C++ Basics — Part I (for beginner’s)

C++ is a general-purpose programming language.
(and a lot more)

Before diving into code you must have compiler installed in your system.

Compiler — A program that converts High Level Language(HLL) into Low Level Language (LLL).

HLL :

int fib(int n) {
   int store[n+2];
   
   store[0] = 1;
   store[1] = 1;
   int i;  
   for(i=2;i<n;i++) {
       store[i] = store[i-1] + store[i-2];
   }
   return store[n-1];
}
// Any language that you can code in, and is very close to "English" (a natural language) which is easy for a human to read, write and understand.

LLL :

mov edx, [esp+8]
cmp edx, 0
ja @f
mov eax, 0
ret
// Commands or functions in the language map closely to processor instructions.

Windows Users : Install CodeBlocks (IDE) from here
Linux Users : Install g++ (highly recommended) and a CodeEditor (Sublime or VSCode)
Lazy Users : (yes lazy) : Can use online IDE’s , hackerearth, ideone .. etc.

“I recommend you to always refrain from online IDE’s especially during a contest”

before we start, you must know that a C++ file has extension ‘cpp’, while a C file has extension ‘c’.

Let’s Start

#include<iostream>
using namespace std;
int main() {
    // A simple program to print "Hello World"
    cout<<”Hello World!”;
    return 0;
}
Output: Hello World!

Now with explanation

#include<iostream>        // iostream is a header file, it contains 
                          // definition of cin & cout
using namespace std;      // if this were not used then we'd have to
                          // write std::cout<<"abcd"; in the program
int main() {              // declaration of function with name
                          // 'main' and return type of integer.
                          // the definition is found within "{}"
    cout<<"Hello World!"; // cout prints output on the terminal
                          // notice - '<<' this is an operator
                          // notice - '//' statements beginning with
                          // these characters do not get executed,
                          // they are used for comments
    return 0;             // function main would return 0
                          // (an integer)
}

Let’s Math

#include<iostream>
using namespace std;
int main() {
    cout << "3 + 2 = " << 3+2 << endl;
    cout << "3 - 2 = " << 3-2 << endl;
    cout << "3 * 2 = " << 3*2 << endl;
    cout << "3 / 2 = " << 3/2 << endl;
    cout << "10 / 3 = " << 10/3 << endl;
    cout << "10.0 / 3 = " << 10.0/3 << endl;
    return 0;
}
OUTPUT : 
3 + 2 = 5
3 - 2 = 1
3 * 2 = 6
3 / 2 = 1
10 / 3 = 3
10.0 / 3 = 3.33333

Notice 3 / 2 = 1 and 10 / 3 = 3, yes you guessed it correct, only the integral part is retained.
This happens because by default data-type is integer. Unless specified like in example 10.0 / 3 = 3.33333 (any operation that includes a decimal will result in one)

Book : Balaguruswamy OOPs with C++ (recommended)

Please go through chapter 3, 4 for a detailed content.
“Recommended”

All the chapters are important and would be covered in your course in span of one to two semesters. I cannot cover everything in this blog hence provided you with a resource.

Topics that you must know before moving forward are:

1. Variables (data type)
2. Loops (for, while, do)
3. IF ELSE
4. Arrays & Matrix
5. Functions

Important: To learn C/C++ you must read a book and run your code.
There is no other easy way.
(do not watch videos for this, start reading the book)

The next part would focus on getting a good grip on the language.