Example C Pointer

main.c

#include <stdio.h>

int main() {
    // 1. Declaring a Pointer
    int *ptr; // Pointer to an integer

    // 2. Assigning Address to a Pointer
    int var = 10;
    ptr = &var; // ptr now holds the address of var

    // 3. Dereferencing a Pointer
    int value = *ptr; // value is now 10 (the value of var)

    // 4. Modifying Value via Pointer
    *ptr = 20; // var is now 20

    // Example Output
    printf("Value of var: %d\n", var);        // Output: 20
    printf("Address of var: %p\n", (void*)&var); // Output: Address of var
    printf("Value via pointer: %d\n", *ptr);   // Output: 20

    return 0;
}

• int var; declares an integer variable.
• var = 10; assigns the value 10 to var.
• int *ptr; declares a pointer to an integer.
• ptr = &var; assigns the address of var to ptr.

In programming, the terms L-value and R-value refer to different types of expressions:

1. L-value (Left value): Refers to a variable (can be assigned).

   • An L-value refers to an expression that has a memory address and can appear on the left side of an assignment.
   • It represents a variable that can be modified.
   • Example: var in var = 10; is an L-value because it can be assigned a value.

2. R-value (Right value): Refers to a value or expression (cannot be assigned).

   • An R-value refers to an expression that does not have a memory address and typically represents a temporary value.
   • It can appear on the right side of an assignment but cannot be assigned a value.
   • Example: 10 in var = 10; is an R-value because it is a literal value that cannot be modified.