# Control Flow and the if Statement – How Programs Make Decisions >
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I recently started teaching a course on C programming and as part of my preparation for class, I usually write out lesson notes that I will be teaching from. I have therefore decided to make these into blog posts so anyone else learning C can also benefit from them. Therefore, this lesson is part of the series I am calling: C Programming for Absolute Beginners. I hope you enjoy it. Ask any questions or leave comments if you need further clarification or want to make a suggestion.
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In the [previous lesson](https://blog.ehoneahobed.com/variables-in-c-how-programs-store-data), your program could store and print data. Now we move to something more powerful. We will teach the program how to **make decisions**. Because real programs don’t just run from top to bottom. They check conditions and decide what to do next. In this lesson, you’ll learn: * What control flow is * How C evaluates conditions * How to use the `if` statement * How comparison operators work Let’s begin. ## 1\. What Is Control Flow? By default, C runs code from top to bottom. Example: ```c printf("Hello\n"); printf("World\n"); ``` The output will always be: ```plaintext Hello World ``` This is called **sequential execution**. But what if we want something to happen only when a condition is true? That’s where control flow comes in. Control flow determines: * Which code runs * When it runs * Whether it runs at all ## 2\. Understanding Conditions A condition is something that can be either: * True * False Example: ```plaintext 5 > 3 → true 2 == 10 → false ``` In C: * True is any non-zero value * False is zero You don’t need to memorize that deeply yet. Just remember: conditions must evaluate to true or false. ## 3\. The `if` Statement The `if` statement allows a program to run code only if a condition is true. ### Basic Syntax ```c if (condition) { // code runs if condition is true } ``` Notice: * The condition is inside parentheses. * The code block is inside curly braces `{ }`. ## 4\. Simple Example ```c #include int main() { int age = 20; if (age >= 18) { printf("You are an adult.\n"); } return 0; } ``` Explanation: * `age >= 18` is the condition. * If it is true, the message prints. * If it is false, nothing happens. ## 5\. Comparison Operators These operators help us create conditions.

Operator

Meaning

==

equal to

!=

not equal

>

greater than

<

less than

>=

greater than or equal

<=

less than or equal

Example: ```c if (score == 50) ``` Important Warning: `=` means assignment `==` means comparison Beginners mix this up all the time. This is wrong: ```c if (score = 50) ``` This assigns 50 instead of checking it. Always use `==` when comparing. ## 6\. Another Example: Pass or Not ```c #include int main() { int score = 45; if (score >= 50) { printf("You passed!\n"); } return 0; } ``` Here: * If score is 50 or more → it prints. * If score is below 50 → nothing prints. The program makes a decision. ## 7\. What Happens If the Condition Is False? If the condition is false, the code inside the braces does not run. Example: ```c int temperature = 10; if (temperature > 30) { printf("It is hot.\n"); } ``` Since 10 is not greater than 30, nothing prints. The program simply moves on. ## 8\. Common Beginner Mistakes 1. Using `=` instead of `==` 2. Forgetting parentheses around the condition 3. Forgetting curly braces 4. Writing conditions that don’t make sense (like `if (5)`) Always structure it like this: ```c if (condition) { // action } ``` ## 9\. Practice Exercises Try writing these programs: 1. Create a variable called `number`. If it is greater than 0, print “Positive”. 2. Create a variable called `age`. If it is 18 or more, print “Can vote”. 3. Create a variable called `temperature`. If it is less than 15, print “Cold”. ## Final Thoughts Today you learned how to: * Understand program flow * Write conditions * Use comparison operators * Control when code runs This is the beginning of real logic in programming. In the next lesson, we will expand this with: * `if–else` * `else if` * Logical operators like AND and OR And that’s when your program starts thinking in more complex ways.