23. C Pointers.md

C Pointers

Video Link: https://youtu.be/KGhacRRMnDw
Tutorial Link: https://www.programiz.com/c-programming/c-pointers

Pointer Variables

#include <stdio.h>

int main() {

  int age = 25;

  printf("%p", &age);

  int* ptr = &age;

  printf("\n%p", ptr);

  return 0;
}

Output

0x7ffc875fe0ec
0x7ffc875fe0ec

Access Value using Pointer

#include <stdio.h>

int main() {

  int age = 25;

  int* ptr = &age;

  printf("Address: %p\n", ptr); 

  printf("Value: %d", *ptr);

  return 0;
}

Output

Address: 0x7fff7e4319bc
Value: 25

Change Value using Pointer

#include <stdio.h>

int main() {

  int age = 25;

  int* ptr = &age;

  *ptr = 31;

  printf("%d", age);

  return 0;
}

Output

31

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Programming Task

Create a program to change the value of a variable using a pointer. Here's how the program should work:

• Get input value for a double variable salary.
• Assign the address of salary to a double pointer.

Now use the pointer to

• print the value of salary,
• increase the salary by 2 times,
• print the new salary.

Solution

#include <stdio.h>

int main() {
    double salary;
    
    printf("Enter your salary: ");
    scanf("%lf", &salary);
    
    double* ptr = &salary;
    
    printf("Your Salary: %.2lf\n", *ptr);
    
    double new_salary = *ptr * 2;
    
    printf("Your double salary: %.2lf", new_salary);
}

Output

Enter your salary: 28000.5
Your Salary: 28000.50
Your double Salary: 56001.00

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Programiz Quiz

Q. Which of the following is valid for variable a and pointer p?

Options:

1. *p = &a
2. p = a
3. *p = a
4. p = *a

Answer: 3