Comments can be used to explain C++ code, and to make it more readable. It can also be used to prevent execution when testing alternative code. Comments can be singled-lined or multi-lined.
Example
// This is a comment
cout << "Hello World!";
This example uses a single-line comment at the end of a line of code:
Example
cout << "Hello World!"; // This is a comment
Multi-line comments start with /* and ends with */.
Any text between /* and */ will be ignored by the compiler:
Example
/* The code below will print the words Hello World!
to the screen, and it is amazing */
cout << "Hello World!";
Variables are containers for storing data values.
In C++, there are different types of variables (defined with different keywords), for example:
To create a variable, specify the type and assign it a value:
Syntax
type variableName = value;
Where type is one of C++ types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.
To create a variable that should store a number, look at the following example:
Example
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:
Example
int myNum;
myNum = 15;
cout << myNum;
Note that if you assign a new value to an existing variable, it will overwrite the previous value:
Example
int myNum = 15; // myNum is 15
myNum = 10; // Now myNum is 10
cout << myNum; // Outputs 10
A demonstration of other data types:
Example
int myNum = 5; // Integer (whole number without decimals)
double myFloatNum = 5.99; // Floating point number (with decimals)
char myLetter = 'D'; // Character
string myText = "Hello"; // String (text)
bool myBoolean = true; // Boolean (true or false)
The cout object is used together with the << operator to display variables.
To combine both text and a variable, separate them with the << operator:
Example
int myAge = 35;
cout << "I am " << myAge << " years old.";
To add a variable to another variable, you can use the + operator:
Example
int x = 5;
int y = 6;
int sum = x + y;
cout << sum;
To declare more than one variable of the same type, use a comma-separated list:
Example
int x = 5, y = 6, z = 50;
cout << x + y + z;
You can also assign the same value to multiple variables in one line:
Example
int x, y, z;
x = y = z = 50;
cout << x + y + z;
Note: It is recommended to use descriptive names in order to create understandable and maintainable code:
Example
// Good
int minutesPerHour = 60;
// OK, but not so easy to understand what m actually is
int m = 60;
The general rules for naming variables are:
When you do not want others (or yourself) to override existing variable values, use the const keyword (this will declare the variable as "constant", which means unchangeable and read-only):
Example
const int myNum = 15; // myNum will always be 15
myNum = 10; // error: assignment of read-only variable 'myNum'
You should always declare the variable as constant when you have values that are unlikely to change:
Example
15 videos|20 docs|13 tests
|
|
Explore Courses for Class 10 exam
|