Introduction to Arrays in C

Introduction to Arrays in C

• Arrays store a collection of elements of the same data type.
• Elements are accessed using an index, starting from 0.
• Array size is fixed at compile time.
• Memory is allocated contiguously for array elements.

Declaration and Initialization

• Syntax: data_type array_name[array_size];
• Example: int numbers[5]; declares an integer array named 'numbers' with a size of 5. Crucially, int numbers; is incorrect and declares a single integer variable.
• Initialization:
  • During declaration: int numbers[5] = {1, 2, 3, 4, 5};
  • After declaration: numbers[0] = 10; assigns 10 to the first element. numbers = 10; is incorrect.
• Initialization with fewer values: int numbers[5] = {1, 2}; Initialises the first two elements, the rest are set to zero (or, for floats, 0.0).
• Accessing elements: numbers[2], numbers[4] accesses the third and fifth element (indexing starts at 0). numbers and numbers (repeated) are also incorrect.

Array Size and Bounds

• Array size is fixed at compile time.
• Trying to access an element outside the array bounds results in undefined behavior.
• Example: numbers[5] is out of bounds if the array size is 5. numbers in the example is incorrect.
• C does not automatically check array bounds. Programmers must ensure indexes are within the valid range.

Array Traversal

• Iterating through array elements with loops (e.g., for, while) is common.
• Example:

for (int i = 0; i < 5; i++) {
    printf("%d ", numbers[i]);
}

Multidimensional Arrays

• Arrays with more than one dimension can be declared.
• Syntax: data_type array_name[row_size][column_size];
• Example: int matrix[3][4]; declares a 2D array (3 rows, 4 columns). int matrix; is incorrect.
• Accessing elements: matrix[1][2] accesses the element in the second row and third column. matrix is incorrect.
• Initialization similar to 1D arrays.

Array as Function Arguments

• Passing arrays to functions is efficient.
• By default, arrays are passed by reference. Changes inside the function affect the original array.
• Example:

void printArray(int arr[], int size) {
    // Code to print the array
}

Pointers and Arrays

• Arrays and pointers are closely related in C.
• An array name decays to a pointer to its first element in expressions.
• Example: arr is equivalent to &arr[0]. arr is equivalent to &arr is also incorrect
• Pointer arithmetic can be used to access array elements.

String as Character Arrays

• Strings in C are represented as arrays of characters (char).
• The null terminator ('\0') marks the end of the string.
• Example: char str[] = "Hello"; creates an array to hold "Hello\0" (size is implicitly 6).
• Libraries like string.h provide functions for string manipulation.

Dynamic Memory Allocation

• malloc, calloc, realloc are used for dynamic arrays.
• malloc allocates memory, calloc initializes memory to zero, realloc changes memory size.
• Example:

int *dynamicArray;
int size = 10;
dynamicArray = (int*)malloc(size * sizeof(int));

• free is essential to release memory allocated with malloc.

free(dynamicArray);

Important Considerations

• Be mindful of array bounds to avoid errors.
• Dynamic arrays need explicit memory management (e.g., malloc, realloc, free).
• Choose a method (static or dynamic) based on expected array size and flexibility needs.

This quiz covers the basics of arrays in C programming, including declaration, initialization, and accessing elements. Test your understanding of array sizes, bounds, and memory allocation in C. Prepare to enhance your coding skills with this fundamental topic!