Comments

Comments are for human readers. They let you explain intent, mark a tricky detail, or leave a short note near a piece of code without changing what the compiler does.

That makes comments a small topic, but an important one: good comments can make the difference between code that merely works and code that is easy to revisit later.

For each short example below, save the file as concepts.scpp, then build and run it like this:

scpp concepts.scpp -o concepts
./concepts

Line comments

The most common form is a line comment starting with //.

import std;

int main() {
    // This comment is for people, not for the compiler.
    int answer = 40 + 2;

    std::println("answer = {}", answer);
    return 0;
}

Output:

answer = 42

Everything after // on that line is ignored by the compiler.

Block comments

When one short line is not enough, use a block comment.

import std;

int main() {
    /* A block comment can cover more than one line
       when one short note is not enough. */
    int total = 20 + 22;

    std::println("total = {}", total);
    return 0;
}

Output:

total = 42

Block comments are useful for a slightly longer explanation that still belongs right next to the code it describes.

Short comments beside a statement

Sometimes the clearest note is a tiny reminder at the end of the line it explains.

import std;

int main() {
    int score = 7; // starting score for this round
    score = score + 5;

    std::println("score = {}", score);
    return 0;
}

Output:

score = 12

This style works best when the comment is brief. If the explanation gets long, move it above the statement instead.

A practical rule

Good comments explain why, not just what. If code already says exactly what it is doing, repeating that in prose usually adds noise. Save comments for:

• intent that is not obvious from the code alone;
• assumptions a reader should know;
• quick orientation in a longer function or module.

The next section returns to program behavior and control flow: choosing between paths with if and repeating work with while.

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