NOT SO COMMON C++

Hello Techiez, today in this post i'll be discussing about some shortcuts and some methods in C++ which are we generally miss while studying C++. This post will be useful for both C++ beginners  as well for experienced programmers.

So lets explore.

1. Convert a decimal value to hexadecimal/octal.

Program: 

#include<iostream>

using namespace std;

int main()

{

    int num1=300;

    cout<<hex<<num1;   //hex is an manipulator used to convert num1 into hexadecimal value

}

Output:

12c

Same program can be used to convert :

        (a)decimal to octal, just change "hex" to "oct" and 

        (b)for octal/hexadecimal to decimal, just change "hex"/"oct" to  "dec" (before a hex/oct number).

lets see an example for part '(b)'

Program:

#include<iostream>

using namespace std;

int main()

{

    int num1=01067;         // 01067 is an octal for 567

    cout<<dec<<num1;

}

Output:

567

Another way to do the same:

Program :

#include<iostream>

#include<iomanip>                       // for using setbase() using iomanip is necessary

using namespace std;

int main()

{

    int num1=345;

    cout<<setbase(16)<<num1;      // to convert num1 int octal change "16" to "8"

    return 0;

}

similarly to convert hexadecimal(or octal) value to decimal use setbase(2) before the hexadecimal value.

2. Different ways to Initialize and not to Initialize an array.

Yes there are a number of ways to initialize an array.

(a)  int array[6];                           // CORRECT

(b)  int array[6]={9,4,6,2,3,5};   //CORRECT

(c)  int array[6]={9,4};               //CORRECT

(d)  int array[];                           //INCORRECT

(e)  int array[2]={9,4,6,2,7,8};  //INCORRECT

(f)  int array[]={2,3,6,7};           //INCORRECT

3. Structure Initialization.

Structures can also be initialized, the structure initiator is enclosed in curly brackets and contains different values which w.r.t the subsequent fields.

Program:

#include<iostream>

using namespace std;

struct Student

{

    string name;

    int age;

    int Std;

};

int main()

{

    struct Student student={"Rahul",12,6};           // This is structure initialization

    cout<<student.name<<endl;

    cout<<student.age<<endl;

    cout<<student.Std<<endl;

}

Output:

Rahul

12

6

4. Structure can be a field inside an another Structure.

Lets see an example to understand this.

Program:

#include<iostream>

#include<iomanip>

using namespace std;

struct Date

{

    int day;

    int month;

    int year;

};

struct Emp

{

    string name="Rahul";

    int age=26;

    struct Date dateofjoin={12,9,2011};    //Structure as a field inside an another structure

};                                                               

int main()

{

    struct Emp emp;

    cout<<emp.name<<endl;

    cout<<emp.age<<endl;

    cout<<emp.dateofjoin.day<<"-"<<emp.dateofjoin.month<<"-"<<emp.dateofjoin.year<<endl   

}

Output:

Rahul

26

12-9-2011

Now, what is that "emp.dateofjoin.day" ?

Here we are using two subsequent operators(selection operator) to dig deeper into the structure.

We are first selecting a structure within a structure and then the desired field of the inner structure.

5. Can we assign values to pointer?

(a) We cannot assign a literal value to the pointer.

Program:

int *p;

p=45678; // this is will show error beacuse 45678 is a literal value

Output:

error

(b) we can assign some meaningful value to pointer.

Program:

int *p;

p=&i;   //assigning the pointer with the value which points to already existing variables.

(c) we can also assign zero or null to the pointer

Program:

int *p;

p=0;          // zero is the only literal we can assign to pointer

    OR 

p=NULL;    // but to use this you have to use #include<cstring>

6. Something more on Pointers.

There are some more things I would like to point out about the Pointers which may b useful to useful to use.

• If we use the name of an array(without indices), it is equivalent to the pointer pointing to the first element of the array. i.e  

                              int *p, array[10];
                           
                     here,     "array" is equivalent of using "&array[0]".
       But remember you can only use "array" to point to the first element in the array(i.e array[0]).

• Adding an integer value to a pointer gives back a Pointer.
• Subtracting an integer value from a pointer gives back a Pointer.
• Subtracting a pointer from another pointer gives back an Integer.
• comparison of two pointers for equality or inequality is also meaningful and can be practiced in C++.

Any other operation is either prohibited or meaningless.



Lets see an example:

Program:

int *ptr1, *ptr2;

int arr[3];

ptr1=arr;

ptr2=ptr1;

are you able to understand the flow of program, consider this diagram to get a better idea about what happened in the above code

.

Now as we discussed earlier about the addition on pointer , we will see an example on it.

ptr1=ptr1+1;                        // w.r.t the above example

So, what will happen now ....????
As we discussed earlier addition of a pointer and an integer gives you back a POINTER.
When we are adding 1 to the ptr1 then ptr1 would be increased by (1*sizeof(int)) and now ptr1 will point to arr[1].

I hope all this info on C++ was helpful to you, i'll be posting more post like this one on C++ in coming time.

For any queries leave comment below.

Keep Exploring.