In C++, cout is an object of the ostream class that is used to display output to the standard output device, usually the monitor. It is associated with the standard C output stream stdout. The insertion operator (<<) is used with cout to insert data into the output stream.
Let's take a look at an example:
C++
#include <iostream>
using namespace std;
int main() {
// Print standard output
// on the screen
cout << "Welcome to GFG";
return 0;
}
Syntax of cout
cout << var_name;
Here,
- <<: It is the insertion operator used to insert data into cout.
- var_name: It represents the variable or literal whose value you want to display.
Examples of cout in C++
The below programs demonstrate how to use the cout for output purposes in C++.
Print Hello World
C++
#include <iostream>
using namespace std;
int main() {
// Printing hello world using cout
cout << "Hello, World!";
return 0;
}
Displaying Multiple Variables
C++
#include <iostream>
using namespace std;
int main() {
int n = 42;
string s = "The answer is ";
// Printing both n and s
cout << s << n;
return 0;
}
cout Member Functions in C++
Below is a list of some commonly used member functions of cout in C++:
| Member Function | Description |
|---|
| cout.put(char) | Writes a single character to the output stream. |
| cout.write(char*, int) | Writes a block of characters from the array to the output stream. |
| cout.precision(int) | Sets the decimal precision for displaying floating-point numbers. |
| cout.setf(ios::fmtflags) | Sets the format flags for the stream. |
| cout.width(int) | Sets the minimum field width for the next output. |
| cout.fill(char) | Sets the fill character for padding the field. |
Below is the implementation of the member functions of the cout.write() and cout.put():
C++
#include <iostream>
using namespace std;
int main() {
char s[] = "Welcome at GFG";
char c = 'e';
// Print first 6 characters
cout.write(s, 6);
// Print the character c
cout.put(c);
return 0;
}
Below is the C++ program to illustrate the use of cout.precision():
C++
#include <iostream>
using namespace std;
int main() {
double pi = 3.14159783;
// Set precision to 5
cout.precision(5);
cout << pi << endl;
// Set precision to 7
cout.precision(7);
cout << pi << endl;
return 0;
}
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