Introduction :

Welcome to my first series on #Hashnode where I will be documenting my journey of learning C++ from scratch to advance to develop my programming skills and later make some interesting projects. In this blog, I will be sharing what I learnt in C++ since I wrote my previous blog . In this tutorial, we can study the variables and comments withinside the C++ language. In our last lesson, I mentioned the primary shape of a C++ program, in which we understood the operation of the C++ code line through the line. Do check it out to be up to date with what I will be sharing in this one.

Variables in C++ :

Variables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

int - stores integers (whole numbers), without decimals, such as 123 or -123
double - stores floating point numbers, with decimals, such as 19.99 or -19.99
char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
string - stores text, such as "Hello World". String values are surrounded by double quotes
bool - stores values with two states: true or false

Syntax for Declaring Variables in C++

Data_type Variable_name = Value;
Ex: int a=10; char ch = ‘p’;
Ex: float a= 1.1 , b=6.5;

Rules For Declaring Variables in C++

Variable names in C++ can range from 1 to 255 characters.
All variable names must begin with a letter of the alphabet or an underscore(_).
After the first initial letter, variable names can also contain letters and numbers.
Variable names are case-sensitive i.e it is treated differently depending on whether it is in capital or lower-case text.
No spaces or special characters are allowed.
You cannot use a C++ keyword (a reserved word) as a variable name.

Scope of Variables in C++

In general, the scope is defined as the extent to which something can be worked with. In programming also the scope of a variable is defined as the extent of the program code within which the variable can be accessed or declared or worked with. There are mainly two types of variable scopes:

Local Variables: Variables defined within a function or block are said to be local to those functions.
- Anything between ‘{‘ and ‘}’ is said to be a block.
- Local variables do not exist outside the block in which they are declared, i.e. they can not be accessed or used outside that block.
- Declaring local variables: Local variables are declared inside a block.
Global Variables: As the name suggests, Global Variables can be accessed from any part of the program.
- They are available throughout the lifetime of a program.
- They are declared at the top of the program outside all of the functions or blocks.
- Declaring global variables: Global variables are usually declared outside of all of the functions and blocks, at the top of the program. They can be accessed from any portion of the program.

For example, consider this code snippet --- it shows an example of a variable "sum" taken as an integer variable, which will store a value 5, and writing sum after the "cout" statement will show us the value of "sum" on the output window i.e 5.

#include<iostream>
using namespace std;

int global_variable = 2; 

int main(){
    int local_variable = 3;
    int sum = 5;
    cout<< "The value of variable int sum is "<< sum;
    return 0;
}

Comments in C++ :

A well-documented program is a good habit for a programmer. Programs are easier to read and easier to debug. Comments are an important part of good documentation.

In computer programming, comments are programmer-readable explanations or annotations in the source code of a computer program.
Comments are statements that are not executed by the compiler and interpreter.

There are two ways to write comments :

Single-Line Comments: 1^st way is to use" //" before a single line of text to make it unparsable by the compiler.

Multi-Line Comments: 2^nd way is to use "/*" as the opening and "*/" as the closing of the comment. We then write text in between them. It includes multiple statements in the form of non-executable texts for better readability.

For example :

This program consists of both single-line and multi-line comments that do not affect the outcome of the code. Compiling and executing this program will just print the statement - "Comments are easy".

#include<iostream>
using namespace std;
// This is a single line comment 
/* this
is 
a 
multi
line 
comment */
int main(){
   cout<< "Comments are easy"<< sum;
    return 0;
}

Congratulations!

You just learnt about variables and comments in C++ !!!

Thank you for joining me in my quest to conquer C++. In the next blog, we’ll be talking more about the different Data Types in a C++ program, see you there, till then keep coding and keep learning.

Credit To The Following Resource I Referenced :

Atharva Salitri's Blog