C Programming: Functions, Scope, Arrays, and Strings

Functions and Scope

Functions in C encapsulate a set of instructions. You define a function to perform specific tasks and call it to execute those tasks.

Defining and Calling Functions

Example of a simple function definition and how to call it:

int add(int a, int b) {
    return a + b;
}
        
int result = add(3, 5);  // result will be 8

Function Prototypes

Prototypes declare the function's existence before its actual definition:

int add(int a, int b);  // Function prototype

Function Arguments and Return Values

Arguments are passed by value. To modify values, use pointers:

void modify(int *x) {
    *x = 100;
}

Scope of Variables

Variables in C can be local or global:

int globalVar = 10;  // Global variable

void exampleFunction() {
    int localVar = 20;  // Local variable
}

Recursion

Recursive functions call themselves to solve problems:

int factorial(int n) {
    if (n <= 1)
        return 1;
    else
        return n * factorial(n - 1);
}

Arrays and Strings

Arrays

Arrays store multiple elements of the same data type:

int numbers[5];  // Array of 5 integers
int numbers2[3] = {1, 2, 3};  // Initialized array

Accessing Array Elements

Index notation starts at 0:

int value = numbers[0];  // Accesses the first element

Strings

Strings are arrays of characters:

char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
char message[] = "Welcome";

String Functions

Standard library functions for string manipulation:

char str1[10] = "Hello";
char str2[10] = "World";

int length = strlen(str1);  // Length of str1
strcpy(str1, str2);         // Copy str2 to str1

Input and Output of Strings

Read and write strings using standard I/O functions:

char name[20];
printf("Enter your name: ");
scanf("%19s", name);  // Reads up to 19 characters

Functions and scope in C allow for modular code with local and global variable scopes, along with recursion for solving repetitive tasks. Arrays and strings provide data structures and string manipulation functions essential for many applications.

Continue exploring C programming with practice exercises and further resources:

Learn-C.org

GeeksforGeeks - C Programming

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C Language Lecture# 5 & 6