Ask students to calculate 17 + 28. Easy. Now ask them to add 15 to the result. Still easy. Now ask them to multiply THAT by 3. Getting harder to track. This is why computers need variables - to remember things. Demo a simple program: what happens if we try to greet someone without storing their name first?

Introduce variables as labelled boxes that hold data. Cover: creating variables, assigning values, reassigning. Use physical boxes with labels as props. Show the difference between variable (box can be emptied and refilled) and constant (sealed box - value fixed forever). Live code examples: storing a name, storing a score, storing a high score that shouldn't change (constant).

How do we get data INTO a variable? Input! How do we see what's in it? Output! Live code a simple greeting program that asks for a name and says hello. Then extend: ask for age, calculate birth year, display it. Emphasise that code runs line by line (sequence).

In pairs, students create a 'personal assistant' that: asks for their name, asks for their favourite colour, asks for their lucky number, then outputs a personalised message using all three. Extension: make the lucky number a constant and try to change it - what happens?

Brief story of Mars Climate Orbiter. Show how unclear variable usage (mixing units) caused a spacecraft to crash. Discuss: why might professional programmers care so much about variable naming?

Quiz game: show scenarios (e.g., 'player's current score', 'the value of pi', 'number of lives remaining', 'maximum level in the game'). Students vote: variable or constant? Discuss reasoning. Exit ticket: define variable, constant, input, output in your own words.

Live demo: In Python, show that 5 + 3 = 8. Then show that "5" + "3" = "53". Ask: what on earth is going on? Let students discuss. Reveal: the quotes change EVERYTHING. Computers treat numbers-as-text differently from actual numbers.

Systematically introduce each type with relatable examples. Integer: age, score, lives remaining. Real/float: price, temperature, percentage. Boolean: logged_in, game_over, is_adult. Character: grade ('A'), initial ('J'). String: name, address, tweet. Use a sorting activity: students categorise real-world data into types (e.g., 'phone number' - trick question! It's a string because you don't do maths with it).

Sometimes we need to change types. Demo: asking user for age (input gives string), then trying to add 1 to it (error!). Solution: casting with int(). Show int(), float(), str(), bool() conversions. Discuss: when might we need to cast? (User input, calculations, displaying numbers in sentences).

Students complete a worksheet identifying correct data types for scenarios, then write short programs that: (1) Calculate the cost of items with decimal prices, (2) Ask if the user is a member (Boolean) and give appropriate discount, (3) Take a birth year as input and calculate age. Must use appropriate types and casting.

Quick story of Y2K and how a simple data type decision (2-digit years) nearly caused global chaos. Show authentic news footage from 1999. Ask: what data type decisions do YOU make that might matter in 20 years?

Show code snippets with deliberate type errors. Students must spot the error and suggest the fix. Exit ticket: What data type would you use to store (1) a password, (2) the number of items in a shopping basket, (3) whether sound is muted?

Ask the class: what is 17 ÷ 5? Accept answers (3.4, 3, 3 remainder 2). Reveal: in programming, ALL these answers are correct - it depends which operator you use! This lesson is about understanding WHEN to use each.

Quick review of addition, subtraction, multiplication, and division. Emphasise that / in most languages gives a decimal result. Live code a simple calculator. Introduce operator precedence (BIDMAS/BODMAS applies in programming too!).

Deep dive into the three operators students often haven't seen. DIV: integer division (17 DIV 5 = 3, throws away remainder). MOD: modulo/remainder (17 MOD 5 = 2). ^: power (2^3 = 8). Use visual examples: sharing sweets (DIV = sweets each, MOD = leftovers). Physical activity: students distribute counters and record DIV and MOD results.

Scenario matching activity. Students match problems to operators: calculating change from purchase (+, -), working out if a year is a leap year (MOD), calculating compound interest (^), converting hours to days and remaining hours (DIV, MOD), splitting a bill (/).

Create a program that: takes a price and amount paid, calculates change, breaks change into pounds and pence (hint: DIV and MOD!). Extension: calculate minimum coins needed for the change (harder!).

Brief mention that MOD is the foundation of encryption that secures online banking, WhatsApp messages, and more. The maths behind keeping your data safe uses modular arithmetic constantly.

Students predict outputs of expressions without running code. Include precedence challenges like 3 + 4 * 2 (11, not 14) and MOD/DIV problems. Self-mark and discuss any surprises. Exit ticket: write an expression that would help split 100 tasks among 7 workers (how many each, how many spare).

Show a YouTube age-restriction screen. Ask: how does YouTube make this decision? Students discuss in pairs. It's selection - an IF statement! 'IF age >= 18 THEN show video ELSE show restriction'. Every app they use is constantly making decisions.

Before we can make decisions, we need to ask questions. Introduce all comparison operators with examples. Key emphasis: == is asking 'are these equal?' while = is assignment. This is a crucial distinction! Live code showing the difference between if x = 5 (error in many languages) and if x == 5.

Build up from simple to complex. First: IF only (do something or don't). Then: IF-ELSE (do one thing or another). Then: IF-ELIF-ELSE (multiple pathways). Use a grade boundary example: IF score >= 70 'A', ELIF score >= 60 'B', etc. Trace through with different values.

Sometimes we need to check something, THEN check something else. Example: Cinema pricing - check if child, then check if it's a weekday. Nested IFs. Emphasise indentation - how we (and the computer) keep track of which decisions belong together.

In small groups, design and code the logic for a theme park ride that checks: minimum height (120cm), maximum height (200cm), and whether they have a health condition that prevents riding. Must use appropriate selection structures. Groups present their logic to another group who 'tests' it with different inputs.

Brief discussion: What happens when the decisions computers make affect people's lives? Loan applications, job screening, medical diagnosis. Who's responsible when an algorithm makes a wrong decision? Introduce the idea that code has ethical implications.

Show code with deliberate selection errors (wrong operator, missing ELSE, incorrect nesting). Students identify and fix the bugs. Exit ticket: Write selection logic for 'Can this person vote?' (must be 18+ and a citizen).

Challenge: Write code to print 'Hello' 1000 times. A student might start typing print statements... after about 10, ask 'How long would this take?' Reveal: with a loop, it's just 2-3 lines. Computers are built to repeat things - that's their superpower.

Introduce the FOR loop structure. Analogy: it's like saying 'Do this 10 times' rather than 'Do this. Do this. Do this...' Cover: loop variable, start value, end value. Live code examples: printing numbers 1-10, printing a name 5 times, counting down from 10 to 1.

Sometimes we don't want to count by 1. Introduce step values: counting by 2 (even numbers), counting by 5 (times tables), counting backwards (step -1). Live code: print all even numbers up to 20, countdown from 10 for a rocket launch.

The loop variable isn't just for counting - we can use it! Examples: print '2 x 1 = 2, 2 x 2 = 4, ...' (times tables). Calculate the sum of numbers 1-100. Draw patterns where position depends on iteration number.

In pairs, students create programs for: (1) Print the 7 times table up to 7x12, (2) Print all numbers from 100 to 0, going down in tens, (3) Calculate and print the total of 1+2+3+...+50. Extension: print a simple triangle pattern made of stars (* then ** then *** etc.).

Quick peek at how games use loops. Show a simplified game loop structure: 'forever: get input, update world, draw frame'. Every game students play is essentially one giant loop running 60+ times per second.

Students complete trace tables for FOR loops, predicting output and the value of variables at each iteration. Include one with a common error (off-by-one). Exit ticket: How many times will this loop run? What will it output?

Play a quick number guessing game with the class. After a few rounds, ask: 'How would I code this? I can't use FOR 10 times - what if someone guesses correctly on attempt 2? Or attempt 50?' We need a loop that keeps going UNTIL something happens.

Introduce WHILE: check a condition BEFORE each iteration. 'While the password is wrong, ask again.' Key point: if the condition is already false, the loop might run ZERO times! Live code a password checker that keeps asking until correct.

Sometimes we need to do something AT LEAST ONCE before checking. DO UNTIL: execute first, then check condition. 'Do ask for input UNTIL input is valid.' Live code a menu system that must show at least once before checking if user wants to exit.

Present scenarios; students decide which loop type to use. 'Repeat exactly 5 times' → FOR. 'Keep asking until valid input' → WHILE or DO UNTIL. 'Show menu, then ask if they want to continue' → DO UNTIL. Discuss why each answer is correct.

Students code a number guessing game: computer picks a number 1-100, player guesses, program says 'too high' or 'too low' and asks again UNTIL they guess correctly. Count the attempts. Extension: add a maximum of 10 guesses (combine WHILE with a counter).

Deliberately create an infinite loop (while True). Discuss: why is this dangerous? How do we avoid it? Key insight: every WHILE/DO UNTIL must have a way to eventually become false. Show how to stop a runaway program.

Quick-fire matching: given a problem, students hold up cards for FOR/WHILE/DO UNTIL. Discuss any disagreements. Exit ticket: Write a WHILE loop that keeps asking for a positive number until the user enters one.

Present a scenario: A secure door opens IF you have a valid badge AND (you're an employee OR a verified visitor) AND NOT currently locked down. How would we code this? One IF statement can't handle it alone. We need to COMBINE conditions.

Introduce AND operator. For the whole expression to be True, BOTH sides must be True. Examples: 'If age >= 17 AND has_licence == True: can drive'. 'If temperature > 100 AND patient_conscious == False: call ambulance'. Create truth table together.

Introduce OR operator. For the whole expression to be True, AT LEAST ONE side must be True (including both). Examples: 'If day == "Saturday" OR day == "Sunday": weekend'. 'If payment_method == "cash" OR payment_method == "card": accept payment'.

Introduce NOT operator. Flips True to False and vice versa. Examples: 'If NOT game_over: continue'. 'If NOT is_banned: allow access'. Often more readable than checking for False directly.

Show how to combine: 'If (age >= 18 OR has_parental_consent) AND NOT is_banned: allow access'. Discuss order of operations (NOT first, then AND, then OR) and how brackets can make intent clearer. Live code the secure door example from the hook.

Extend the theme park ride checker: Person can ride IF (height >= 120 AND height <= 200) AND (NOT has_heart_condition OR has_medical_waiver) AND (age >= 12 OR accompanied_by_adult). Students code this and test with various inputs.

Quick story of George Boole inventing Boolean algebra in 1854, and how Claude Shannon connected it to electronic circuits in 1937. Every AND/OR/NOT in your code connects to actual physical gates in the processor.

Students evaluate Boolean expressions given variable values. Include complex expressions with multiple operators. Exit ticket: Write a Boolean expression for 'User can post IF they're logged in AND (they're the author OR they're an admin) AND the post is NOT deleted'.

Show a website's password requirements: must be 8+ characters, contain uppercase, contain lowercase, contain a number. Ask: how does the website CHECK these things? It's all string manipulation - checking length, checking individual characters, searching for patterns.

Start with the simplest operation: joining strings together. Show 'Hello' + ' ' + 'World'. Build a greeting: 'Hello, ' + name + '!'. Discuss when to use concatenation vs multiple print statements. Show building dynamic messages and file paths.

Every string knows its length. Every character has a position (index). Introduce len() and accessing characters by index. KEY POINT: indexing starts at 0! 'Hello'[0] is 'H'. Live code accessing first character, last character.

Slicing extracts part of a string. string[start:end] gives characters from start up to but not including end. Examples: getting first 4 characters, getting last 3 characters, getting middle section. Show left() and right() equivalents if available in chosen language.

Introduce upper(), lower(), and other useful methods. Show how to check if a string is all uppercase/lowercase. Demonstrate ASC() and CHR() for converting between characters and ASCII codes. These are tools for password validation, text processing, and more.

Create two validators: (1) Username must be 3-15 characters. (2) Password must be 8+ characters AND contain at least one uppercase letter (check each character in a loop). Extension: check for at least one digit too.

Brief look at how string manipulation scales up to NLP. ChatGPT processes millions of words by breaking them into 'tokens' (pieces) and analyzing patterns. What you're learning is the foundation of AI language models.

Given a string and a goal, students work out the operations needed. 'Turn "hello world" into "WORLD"' (slice, then upper). Exit ticket: Write code to extract the domain from an email address.

Challenge: Store the names of everyone in this class. With variables: name1, name2, name3... How many variables? How do you loop through them? How do you add someone new? This quickly becomes unmanageable. Arrays are the solution.

Introduce arrays as a single variable that holds multiple values, each at a numbered position (index). Create arrays with values. Access individual elements by index. Emphasise: arrays are fixed length (static) - set the size when created.

Change individual elements: array[2] = 'new value'. Discuss: you CAN change values, but not easily add/remove in traditional arrays (this is where lists differ). Show common operations: find and replace, update scores, etc.

THIS is where arrays shine. Loop through entire array without knowing values in advance. Examples: print all names, sum all scores, find highest score, count how many items match a condition. The loop variable becomes the index!

Create a program that: stores 5 quiz scores in an array, calculates and displays the total, calculates and displays the average, finds and displays the highest score. Extension: let user enter the scores instead of hard-coding them.

Quick teaser: With a million items, how do you find one quickly? Checking each (linear search) could take a million steps. But if the array is sorted, binary search can find it in about 20 steps! Preview of the algorithms unit.

Given an array and a task, students write the code. Tasks include: print third element, change last element, sum all elements, find position of a value. Exit ticket: Why are arrays better than many separate variables?

Show a spreadsheet of student data: names, ages, quiz scores for 3 quizzes. Ask: how would you store this in code? One array for names, another for ages, another for scores? What if you need to add a column? A 2D array keeps it all together.

Introduce 2D arrays as arrays of arrays - rows containing columns. Declare: array grid[3,4] for 3 rows, 4 columns. Access: grid[row,column]. Trace through examples: what's at grid[1,2]? Mental model: first number picks the row, second picks the column.

To process every element, we need a loop inside a loop. Outer loop for rows, inner loop for columns. Live code: print an entire grid, calculate sum of all values, find the maximum value in the grid.

2D arrays use numbers for columns. But 'student[0,2]' isn't very clear. Records use NAMES for fields: student.name, student.age, student.score. Introduce record structure: defining fields and accessing them. More readable than array indices!

Create a game leaderboard system. Use either a 2D array or an array of records (group chooses) to store: player name, score, level reached. Implement: display all entries, find highest score, find a player by name. Discuss: which approach felt cleaner?

Quick look at how this connects to databases. Every table in a database is conceptually a 2D array of records. What you're learning is the foundation of how websites store user data, products, orders, and everything else.

Given scenarios, students decide: 1D array, 2D array, or record? 'Store temperature readings for 7 days', 'Store student name, ID, and grades', 'Store a chess board'. Discuss reasoning. Exit ticket: Write code to access the score of the second player in a leaderboard.

Show code where the same 10-line block appears 5 times. Ask: What if there's a bug? You fix it 5 times. What if you want to change it? 5 changes. What if you need it in a different program? Copy again. There must be a better way!

Introduce procedures as named blocks of code you can call. Define once, call many times. Show procedure with no parameters, then add parameters to make it flexible. Example: greet() → greet(name) → greet(name, greeting).

Functions compute and RETURN a value. The return value can be stored, printed, or used in calculations. Example: square(5) returns 25. calculateArea(width, height) returns width * height. Key difference: procedure = does something, function = calculates something.

Variables inside functions are LOCAL - they only exist inside that function. GLOBAL variables exist throughout the program. Show the problem: local variable can't be accessed outside. Show the benefit: local variables don't interfere with each other. Demonstrate passing values in and getting values out.

You can pass arrays to functions and return arrays from functions. Example: function that takes an array of scores and returns the highest. Example: function that takes an array and returns a new array with all values doubled.

Create a set of functions: add(a, b), subtract(a, b), multiply(a, b), divide(a, b), average(array), maximum(array). Then create a main program that uses these functions to solve problems. Extension: add error handling (e.g., divide by zero).

Quick tour of how functions power the modern web. When you ask Siri a question, your phone calls functions on Apple's servers. When a game saves your progress to the cloud, it calls functions on remote computers. Functions aren't just local.

Quick fire: given a description, is it a procedure or function? 'Prints a message' (procedure). 'Calculates average' (function). 'Draws a shape' (procedure). 'Checks if password valid' (function - returns Boolean). Exit ticket: Write a function that takes two numbers and returns the larger one.

Demo a high score program. Enter a great score. Close and reopen. Score is gone! Why? Variables only exist while the program runs. To remember anything permanently, we need to SAVE it to a file. Files survive after the program closes.

Files must be opened before use. Show: open(), readLine(), endOfFile check. Loop through file reading each line. Emphasise: always check for end of file! Demo reading a file of names and displaying them. Show what happens if file doesn't exist.

Writing creates or overwrites files. Show writeLine() adding text. Demonstrate: creating a new file, writing multiple lines. Key warning: write mode DESTROYS existing content! Show creating a file vs opening an existing one.

newFile() creates a file before opening. ALWAYS close files when done - close() saves changes and frees the file. Show what can go wrong if you don't close: data corruption, locked files. Introduce with/context managers if applicable to language.

Create a program that: on startup, reads high scores from a file (if it exists). Lets user enter new scores. Saves all scores back to the file before closing. BONUS: keep the file sorted by score (highest first).

Quick peek at real game save files. Show a save file from Minecraft or another game (if possible, a text-readable one). Discuss: what data needs saving? Position, inventory, progress, settings. The same principles, just more data.

Students put file operations in correct order: open, read/write, close. Discuss what goes wrong if steps are missing or out of order. Exit ticket: Write code to read all lines from a file called 'scores.txt' and print each one.

Challenge: I have a database of 1 million books. Find all books by J.K. Rowling published after 2000 that cost less than £15. In a spreadsheet, this is slow and painful. In SQL, it's one line of code, executed in milliseconds. Let's learn how.

Quick intro: databases contain tables. Tables have rows (records) and columns (fields). Show a sample table: Students(StudentID, Name, Age, Year, House). Relate to 2D arrays and records from previous lessons - similar concept, different tool.

The basic query: SELECT columns FROM table. Live demo: SELECT * FROM Students (get everything). SELECT Name, Age FROM Students (get specific columns). Discuss why you might not want ALL columns (efficiency, relevance).

Add conditions: SELECT * FROM Students WHERE Age > 14. Show comparison operators in SQL (=, <, >, <=, >=, <> for not equal). Combine with AND/OR: WHERE Age > 14 AND House = 'Gryffindor'. Build increasingly complex queries.

Given a Products table (ProductID, Name, Category, Price, Stock), students write SQL queries for: all products under £20, all electronics, products with low stock (< 10) in the Food category, all products NOT in Electronics. Groups swap and test each other's queries.

Brief look at SQL in action. Show a simple web form that queries a database behind the scenes. Mention that SQL skills are in high demand: data analysts, web developers, database administrators. Briefly mention SQL injection as a security concern.

Given plain English requests, students write SQL queries. 'Find all customers in London' → SELECT * FROM Customers WHERE City = 'London'. Mix of simple and complex requirements. Exit ticket: What three keywords must every SQL query include?

Imagine a game where enemies always appear in the same place, loot is always the same, dice always roll 6. Boring! Games NEED unpredictability. But computers follow exact instructions... how do they do random?

Introduce the random() function. Random integer in range: random(1, 6) for a dice. Random real number: random(0.0, 1.0). Show multiple calls produce different results. Discuss: what if we want the same 'random' sequence every time? (Seeds - optional advanced topic).

Practical applications: dice simulator, random selection from array (use random to pick an index), coin flip (random(1,2) then check value). Live code: a magic 8-ball that randomly selects from an array of responses.

Put it all together! Create a complete number guessing game: generate random number 1-100, loop until guessed, give hints (too high/low), count attempts, offer play again, keep high score across games (maybe to file!). This combines: random, loops, selection, variables, possibly file handling.

Brief look at randomness beyond games. Lottery numbers, scientific simulations, cryptographic keys. Mention the concept of 'true' randomness vs computer pseudo-randomness. Link to random.org which uses atmospheric noise for true random numbers.

Reflect on the entire unit: What was most challenging? What was most interesting? What would you like to explore further? Share mini-project progress and creative additions. Preview: how these skills connect to broader programming and future topics.