C ++

https://code.visualstudio.com/docs/languages/cpp

Terminal > Run Build Task command (Ctrl+Shift+B)

g++ -o main.exe main.cpp utils/greet.cpp

g++ -o main.exe main.cpp utils/greet.cpp calcu/calculation.cpp

run by .\helloworld

• C++ is one of the oldest yet most popular programming languages in the world due to its performance and efficiency.

• It’s often used in building performance-critical applications, video games (especially with Unreal Engine), servers, operating systems, etc.

• To learn C++, you need to learn the syntax (grammar) of the language as well as C++ Standard Library, which is a collection of pre-written C++ code for solving common problems.

• To write C++ applications, we often use an Integrated Development Environment (IDE). The most popular IDEs are MS Visual Studio, XCode, and CLion.

• To run C++ applications, first we have to compile our C++ code to machine code.

• The main() function is the starting point of a C++ program.

• every 3 year new c plus version is comming

• still the most fast and efficient language

• main function is the enrty point of the program

• before the functin name we should specify the type of value is gona return

c++ statnadard libray

iostream name of one of file in the standard library

std => standard library

cout => charactor out, we can output one or more charactor

<< stream insertion operator

>> stream exraction operator

complie to machine code , we ge an executable, but it will run on the same os only, for different os we need tho complie on the diffrent os

• We use variables to temporarily store data in the computer’s memory.

• To declare a variable, we should specify its type and give it a meaningful name.

• We should initialize variables before using them. Using an uninitialized variable can lead to unexpected behavior in our programs since these variables hold garbage values.

• Unlike variables, the value of constants don’t change.

• The common naming conventions used in C++ applications are: PascalCase, camelCase, and snake_case.

• An expression is a piece of code that produces a value. A mathematical (arithmetic) expression consists of an operator (+, -, *, /, %) and two operands.

• Multiplication and division operators have a higher priority than addition and subtraction operators. So, they’re applied first

• We can use parentheses to change the order of operators.

• We use cout (pronounced sea-out) to write characters to the Standard Output Stream which represents the terminal or console window.

• We use cin (pronounced sea-in) to read data from the Standard Input Stream which represents the keyboard.

• We use the Stream Insertion Operator (<<) to write data to a stream.

• We use the Stream Extraction operator (>>) to read data from a stream.

• The Standard Template Library (STL) consists of several files each containing functions for different purposes.

• To use functions in the Standard Library, we should include the corresponding files using the #include directive.

• Using comments we can explain what cannot be expressed in code. This includes why’s, how’s, and any assumptions we made while writing code.

variables

varibale is a name of lacation of a memmory

declare int a;

if not initialized, due to garbage, data currently in memory

int filze_size = 0, counter = 1;

also this works, but not ecouraged

const double pi = 3.14;

act like js const

int file_size // Snake Case

int FileSIze // pascal case

int fileSize // camel Case

int iFileSize // hugarian case (just like pascal case but the data type is in the front) it is very old , not releven but is in the old window code, that time the ede+itor was ot that feature rich

using namespace std;

now you can use cout instead of std::cout

endl to make a new line charactor

• C++ has several built-in data types for storing integers (whole numbers), floating-point numbers (numbers with a decimal point), characters, and Boolean values (true/false).

• Floating-point numbers are interpreted as double by default. To represent a float, we have to add the F suffix to our numbers (eg 1.2F).

• Whole numbers are interpreted as int by default. To represent a long, we have to use the L suffix (eg 10L).

• Using the auto keyword, we can let the compiler infer the type of a variable based on its initial value.

• Numbers can be represented using the decimal, binary, and hexadecimal systems.

• If we store a value larger or smaller than a data type’s limits, overflowing or underflowing occurs.

• Using the sizeof() function, we can see the number of bytes taken by a data type.

• We can use stream manipulators to format data sent to a stream. The most common manipulators are setw, fixed, setprecision, boolalpha, left, and right.

• The Boolean false is represented as 0. Any non-zero number is interpreted as the Boolean true.

• In C++, characters should be surrounded with single quotes.

• Characters are internally represented as numbers.

• A string is a sequence of characters and should be surrounded by double quotes.

• We use arrays to store a sequence of items (eg numbers, characters, etc).

• Array elements can be accessed using an index. The index of the first element in an array is 0.

• When we store a smaller value in a larger data type, the value gets automatically cast (converted to) the larger type. When storing a large value in a smaller data type, we have to explicit cast the value.

• C-style casting involves prefixing a variable with the target data type in parentheses. In C++, we use the static_cast operator.

• C++ casting is safer because conversion problems can be caught at the compile-time. With C-style casting, we won’t know about conversion issues until the run-time

fundamental types

Type	Bytes	Range
short	2	-32768 to 32767
int	4	-2BIllion to 2Billion
long	4	same
long long	8

most usfull is short and int

Type	Bytes	Range
float	4	-3.4E38 to 3.4E38
double	8	-1.7E308 to 1.7E308
long double	8	-3.4E932 to 1.7E4832

most used double (because float sometime result in lost of accuracy)

Type	Bytes	Range
bool	1	true/false
char	1

char a = 'b';

double price = 99.99;

float interestRate = 3.67F; // 3.67F or 3.67f

long file_size = 9000L; // 9000l or 9000L both accepted but L is more used,(if we dont type L this will take it as integer)

char letter = 'a'; // use single qoute for character

bool isValid = true // true/false

we can also use auto , to let the complier infer the type of the variable

auto isValid = true;

int number 1.2;

this will show 1 at terminal

but a better way of intitalization

int number {1.2} /// t his will show compilation errro as float is tried in the int type

int number {} // this will initilize to value 0

number system

demial (base 10) 0-9 255

Binary (base 2) 0, 1 11111111

hexa (base 16) 0-9, A-F FF

int number = 0b11111111;

int number = 0xFF;

unsigned int number = -255; // unsigned cause problem

unsigned int number = 0;

number--;

cout <<number \\this will cause problem

Narrowing

assigneing higher tpe values ot smaller type

int number = 1'000'000;

short another = number;

reverse of it(this is not an issue)

short number 100;

int another {number}

cout << sizeof(int); // size of bytes

#include <limits>

cout << numeric_limits<int>::min() << endl // numeric_limits is a class

<< numeric_limits<int>::max() //this line will let you know the limit of the integer values

what happen if we store value larger than the limit

#include <limits>

int number = numeric_limits<int>::max();

number++;

cout << number; // this will result in smallest value, this is called overflow(the number was too big for it)

#include <limits>


int number = numeric_limits<int>::min()

number--;

cout << number; // this will result in largest value, this is underflow(the nuber was too small for it)

bool isvalid = false;

cout << boolalpha << isValid; // otherwise this wll return 0 on termnal

char for single

string for seq of character

computer reperenst it asnumber is numeric

char ch = 'a'; // use singel qoute for char

cout << ch;

cout << +ch; // this will print the nueric reperesentaion of charactor a

char ch = 98;

cout << ch;

string name = "ajay sharma"; // for sequence of character

#include <string>

string name;

cout << "Enter Your name";

cin >> name;

cout << "Hi " << name; // this will missout naythin after first whitespace

use

#include <string>

string name;

cout << "Enter Your name";

getline(cin, name)

cout << "Hi " << name; // this will show your name

to store list of integer

int numbers[5]; to write an array with the 5 integer values

cout << numbers; // this will print the hexadecimal address of the array

cout << numbers[0]; // this will print out 0

cout << numbers[1]; // this will print out 0 // by default at all places it keep integer 0

int numbers[5];

numbers[1] = 10;

cout << numbers[1];

cout << numbers[5]; this will print the any number that garbage collector found at that time

int numbers[5] = {10,20}

cout << numbers[0]; //

int numbers[] = {10, 20}; // to let the compiler decide how many values need

int x = 1;

double y = 2.0;

int z = x + (int)y; // c style casting,but if conversion cannot be done wi won't know untill run time

int z = x + static_cast<int>(y);// this will show error on compile time if error on conversion(casting)

cout << z;

int x = 10;

int y = 3;

double z = x / y; this will return int, to solve this caste any one value

double z = static_cast<double>(x) / y;

comparison operator

expression is a peiceof code that produce a value

int x = 10;
int y = 15;
boal isValue = x != y;
cout << boolalpha << isValue 

int x = 10;
double y = 15;
boal isValue = x == y; // c automatically convert the lower datatypes to upper data types
cout << boolalpha << isValue

logical variable (&&, ||, !)

int age = 18;
bool isEledgible  = age > 18 && age < 65;   // c check from left to right
cout << boolalpha << isEledgible;

int age = 18;
bool isEledgible  = age > 18 || age < 65;   // c check from left to right, both are checked
cout << boolalpha << isEledgible;

int age = 18;
bool isEledgible  = age > 18 || age < 65;   // c check from left to right, both are checked
cout << boolalpha << !isEledgible; // not logical operator

preority order

() // higest prioritiy

!

&&

||

bool a = true;
bool b = false;
bool c = false;
bool result = b && !a;
bool result = a || b && c;
cout << boolalpha << result;

if statements

int temp = 30;
if (temp < 60)
    cout << "Cold"

int temp = 70;
if (temp < 60)
   cout << "cold";
cout << "warm";

If there is more than one statements in if the use paranthisis

int temp = 70;
if (temp < 60){
   cout >> "new cout"
   cout << "cold";
   }
cout << "warm";

int temp = 70;
if (temp < 60)
   cout << "cold";
else if(temp > 20){
    cout << "else if part"
    }
else
   cout "else part"
cout << "warm";

also we can write in one line

int temp = 70;
if (temp < 60) cout << "cold";
else if(temp > 30) cout << "else if part";
else cout "else part";
cout << "warm";

nested if

int temp = 70;
if (temp < 60)
   cout << "cold";
   if (temp < 60)
    cout << "nested cold";
else if(temp>30){
    cout << "else if part"
    }
else
   cout "else part"
cout << "warm";

int sales = 1'000;
if (sales > 10'000)
   commision = .1;
else
   commision = .05;
 // the below is same as the above 4 lines
double commission = (sales > 10'000) ? .1 : .05;  condidition ? if value is true : if value is false

switch statement(to caire variablle with a set of values)

cin >> input;

switch (input){
    case 1:
        cout << "You selected 1";
        break; // break is must other wise it will print case 2 also even it is not true
    case 2:
        cout << "you selected 2";
        break;
    default:
        cout << "good bye" // as this is the last statement, there is no break statement needed as there is notheing to execute after that

loops

to repeat 1 or more example

for (int i = 0; i < 5; i++)  {   // intial value, condition, increment/decriment,      wrap in braces for more exp, controller
  cout << i <<endl;
}

for (int i = 5; i > 0; i--)  // intial value, condition, increment/decriment,      wrap in braces for more exp
  cout << i <<endl;

int numbers[] = {1,2,3}
for (int i = 0; i < 3; i++)
    cout << numbers[i] << endl;

but we are hardcoding it (ie i < 3)

int numbers[] = {1,2,3,4}
// sizeof(numbers): 16  // this might not same on every os
// sizeof(int): 4
for (int i = 0; i < sizeof(numbers) / sizeof(int); i++)   // now this is dynamic, but there is a newer way in morder cpp
    cout << numbers[i] << endl;

range base for loop

for (int number:numbers)
     cout << number << endl;
     

string name = "Mosh Hamedani";
for (char ch:name) // we can loop over string also
   cout << ch << endl;

while loop

int i = 1;
while (i <= 5){
    cout << i << endl;
    i++;
}  

do while

do{  // braces are requied here
     // do will run atleast one time
}while()

first the do block will execute

then it check for condition in while ,

if condition true, it again enter into do block,

if condition false then the while block will execute

do execute at start and run again untill while is true

when while codition is false, the while block will execute

do{
cout << "Enter a number "
int number; // so take this variable outside of do
cin >> number;
} while (number < 1 || number > 5) // the number is not accsibe here, as in cpp vairable is on ly accible in the scope of the block in wich it declare

int number; // so take this variable outside of do
do{
cout << "Enter a number "

cin >> number;
} while (number < 1 || number > 5) // the number is not accsibe here, as in cpp vairable is on ly accible in the scope of the block in wich it declare

    int i = 1;

    do { // do will execute al least one time
        cout << "i = " << i << endl;
        cout << "do block" << endl;
        i++;
    } while (i < 5);
    {
        cout << "i = " << i << endl;
        cout << "While block " << endl;
    }

break & continue

nested loop

function

if a function doesnot return a value then type void keyword

viod greet(){
    cout << "hell" << endl;
    }

int main(){
    greet()
    cout << "o";
}

void greet(string firstName, string lastName){
    cout << "hell" << firstName " " << lastName << endl;
    }

int main(){
    greet("ajay","sharma")
    cout << "done";
}

parameter the names that define in the function

arguments are the values that is applied to those parameters

void greet(string firstName, string lastName){
    cout << "hell" << firstName " " << lastName << endl;
    }
string full_name(string firstName, string lastName){
    return  firstName + " " + lastName;
    }

int main(){
    greet("ajay","sharma")
    string name = fullname("ajay","Kumar")
    cout << name;
    cout << "done";
}

int max(int first, int second){
    if (first > second)
        return first;
    else
        return second;
}

int max(int first, int second){
    if (first > second)
        return first;
    return second;
}

int max(int first, int second){
    return (first > second) ? first : second;
}

function with default value(should be at the end)

double calculateTax(double income, double taxRate = .2){
    return income * taxRate;
}

fucntion overloading

// in overloading each function should have unique signature
void greet(string name){  // this is valid
    cout << "Hello " << name;
    }
/*
*void greet(string name,string lastname){  // this is not valid, as this has the same signature as the next one
*    cout << "Hello " << name;
 *   }
 
 */
 
 
// signature = name of the function + (number and type of parameter)        here we have name greet and 2 parameter of string type   
void greet(string title, string name){
    cout << "Hello " << title << " " << name;
    }
    
 int main(){
    greet("ajay")
    greet("ajay" , "sharam")
}

passing arguments by value or reference(by default it is passed as value in c)

void increaseNumber(double price){ // as the parameter have the block level scope
    // price = price * 1.2;
    price *= 1.2;
    }
    
    
int main(){
    double price 100;
    increaseNumber(price); // this will act like a copy of price is passed to the function
    cout << price;  //thus this not gaonna change
    }

reference parameter

double& price will act like reference parameter.

void increaseNumber(double& price){ // now this will act as pass by reference
    price *= 1.2;
    }
   
int main(){
    double price 100;
    increaseNumber(price); // the above price will be passed to the function, not the copy
    cout << price;  //due to apprasent in function, thus this gonna change
    }

the above is helpful if we have large amount of data, so copy may decrrease the efficincy

void greet(string& name){
    cout << "Hello " << name;
    }

int main (){
    string name = "aja";
    greet(name);
    cout << name;
    return 0;
    }

void greet(string& name){
    cout << "Hello " << name;
    name = "abc"; //will change the name value in the main function also
    }

int main (){
    string name = "aja";
    greet(name);
    cout << name;
    return 0;
    }

to prevent accidental change of refernce value use const

void greet(const string& name){  // use const so there is no changes by any mistake
    cout << "Hello " << name;
    }

int main (){
    string name = "aja";
    greet(name);
    cout << name;
    return 0;
    }

local and global variable

int taxRate = 20; // global variable

double calculateTax(int sales){
    return sales * taxRate; // this is available in the function as it is in global scope
}



int main (){
    // this is an local variable
    int sales = 10'000;
    double tax = calculateTax(sales);
    cout << tax;
    return 0;
    }

function decalaration

int main(){
    greet("AJ"); // this will throw error as main doesnt know about function greet, in another words it should be define before main
    return 0;
 }
 void greet(string name){
    cout << "Hello " << name;
    }

// function decaleration (function prototype)
void greet(string name)


 int main(){
    greet("aBC");
    return 0;
 }
 
 // function defination
 void greet(string name){
    cout << "Hello " << name;
    }

---

organizing functions in file

HelloWorld/main.cpp

here we are tring to define the greet function in another file

this will be helpfull to make file size small, and we are also able to use it in another files or project

#include <iostream>

using namespace std;

// function decaleration (function prototype)
void greet(string name);

int main(){

    greet("ajay")
    
    return 0;
}

// function defination
void greet(string name){

cout << "Hello " << name;

}
    
    

create a new directory to work with

eg

HelloWorld/utls

add 2 files in this directory

1. the header file // eg greet.h or greet.hpp both works but greet.hpp is more common
2. the implemientaion file // eg greet.cpp

HelloWorld/utls/greet.cpp

#include <iostream> // you have to include this at the top

using namespace std;

// function defination
void greet(string name){

cout << "Hello " << name;

}

HelloWorld/utls/greet.hpp

#include <string> // we could #include <iostream> but it is not neccessary here so only using #include <string> where the string class is defined


// function decaleration (function prototype)
void greet(std::string name);  //now as we included #include <string> change string to std::string

now in our main file becomes like this

HelloWorld/main.hpp

#include <iostream>
#include "utils/greet.hpp"

using namespace std;

int main(){

greet("AJ")

return 0;

}

the above file still cause error on build time

if you include #include "utils/greet.hpp"in another (like we did in main.cpp) this will cause error, so wee need to tell to only include this once

go to HelloWorld/utls/greet.hpp and use another derective ifndef

#ifndef UTILS_GREET               // #ifndef the any constant(here we used UTILS_GREET)
#define UTILS_GREET                //if not defined , define it UTILS_GREET (both spelling should be exactly the same)

#include <string>

void greet(std::string name);

#endif

when the above lines run first it check for if not define, the run all the code inside(define it and all code) utils to we get to endif but when it runs again ,now the constant UTILS_GREET is defien so it will not run the code inside

to build from multiple files

g++ -o main.exe main.cpp utils/greet.cpp

namespace

utils/greet.hpp

#ifndef UTILS_GREET               // #ifndef the any constant(here we used UTILS_GREET)
#define UTILS_GREET                //if not defined , define it UTILS_GREET (both spelling should be exactly the same)

#include <string>
namespace messaging {

    void greet(std::string name);
}

#endif

utils/greet.cpp

#include <iostream>

using namespace std;

namespace messaging {
    void greet(string name){
        cout << "Hello " + name

        }
}

main.cpp

#include <iostream>
#include "utils/greet.hpp"

using namespace std;

int main(){
    messaging::greet("AJ")
    return 0;
}

another version

#include <iostream>
#include "utils/greet.hpp"

using namespace std;
using namespace messaging;


int main(){
    greet("AJ")
    greet("AJ")
    greet("AJ")
    greet("AJ")
    return 0;
}

another version

sometiem we may need to import only specific function only form a namespace

#include <iostream>
#include "utils/greet.hpp"

using namespace std;
using messaging::greet;


int main(){
    greet("AJ")
    greet("AJ")
    greet("AJ")
    greet("AJ")
    return 0;
}

if you only need cout, or any specific one

using std::cout;

using std::cout;
using std::cin;

using std::cout, std::cin;

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