Lesson 3.1: Code is Instructions for the Computer

Duration: 45 minutes

Learning Objectives

After completing this lesson, you will be able to:

• Explain what programming is in simple terms
• Understand how computers interpret and execute instructions
• Recognize the difference between human language and programming languages
• Write your first pseudo-code instructions

Introduction

You've been programming your whole life without knowing it. Every time you followed a recipe, gave someone directions, or explained how to play a game, you were essentially programming a human. The only difference with computers is that they need instructions to be extremely precise.

Programming is simply writing instructions that a computer can understand and execute.

Main Content

What is Code?

Code is a set of written instructions. Just like a recipe tells you how to bake a cake step by step, code tells a computer what to do step by step.

Here's a simple comparison:

The key difference? Computers are literal. They do exactly what you tell them, nothing more, nothing less.

The Precision Problem

Imagine telling a robot to make a peanut butter sandwich. You might say:

"Put peanut butter on bread."

A human would understand this perfectly. But a computer might:

• Try to place the entire jar on the bread
• Not know which side of the bread to use
• Not realize it needs to open the jar first
• Not know how much peanut butter to use

To a computer, you'd need to say:

1. Pick up the bread bag
2. Open the bread bag
3. Remove two slices of bread
4. Place both slices on the plate
5. Pick up the peanut butter jar
6. Twist the lid counterclockwise to open
7. Pick up the knife
8. Insert knife into jar
9. Scoop approximately 1 tablespoon of peanut butter
10. Spread peanut butter evenly on one slice
11. Place the other slice on top
12. Done

This level of detail is what programming requires.

How Computers Execute Code

Computers don't understand English, Russian, or any human language. They only understand machine code — sequences of 1s and 0s called binary.

Human writes:    print("Hello")
                      ↓
Translator converts to machine code:
                 01001000 01100101 01101100 01101100 01101111
                      ↓
Computer executes and displays: Hello

The "translator" that converts your code to machine code is called a compiler or interpreter (we'll learn more about these later).

The Building Blocks of Code

All programming, regardless of the language, uses these fundamental concepts:

┌─────────────────────────────────────────────────────────────┐
│                    PROGRAMMING BASICS                        │
├─────────────────────────────────────────────────────────────┤
│                                                              │
│  ┌─────────────┐  Store information                         │
│  │  VARIABLES  │  Example: age = 25                         │
│  └─────────────┘                                            │
│                                                              │
│  ┌─────────────┐  Make decisions                            │
│  │ CONDITIONS  │  Example: if age >= 18 then "adult"        │
│  └─────────────┘                                            │
│                                                              │
│  ┌─────────────┐  Repeat actions                            │
│  │   LOOPS     │  Example: repeat 10 times: print "Hi"      │
│  └─────────────┘                                            │
│                                                              │
│  ┌─────────────┐  Reusable instruction sets                 │
│  │ FUNCTIONS   │  Example: calculateTax(price)              │
│  └─────────────┘                                            │
│                                                              │
└─────────────────────────────────────────────────────────────┘

Pseudo-code: Planning Before Coding

Before writing actual code, programmers often write pseudo-code — instructions written in plain language that describe what the program should do.

Example: ATM Withdrawal

START
    Ask user for PIN
    IF PIN is correct THEN
        Ask for withdrawal amount
        IF amount <= account balance THEN
            Dispense cash
            Update account balance
            Print receipt
        ELSE
            Show "Insufficient funds"
        END IF
    ELSE
        Show "Invalid PIN"
    END IF
END

This isn't real code, but it clearly describes the logic. Once you have this, translating it to any programming language becomes much easier.

From Idea to Execution

Here's the journey from your idea to a running program:

┌──────────┐    ┌──────────────┐    ┌─────────────┐    ┌──────────┐
│  YOUR    │ → │  WRITE CODE  │ → │  TRANSLATE   │ → │ COMPUTER │
│  IDEA    │    │  (Source)    │    │  (Compile)   │    │ EXECUTES │
└──────────┘    └──────────────┘    └─────────────┘    └──────────┘

Example:
"Show greeting"  →  print("Hello!")  →  01001000...  →  Hello!

Why Learn to Code?

Programming gives you superpowers:

Programming isn't about being a "computer person." It's about solving problems efficiently and automating repetitive work.

Practice Exercise

Task 1: Write Pseudo-code

Write pseudo-code for a simple traffic light system. The light should:

• Show green for 30 seconds
• Then yellow for 5 seconds
• Then red for 30 seconds
• Repeat forever

START
    REPEAT FOREVER
        Turn light GREEN
        Wait 30 seconds
        Turn light YELLOW
        Wait 5 seconds
        Turn light RED
        Wait 30 seconds
    END REPEAT
END

Task 2: Spot the Missing Instruction

This pseudo-code for making coffee has a problem. What's missing?

START
    Fill kettle with water
    Boil water
    Put coffee in cup
    Pour water into cup
    Add sugar if desired
    Drink coffee
END

Task 3: Daily Life Algorithm

Think of something you do every day (brushing teeth, making breakfast, getting dressed). Write pseudo-code with at least 8 steps that a robot could follow.

Key Takeaways

• Programming is writing precise instructions for computers to follow
• Computers are literal — they do exactly what you tell them, nothing more
• All code eventually becomes binary (1s and 0s) that computers can execute
• The four building blocks of programming are: variables, conditions, loops, and functions
• Pseudo-code helps you plan your logic before writing actual code
• Programming is about solving problems and automating tasks

Resources