More Related Content
Similar to 2-Concept of Pointers in c programming.pptx (20)
Recently uploaded (20)
2-Concept of Pointers in c programming.pptx
- 1. Pointers 1. Introduction to Pointers 2. Call by value and call by reference
- 2. 1. An Introduction to Pointers • A pointer can be used to store the memory address of other variables, functions, or even other pointers. • The use of pointers allows low-level memory access, dynamic memory allocation, and many other functionality in C. • As the pointers store the memory addresses, their size is independent of the type of data they are pointing to.
- 3. • Syntax Datatype * ptr; where • ptr is the name of the pointer. • datatype is the type of data it is pointing to.
- 4. Pointer Declaration • In pointer declaration, only declares the pointer but do not initialize it. To declare a pointer ( * ) dereference operator is used before its name. Example: int *ptr;
- 5. Pointer Initialization • Pointer initialization is the process where we assign some initial value to the pointer variable. • We generally use the ( & ) addressof operator to get the memory address of a variable and then store it in the pointer variable. • Example int var = 50; int *ptr; ptr = &var; Or in a single step we can declare and initialize as follows int *ptr = &var;
- 6. Dereferencing • Dereferencing a pointer is the process of accessing the value stored in the memory address specified in the pointer. • We use the same ( * ) dereferencing operator that we used in the pointer declaration.
- 7. Example Void main() { int i = 5; int *ptr; ptr = &i; printf(“i = %dn”, i); Printf(“&i = %pn”, &i); printf(“*ptr = %dn”, *ptr); printf(“ptr = %pn”, ptr); getch(); } Output: i = 5 &i = affed0 *ptr = 5 ptr = effff5e0
- 8. 2. Call by value and call by reference Call By Value • In call by value method of parameter passing, the values of actual parameters are copied to the function’s formal parameters. – There are two copies of parameters stored in different memory locations. – One is the original copy and the other is the function copy. – Any changes made inside functions are not reflected in the actual parameters of the caller.
- 9. Example of Call by Value // C program to illustrate call by value #include <stdio.h> // Function Prototype void swapx(int x, int y); // Main function int main() { int a = 10, b = 20; // Pass by Values swapx(a, b); printf("In the Caller:na = %d b = %dn", a, b); return 0; } // Swap functions that swaps // two values void swapx(int x, int y) { int t; t = x; x = y; y = t; printf("Inside Function:nx = %d y = %dn", x, y); } Output Inside Function: x = 20 y = 10 In the Caller: a = 10 b = 20 Thus actual values of a and b remain unchanged even after exchanging the values of x and y in the function.
- 10. Call by Reference • In call by reference method of parameter passing, the address of the actual parameters is passed to the function as the formal parameters. – Both the actual and formal parameters refer to the same locations. – Any changes made inside the function are actually reflected in the actual parameters of the caller.
- 11. Example of Call by Reference // C program to illustrate Call by Reference #include <stdio.h> // Function Prototype void swapx(int*, int*); // Main function int main() { int a = 10, b = 20; // Pass reference swapx(&a, &b); printf("Inside the Caller:na = %d b = %dn", a, b); return 0; } // Function to swap two variables // by references void swapx(int* x, int* y) { int t; t = *x; *x = *y; *y = t; printf("Inside the Function:nx = %d y = %dn", *x, *y); } Output Inside the Function: x = 20 y = 10 Inside the Caller: a = 20 b = 10 Thus actual values of a and b get changed after exchanging values of x and y.