Unit II: Functions and Program Structure

Course: Programming with C
Code: CADSM101

Defining and Accessing Functions

A function is a self-contained block of code that performs a specific task. Using functions helps in modularizing code and promoting reusability.

• Definition: Includes the function name, return type, and the body of the function.
• Accessing: Functions are "called" from other parts of the program, such as main(), to execute their tasks.

Passing Arguments and Data Types

Functions can receive data through arguments. In C, you must specify the data type for each argument passed to a function.

• Actual Arguments: The values passed to the function during a call.
• Formal Arguments: The variables declared in the function definition to receive those values.

Function Prototypes and Return Types

A Function Prototype tells the compiler about the function's name, return type, and parameters before the actual definition is provided.

• Non-integer returns: Functions can return types other than int, such as float, double, or char.

Storage Classes

Storage classes define the scope, visibility, and lifetime of variables within a C program.

Scope Rules and Block Structure

The scope refers to the region of the program where a variable is accessible.

• Local Scope: Variables declared inside a block or function are only accessible within that block.
• Global Scope: Variables declared outside all functions are accessible everywhere.
• Block Structure: C supports nested blocks using curly braces {}, where inner blocks can access outer variables (unless shadowed).

Recursion in C

Recursion is a technique where a function calls itself to solve smaller instances of the same problem.

Example: Factorial of n is n * Factorial(n-1).

• Must have a Base Case to prevent infinite loops.
• Useful for problems like Tower of Hanoi and Fibonacci series.

The C Preprocessor and Header Files

The preprocessor processes the source code before it is passed to the compiler.

• Header Files: Files ending in .h (like stdio.h) containing function declarations and macros.
• Macros: Used for defining constants or small code snippets using #define.