You may have noticed while using cout (console-output) in C++, we have 2 common options to move the cursor to the newline(ie \n and endl). Both \n and endl are used to move the cursor to the next line, but they are not the same in terms of performance and behavior.

#include <iostream>
using namespace std;

int main() {
    // Using \n
    cout << "Hello with \\n" << '\n';
    // Using endl
    cout << "Hello with endl" << endl;
    return 0;
}

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Prerequisites

Concept of Buffer

In most programming languages, output is not sent directly to the screen but first stored in a buffer (a temporary memory area). This buffering improves performance because writing to the screen or an output device is much slower than writing to memory.

Concept of Flushing

Flushing ensures that the output is displayed immediately by forcing the program to send the buffered content to the output device right away. This is useful in situations where real-time updates are required, such as showing progress indicators.

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Working

Working of \n

1. \n is simply a newline character.

2. When used in the output stream, it moves the cursor to the next line but does not flush the buffer.

3. The text remains in the output buffer and will only be displayed when:

   1. The buffer is full,

   2. The program ends, or

   3. A flush operation occurs manually/implicitly.

4. Since it avoids unnecessary flushing, \n is faster and preferred in competitive programming and performance-critical tasks

Working of endl

1. endl also inserts a newline character, just like \n.

2. But in addition, it forces the output buffer to flush immediately, sending all buffered content to the output device.

3. This ensures the output appears instantly, which is useful for debugging, logging, or real-time updates.

4. However, frequent flushing makes it slower compared to \n.

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TLDR

Use \n for speed, use endl when you need output immediately.

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