C Programming: Memory Basics and Pointer Arithmetic

Memory Basics

• Memory stores information for the computer.
• Variables are assigned memory space based on their type when declared.
• Uninitialized variables hold whatever value is at their memory location.
• It's essential to initialize variables to give them a desired value.

Variable Declaration and Initialization

• Declaring variables without initialization can lead to unpredictable values.
• Example: a program demonstrating variables without initialization can print unexpected values.

Sizeof Operator

• The sizeof operator determines the memory size of variables or data structures.
• Example: sizeof(array) returns 40 for an array of 10 integers.

Memory Address of Variables

• The & operator fetches the memory address of a variable.
• Example: &c returns the memory location of a char variable c.

Pointers

Pointer Basics

• A pointer is a variable that holds a memory address.
• Declared with a type and an asterisk (*).
• Example: float *p_euros; declares a pointer to a float.

Pointer Initialization

• Assign the address of a variable to a pointer.
• Example: p_euros = &euros; assigns the address of euros to p_euros.

Pointers and Arrays

• Pointers can hold the address of the first element of an array.
• Example: a = array; assigns the address of the first element of array to a.

Dereferencing Pointers

• Use the dereference operator (*) to access the value at the pointer's address.
• Example: *point1 accesses the value of var1 through the pointer point1.

Manipulating Memory with Pointers

• Pointers can be reassigned to different variables.
• Example: outcome is reassigned to point to group1 and then group2.

Pointer Arithmetic

Basic Pointer Arithmetic

• Incrementing a pointer makes it point to the next memory location.
• Example: pa is incremented to point to the next short int in the array.

Pointer Arithmetic Operations

• Pointers can be incremented, decremented, or modified using arithmetic operators.
• Example: pa = pa + 2 increments the pointer to point to the third element in the array.