Pointers

Pointers as Function Arguments - Call by Reference

Call by Value

#include <iostream>
using std::cout;
using std::endl;


void Increment (int a)
{
    a = a + 1;
    cout << "Address of Variable a in increment = " << &a << endl;
}

int main()
{
  int a;
  a = 10;

  cout << "Address of Variable a in Local Scope = " << &a << endl;
  Increment(a);

  cout << "a = " << a << endl;

}

Output:

Address of Variable a in Local Scope = 0x7ffee34ae60c
Address of Variable a in increment = 0x7ffee34ae5dc
a = 10

Pass by Pointer

#include <iostream>
using std::cout;
using std::endl;


void Increment (int *p)
{
    *p = *p + 1;
}

int main()
{
  int a;
  a = 10;

  Increment(&a);

  cout << "a = " << a << endl;

}

Output:

a = 11

Pointers and Arrays

Example Code

#include <iostream>
using std::cout;
using std::endl;

int main()
{
  int A[] = {2,4,5,8,1};
  cout << "Return Address of A: " << endl;
  cout << A << endl;

  cout << &A[0] << endl;

  cout << "Return Value of A: " << endl;
  cout << A[0] << endl;
  cout << *A << endl;

}

Output

Return Address of A: 
0x7ffeeb89e5f0
0x7ffeeb89e5f0
Return Value of A: 
2
2

Arrays as Functions Arguments

Example 1

#include <iostream>
using std::cout;
using std::endl;


int SumOfElements(int A[], int size)
{
  int sum = 0;
  for(int i = 0; i< size; i++)
  {
    sum += A[i];
  }

  return sum;
}


int main()
{
  int A[] = {1,2,3,4,5};
  int size = sizeof(A)/sizeof(A[0]);

  int total = SumOfElements(A, size);

  cout << "Sum of the Elements: " << total << endl;
 
}

Output

Sum of the Elements: 15

Example

Output

Example

Output

Character Arrays and Pointers Part 1

How to store Strings Example 1

#include <iostream>
using std::cout;
using std::endl;


int main()
{
    char C[4];
    C[0] = 'J';
    C[1] = 'o';
    C[2] = 'h';
    C[3] = 'n';

    cout << C << endl;
}

Output:

John ���

• Notice all the Extra Characters!

Example 2

#include <iostream>
using std::cout;
using std::endl;


int main()
{
    char C[5];
    C[0] = 'J';
    C[1] = 'o';
    C[2] = 'h';
    C[3] = 'n';
    C[4] = '\0';

    cout << C << endl;
}

Output:

John

Example 3

• An Array of 20, which is way bigger than the number of Char we include in the Array

• The NULL termination will end once found (\0)

#include <iostream>
using std::cout;
using std::endl;

int main()
{
    char C[20];
    C[0] = 'J';
    C[1] = 'o';
    C[2] = 'h';
    C[3] = 'n';
    C[4] = '\0';

    cout << C << endl;
}

Output:

John

Arrays and Pointers are different types that used in similar manner

Arrays are always passed to function by reference (only pass the base address)

Another Example

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;

void print_array(char* C)
{
    int i = 0;
    while(C[i] != '\0')
    {
        cout << "index: " << i << ": " << C[i] << " " << "\n";
        i++; 
    }
    cout << endl;
}

int main()
{
    char C[20] = "Hello";
    print_array(C);
    
}

Output

index: 0: H 
index: 1: e 
index: 2: l 
index: 3: l 
index: 4: o 

Character Arrays and Pointers Part 2

Example Code

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;

void print_array(char C[])
{
    while(*C != '\0')
    {
        cout << *C;
        C++; 
    }
    cout << endl;
}

int main()
{
    char C[20] = "Hello";
    print_array(C);   
}

Output

Hello

Another Example

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;

void print(char *C)
{
    C[0] = 'A'; // Change value in Array
    while(*C != '\0')
    {
        cout << "C: " << *C << endl;
        C++; 
    }
    cout << endl;
}

int main()
{
    char C[20] = "Hello";
    print(C);   
}

Output

C: A
C: e
C: l
C: l
C: o

Another Example using const keyword

• With the const Keyword, we can’t change/overwrite any positions in the array

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;

void print(const char *C)
{
    // C[0] = 'A'; // Change value in Array
    while(*C != '\0')
    {
        cout << "C: " << *C << endl;
        C++; 
    }
    cout << endl;
}

int main()
{
    char C[20] = "Hello";
    print(C);   
}

Output:

C: H
C: e
C: l
C: l
C: o