Unit III: Arrays and Pointers

Course: Programming with C (SEC)
Code: CASEC101

Definition and Array Processing

An array is a fixed-size collection of elements of the same data type stored in contiguous memory locations.

• Definition: Arrays are defined by specifying the base type, name, and size in square brackets.
• Array Processing: Elements are accessed via an index, typically using loops for efficiency.
• Passing Arrays: When an array is passed to a function, the function receives the address of the first element.

Multidimensional Arrays and Strings

C supports complex data structures by nesting arrays or treating them as character sequences.

• Multidimensional Arrays: Commonly used for matrices; data is stored row by row (Row-major order).
• Arrays and Strings: Strings are essentially character arrays terminated by a null character (\0).

Pointers: Addresses and Declarations

Pointers are variables that store the memory address of another variable.

• Pointer Declaration: Uses the asterisk (*) symbol to denote a pointer type (e.g., int *ptr).
• Addresses: The address-of operator (&) is used to retrieve the memory location of a variable.

Pointers and Function Arguments

Using pointers as arguments allows a function to modify the caller's variables directly.

• Passing Pointers: Also known as "Call by Reference," this avoids copying large amounts of data.
• Function Arguments: Enables the return of multiple values through the modified pointers.

Address Arithmetic and Pointer Arrays

Pointers can be manipulated using mathematical operations to traverse memory.

• Address Arithmetic: Incrementing a pointer moves it to the next valid address based on its data type.
• Pointers and One-dimensional Arrays: The array name itself acts as a constant pointer to the first element.
• Character Pointers and Functions: Frequently used for efficient string manipulation and searching.
• Pointer Arrays: An array where each element is itself a pointer.

Pointers to Pointers and Function Pointers

Advanced pointer concepts allow for dynamic and complex memory structures.

• Pointers to Pointers: A variable that stores the address of another pointer.
• Initialization of Pointer Arrays: Often used for arrays of strings where each pointer points to a string literal.
• Pointers to Multidimensional Arrays: Specialized pointers used to navigate through matrix rows and columns.
• Pointers to Functions: Storing the address of a function in a variable to call it dynamically.

Command Line Arguments

Arguments can be passed to the main function at the time of program execution.

• Mechanism: Uses parameters like argc (argument count) and argv (argument vector/array of strings).
• Passing Functions: Functions can be passed to other functions as parameters using pointers.