	Python
// Create a list of numbers for the national lottery DECLARE LotteryNumbers : ARRAY[1:49] OF INTEGER FOR Index ← 1 TO 49 LotteryNumbers[Index] ← Index NEXT Index // Create an empty list to store the chosen numbers DECLARE ChosenNumbers : ARRAY[1:6] OF INTEGER // Loop to pick 6 numbers from the list FOR Count ← 1 TO 6 // Use RANDOM to pick a number from the remaining list RandomIndex ← ROUND((RANDOM() * (50 - Count)), 0) IF RandomIndex = 0 THEN RandomIndex ← 1 ENDIF Number ← LotteryNumbers[RandomIndex] // Add the chosen number to the list of chosen numbers ChosenNumbers[Count] ← Number // Remove the chosen number from the list of available numbers FOR i ← RandomIndex TO 48 LotteryNumbers[i] ← LotteryNumbers[i + 1] NEXT i NEXT Count // Sort the chosen numbers in ascending order FOR i ← 1 TO 5 FOR j ← i + 1 TO 6 IF ChosenNumbers[i] > ChosenNumbers[j] THEN Temp ← ChosenNumbers[i] ChosenNumbers[i] ← ChosenNumbers[j] ChosenNumbers[j] ← Temp ENDIF NEXT j NEXT i // Output the chosen numbers OUTPUT "The winning numbers are: " FOR i ← 1 TO 6 OUTPUT ChosenNumbers[i] NEXT i	import random # Create a list of numbers for the national lottery lottery_numbers = list(range(1, 50)) # Create an empty list to store the chosen numbers chosen_numbers = [] # Loop to pick 6 numbers from the list for _ in range(6): # Use random.choice to pick a number from the list number = random.choice(lottery_numbers) # Add the chosen number to the list of chosen numbers chosen_numbers.append(number) # Remove the chosen number from the list of available numbers lottery_numbers.remove(number) # Sort the chosen numbers in ascending order chosen_numbers.sort() # Output the chosen numbers print("The winning numbers are:", chosen_numbers)

Pseudocode

Python

// Create a list of numbers for the national lottery
DECLARE LotteryNumbers : ARRAY[1:49] OF INTEGER
FOR Index ← 1 TO 49
    LotteryNumbers[Index] ← Index
NEXT Index

// Create an empty list to store the chosen numbers
DECLARE ChosenNumbers : ARRAY[1:6] OF INTEGER

// Loop to pick 6 numbers from the list
FOR Count ← 1 TO 6
    // Use RANDOM to pick a number from the remaining list
    RandomIndex ← ROUND((RANDOM() * (50 - Count)), 0)
    IF RandomIndex = 0 THEN
        RandomIndex ← 1
    ENDIF

    Number ← LotteryNumbers[RandomIndex]

    // Add the chosen number to the list of chosen numbers
    ChosenNumbers[Count] ← Number

    // Remove the chosen number from the list of available numbers
    FOR i ← RandomIndex TO 48
        LotteryNumbers[i] ← LotteryNumbers[i + 1]
    NEXT i
NEXT Count

// Sort the chosen numbers in ascending order
FOR i ← 1 TO 5
    FOR j ← i + 1 TO 6
        IF ChosenNumbers[i] > ChosenNumbers[j] THEN
            Temp ← ChosenNumbers[i]
            ChosenNumbers[i] ← ChosenNumbers[j]
            ChosenNumbers[j] ← Temp
        ENDIF
    NEXT j
NEXT i

// Output the chosen numbers
OUTPUT "The winning numbers are: "
FOR i ← 1 TO 6
    OUTPUT ChosenNumbers[i]
NEXT i

import random

# Create a list of numbers for the national lottery
lottery_numbers = list(range(1, 50))

# Create an empty list to store the chosen numbers
chosen_numbers = []

# Loop to pick 6 numbers from the list
for _ in range(6):
    # Use random.choice to pick a number from the list
    number = random.choice(lottery_numbers)

    # Add the chosen number to the list of chosen numbers
    chosen_numbers.append(number)

    # Remove the chosen number from the list of available numbers
    lottery_numbers.remove(number)

# Sort the chosen numbers in ascending order
chosen_numbers.sort()

# Output the chosen numbers
print("The winning numbers are:", chosen_numbers)

Round

The round library is a library of code which allows users to round numerical values to a set amount of decimal places
An example of rounding is using REAL values and rounding to 2 decimal places
The round library can be written as:

ROUND(<identifier>, <places>)

Concept	Pseudocode	Python
Round	`Cost ← 1.9556 OUTPUT ROUND(Cost,2) # Outputs 1.96`	`number = 3.14159 rounded_number = round(number, 2) print(rounded_number) # Outputs 3.14`

Example

// Example using the ROUND function

DECLARE Price : REAL
DECLARE RoundedPrice : REAL

Price ← 12.6789

// Round the value of Price to 2 decimal places
RoundedPrice ← ROUND(Price, 2)

OUTPUT "The rounded price is ", RoundedPrice

So if the variable Price was 12.6789, the output would be:

The rounded price is 12.68

Library Routines

Library Routines

What are library routines?

Random

Examples

Round

Example

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