Lesson 1: Introduction to Software Development & Algorithms

A pizza ordering app seems complex, but we can break it into smaller parts:

• Choose pizza size
• Select toppings
• Add to cart
• Enter delivery address
• Process payment
• Track delivery

Each of these is a smaller, manageable problem that's easier to solve!

Whether you're logging into Instagram, Gmail, or Netflix, the pattern is always similar:

• Enter username/email
• Enter password
• Click login button
• Check if credentials are correct
• Either grant access or show error

Once you solve it once, you can reuse this pattern!

Algorithm for making instant coffee:

1. Boil water in kettle
2. Put coffee powder in cup
3. Add sugar (if desired)
4. Pour hot water into cup
5. Stir well
6. Add milk (if desired)
7. Stir again

This is an algorithm! Clear, step-by-step, and anyone can follow it.

START
    Wake up
    Get out of bed
    Brush teeth
    Get dressed
    Eat breakfast
    Pack bag
    Leave house
END

Notice: Order matters! You wouldn't eat breakfast before getting out of bed, right?

# A simple program that greets a user
print("Welcome to my program!")
name = input("What is your name? ")
print("Hello, " + name + "!")
print("Nice to meet you.")

Explanation:

• Line 2: Display a welcome message
• Line 3: Ask for the user's name and store it
• Line 4: Print a personalized greeting
• Line 5: Print a final message

Each line runs in order, one after another.

# Check if someone can vote
age = int(input("How old are you? "))

if age >= 18:
    print("You can vote!")
else:
    print("You're too young to vote.")
    years_until = 18 - age
    print("You can vote in " + str(years_until) + " years.")

Explanation:

• The program asks for age
• if age >= 18: checks if age is 18 or more
• If TRUE: prints "You can vote!"
• If FALSE: runs the else block instead

START
    WHILE there are dirty dishes DO
        Pick up one dish
        Wash the dish
        Dry the dish
        Put it away
    END WHILE
    Clean the sink
END

The actions inside the WHILE loop repeat until all dishes are clean.

# Print numbers from 1 to 5
for number in range(1, 6):
    print("Count: " + str(number))

print("Done counting!")

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5
Done counting!

Explanation:

• for number in range(1, 6): creates a loop
• The loop runs 5 times (1, 2, 3, 4, 5)
• Each time, it prints the current number
• After the loop finishes, it prints "Done counting!"

START
    Generate random number between 1 and 10
    Store it as 'secret_number'

    Display "Guess a number between 1 and 10"
    Get user's guess

    IF guess equals secret_number THEN
        Display "Correct! You won!"
    ELSE IF guess is less than secret_number THEN
        Display "Too low! Try again."
    ELSE
        Display "Too high! Try again."
    END IF
END

Notice how we use:

• Sequence: Steps happen in order
• Selection: IF/ELSE to make decisions

import random

# Generate secret number
secret_number = random.randint(1, 10)

# Get user's guess
print("Guess a number between 1 and 10:")
guess = int(input())

# Check if correct
if guess == secret_number:
    print("Correct! You won!")
elif guess < secret_number:
    print("Too low! Try again.")
else:
    print("Too high! Try again.")

Line-by-line explanation:

• Line 1: Import the random module (gives us random numbers)
• Line 4: Generate a random number from 1-10
• Line 7-8: Ask user for input and convert to integer
• Line 11-16: Check the guess and give feedback

import random

# Generate secret number
secret_number = random.randint(1, 10)
guesses = 0

print("I'm thinking of a number between 1 and 10.")
print("Can you guess it?")

# Keep looping until they get it right
while True:
    guess = int(input("Your guess: "))
    guesses = guesses + 1

    if guess == secret_number:
        print("Correct! You won!")
        print("It took you " + str(guesses) + " guesses.")
        break  # Exit the loop
    elif guess < secret_number:
        print("Too low! Try again.")
    else:
        print("Too high! Try again.")

New concepts:

• while True: Creates a loop that runs forever (until we break out)
• guesses = guesses + 1: Counts how many attempts
• break: Exits the loop when they guess correctly

• Use input() to get user input
• Use int() or float() to convert strings to numbers
• Use if/elif/else to check which operation to perform
• Remember: + adds, - subtracts, * multiplies, / divides