Functions in C Programming

Study Notes

Functions in C Programming

A function is a block of code that performs a specific task.
Every C program must have at least one function, the main() function.
Functions can call other functions, and themselves (recursion).
Functions improve code reusability and readability.
Functions allow large programs to be broken into smaller modules.
Functions can be called any number of times.

Types of Functions

Standard Library Functions: Built-in functions provided by the C library.
- Examples: printf(), scanf(), pow(), sqrt(), etc.
- Declared in header files (e.g., stdio.h, math.h).
User-Defined Functions: Functions created by the programmer.

Function Components

Function Declaration (Prototype): Informs the compiler about the function's name, return type, and parameters.
- Syntax: returnType functionName (parameterList);
- Example: int sum(int, int);
Function Definition: Contains the code that performs the function's task.
- Syntax:
```
returnType functionName (parameterList) {
    body of the function
}
```
Function Call: Executes the function's code.
- The function name must match exactly the name in the prototype and definition.
- The number and data types of parameters passed must match the definition.
- If the function returns a value, it must be assigned to a variable of the same data type.

Function Return Types

void: Indicates the function does not return a value.
Data Type: Function returns a value of that type (e.g., int, float, char).

Function Parameter List

Formal Parameters: Variables declared in the function definition that receive values from the function call.
Actual Parameters: Values passed to the function during the function call.

Function Types Based on Data Flow

Accepting Parameters and Returning a Value: Typical function.
Accepting Parameters and Not Returning a Value: Performs a task without returning a specific value.
Not Accepting Parameters and Returning a Value: Performs a task and provides a result.
Not Accepting Parameters and Not Returning a Value: Performs a task without providing a result.

Functions vs. Macros

Macros:
- Processed by the preprocessor, not compiled.
- No type checking.
- Faster execution.
- Useful for small code snippets that are used frequently.
- Do not check for errors during compilation.
Functions:
- Compiled by the compiler.
- Type checking is performed.
- Slower execution.
- Useful for larger blocks of code that are used repeatedly.
- Compile-time errors are detected.
- Safer than macros due to type checking.

Macro Example

#define COLLEGE printf("*****SENECA COLLEGE*****")
#define CUBE(x) x*x*x

Conclusion

Functions provide structure and reusability in C programming. They are crucial for developing modular, organized, and efficient code. Understanding the types and components of functions enables you to write effective and maintainable C programs.