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C++ Basics
Introduction to
The
#include <iostream>
using namespace std;
int main() {
cout << "Hello, World!";
return 0;
}
Console Output:
Hello, World!
Using cin for Input
Reading User Input with cin
The cin object is used to accept input from the user. It reads data from the standard input stream.
#include <iostream>
using namespace std;
int main() {
int age;
cout << "Enter your age: ";
cin >> age;
cout << "You are " << age << " years old.";
return 0;
}
Console Output:
Enter your age: 25
You are 25 years old.
Using endl for New Line
Creating New Lines with endl
The endl manipulator is used to insert a newline character and flush the output buffer.
#include <iostream>
using namespace std;
int main() {
cout << "Hello," << endl;
cout << "World!";
return 0;
}
Console Output:
Hello,
World!
Formatted Output with setw
Aligning Output with setw
The setw manipulator is used to set the width of the output field.
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
cout << setw(10) << "Hello" << setw(10) << "World" << endl;
return 0;
}
Console Output:
Hello World
Using getline for String Input
Reading Full Lines with getline
The getline function is used to read a line of text, including spaces, from an input stream.
#include <iostream>
#include <string>
using namespace std;
int main() {
string name;
cout << "Enter your full name: ";
getline(cin, name);
cout << "Hello, " << name << "!";
return 0;
}
Console Output:
Enter your full name: John Doe
Hello, John Doe!
Using cerr for Error Messages
Outputting Errors with cerr
The cerr object is used for outputting error messages. It is unbuffered and outputs immediately.
#include <iostream>
using namespace std;
int main() {
cerr << "Error: Something went wrong!" << endl;
return 0;
}
Console Output:
Error: Something went wrong!
Using clog for Logging
Logging Information with clog
The clog object is used for logging information. It is buffered, meaning it might not output immediately.
#include <iostream>
using namespace std;
int main() {
clog << "Log: Program started successfully." << endl;
return 0;
}
Console Output:
Log: Program started successfully.
Chaining Input and Output
Combining Multiple Operations
In C++, you can chain multiple input and output operations using the << and >> operators.
#include <iostream>
using namespace std;
int main() {
int a, b;
cout << "Enter two numbers: ";
cin >> a >> b;
cout << "Sum: " << a + b << endl;
return 0;
}
Console Output:
Enter two numbers: 3 5
Sum: 8
Manipulating Output with setprecision
Setting Decimal Precision
The setprecision manipulator is used to control the number of digits displayed after the decimal point for floating-point numbers.
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
double pi = 3.14159;
cout << setprecision(3) << pi << endl;
return 0;
}
Console Output:
3.14
Using ios::fixed for Fixed Point Notation
Displaying Fixed Point Numbers
The ios::fixed is used to display floating-point numbers in fixed-point notation.
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
double num = 123.456;
cout << fixed << setprecision(2) << num << endl;
return 0;
}
Console Output:
123.46
