C++ is a general-purpose programming language created by Bjarne Stroustrup as an extention of the C programming language. The language has expanded significantly over time, and modern C++ now has object-oriented, generic, and functional features in addition to facilities for low-level memory manupulation.
C++ is a must for students and working professionals to become a great Software Engineer. The following are the reasons why one should learn C++:
#include <iostream>
using namespace std;
int main() {
cout << "Hello World!";
return 0;
}
Variables are containers for storing data values. in C++, there are different types of variables, for example:
To create a variable, you must specify the type and assign it a value. Syntax is as follows:
type variable = value;
Following are few examples of declaring a variable:
Create a variable called myNum of type int and assign it the value 15:
int myNum = 15;
cout << myNum;
You can also declare a variable without assigning the value, and assign the value later:
int myNum;
myNum = 15;
cout << myNum;
A Data Type specifies the size and type of information the variable will store. The example is as follows:
int myNum = 5;
float myFloatNum = 5.99;
double myDouble = 9.98;
char myLetter = 'D';
string myText = "Hello";
Operators are used to perform operation on variables and values.
In the example below, we use the + operator to add together two values:
int x = 100 + 50;
C++ divides the operators into the following groups:
C++ supports the usual logical conditions from mathematics:
You can use these conditions to perform different actions of different decisions.
C++ has the following conditional statements:
if(20 < 18) {
cout << "20 is greater than 18";
}
In the example above we use two variables x and y, to test whether x is greater than y. As x is 20 and y is 18, and we know that 20 is greater han 18, we print to the screen that "x is greater than y".
int time = 20;
if (time < 18) {
cout << "Good day.";
} else {
cout << "Good evening.";
}
In the example above, time (20) is greater than 18, so the condition is false. Because of this, we move on to the else condition and print to the screen "Good evening.". If the time was less than 18, the program would print "Good day".
int time = 22;
if (time < 10) {
cout << "Good morning.";
} else if (time < 20) {
cout << "Good day.";
} else {
cout << "Good evening.";
}
In the example above, time (22) is greater than 10, so the first condition is false. The next condition, in the else if statement, is also false, so we move on to the else condition since condition1 and condition2 is both false - and print to the screen "Good evening".
Use the switch statement to select one of many code blocks to be executed.
The example below uses the weekday number to calculate the weekday name:
int day = 4;
switch (day) {
case 1:
cout << "monday";
break;
case 2:
cout << "tuesday";
break;
case 3:
cout << "wednesday";
break;
case 4:
cout << "thursday";
break;
case 5:
cout << "friday";
break;
case 6:
cout << "saturday";
break;
case 7:
cout << "sunday";
}
This is how it works:
Arrays are used to store multiple values in a single variable, instead of declaring seperate variables for each value.
To declare an array, define the variable type, specify the name of the array followed by square brackets and specify the number of elements it should store:
string cars[4] = {"Volvo", "BMW"};
You can access an array element by referring to the index number.
This statement accesses the value of the first element in cars:
string cars[4] = {"Volvo", "BMW"};
cout << cars[0];
A function is a block of code which only runs when it is called.
You can pass data, known as parameters, into a function.
Functions are used to perform certain actions, and they are important for reusing code: Define the code once, and use it many times.
C++ provides some pre-defined functions, such as main(), which is used to execute code. But you can also create your own functions to perform certain actions. To create (often referred to as declare) a function, specify the name of the function, followed by parentheses ():
void myFunction() {
// code to be executed
}
A C++ funtion consists of two parts:
void myFunction() { // declaration
// the body of the function (definition)
}
OOP stands for Object-Oriented Programming.
Procedural programming is about writing procedures or functions that perform operations on the data, while object-oriented programming is about creating objects that contain both data and functions.
Object-oriented programming has several advantages over procedural programming:
A class is a user-defined data type that we can use in our program, and it works as an object constructor, or a "blueprint" for creating objects.
To create a class, use the class keyword:
class MyClass {
public:
int myNum;
string myString;
}
In C++, an object is created from a class. We have already created the class named MyClass, so now we can use this to create objects.
To create an object of MyClass, specify the class name, followed by the object name. To access the class attributes (myNum and myString), use the dot syntax (.) on the object:
class MyClass {
public:
int myNum;
string myString;
int main() {
MyClass my
myObj.myNum = 15;
myObj.myString = "some text";
cout << myObj.myNum << "\n";
cout << myObj.myString;
return 0;
}