Program Flow in C

Theory

Controlling program flow is essential in any language. C provides control structures (if, else, switch), loops (for, while, do-while), and functions to organize and direct execution.

Control Structures

The if/else statement executes code based on a condition. C uses relational operators (==, !=, <, >, <=, >=) and logical operators (&&, ||, !). The switch statement efficiently selects among multiple discrete values.

if (score >= 90) {
    printf("Grade: A");
} else if (score >= 80) {
    printf("Grade: B");
} else {
    printf("Grade: C");
}

Loops

• for — iterate a known number of times: for(int i = 0; i < 10; i++)
• while — repeat while a condition is true: while(count > 0)
• do-while — execute body at least once: do { ... } while(condition)

Functions

Functions in C have a return type, a name, parameters, and a body. They enable code reuse, modularity, and abstraction. Function declarations (prototypes) inform the compiler about a function before its definition.

Why this matters

Control flow and functions are the core of every C program. Whether you're writing a simple calculator or an embedded system driver, mastering conditionals, loops, and function design is essential for writing correct, maintainable C code.

What's next

In the next lessons, you'll dive deeper into each topic with hands-on examples and exercises.

Practical Examples

Exercises

#include <stdio.h>\n\nint main() {\n  int sum = 0;\n  // Your code here\n  return 0;\n}

2550

Mini Quiz