Unit III: Arrays and Pointers

Course: Programming with C
Code: CADSM101

Array Definition and Processing

An array is a collection of data items of the same type stored in contiguous memory locations.

• Definition: Arrays are defined by specifying the data type and the number of elements (e.g., int marks[5];).
• Processing: Elements are accessed using an index starting from 0.
• Passing to Functions: Entire arrays can be passed to functions to perform operations on the data set.

Multidimensional Arrays and Strings

• Multidimensional Arrays: C supports arrays of arrays, commonly used for matrices (2D arrays).
• Strings: In C, a string is an array of characters terminated by a null character (\0).

Pointers: Addresses and Declarations

A pointer is a variable that stores the memory address of another variable.

• Declaration: Pointers are declared using the * operator (e.g., int *ptr;).
• Addresses: The & operator is used to get the address of a variable.

Pointers and Function Arguments

Pointers allow functions to modify the original value of variables in the calling function, known as Call by Reference.

• Passing Pointers: Instead of passing a value, the address is passed to the function.
• Utility: This is essential for returning multiple values from a function or manipulating large data structures efficiently.

Address Arithmetic and Arrays

C allows arithmetic operations on pointers, which is closely linked to how arrays work.

• Pointer Arithmetic: Adding an integer to a pointer moves it to the next memory location of its base type.
• One-dimensional Arrays: The name of an array acts as a constant pointer to its first element.
• Character Pointers: Often used to handle strings and dynamic text efficiently.

Pointer Arrays and Pointers to Pointers

• Pointer Arrays: An array where each element is a pointer (e.g., used for arrays of strings).
• Pointers to Pointers: A variable that stores the address of another pointer.
• Initialization: Pointer arrays can be initialized with addresses of variables or string literals.

Command Line Arguments and Function Pointers

• Command Line Arguments: Parameters passed to the main() function from the terminal (argc and argv).
• Pointers to Functions: Variables that store the starting address of executable code.
• Passing Functions: Function pointers can be passed as arguments to other functions, enabling callbacks.