Prerequisite Topics and Concepts to Learn Pointers in C
Before diving into pointers, it is essential to have a solid understanding of the following concepts:
1. Variables and Memory
Key Points:
A variable is a named location in memory used to store data.
Variables have:
Name: Identifier used in the program.
Type: Specifies the kind of data stored (e.g.,
int,float).Value: The actual data stored in the memory.
Address: The location of the variable in memory (retrieved using
&in C).
Example:
#include <stdio.h>
int main() {
int x = 10; // Declare an integer variable
printf("Value: %d\n", x); // Prints the value of x
printf("Address: %p\n", &x); // Prints the memory address of x
return 0;
}
2. Data Types in C
Key Points:
Understand different data types and their sizes in memory.
Common data types:
int: Integer values.
float: Floating-point values.
char: Single characters.
double: Double-precision floating-point values.
Example:
#include <stdio.h>
int main() {
int a = 5;
float b = 3.14;
char c = 'A';
printf("Size of int: %zu bytes\n", sizeof(a));
printf("Size of float: %zu bytes\n", sizeof(b));
printf("Size of char: %zu bytes\n", sizeof(c));
return 0;
}
3. Memory Layout of a Program
Key Points:
Learn about the four memory regions:
Code Segment: Stores the compiled code of the program.
Stack: Stores local variables and function call data.
Heap: Stores dynamically allocated memory.
Global/Static Segment: Stores global and static variables.
4. Arrays
Key Points:
Arrays are a collection of elements stored in contiguous memory locations.
Each element can be accessed using its index.
The name of the array represents the base address of the array.
Example:
#include <stdio.h>
int main() {
int arr[3] = {10, 20, 30};
printf("First element: %d\n", arr[0]);
printf("Base address of array: %p\n", arr);
return 0;
}
5. Functions
Key Points:
Functions allow modular programming by dividing code into reusable blocks.
Understand pass by value (copying value to the function) and pass by reference (modifying the original variable using pointers).
Example (Pass by Value):
void changeValue(int x) {
x = 20; // Modifies local copy, not the original variable
}
int main() {
int a = 10;
changeValue(a);
printf("Value of a: %d\n", a); // Prints 10
return 0;
}