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1.6 — Whitespace and basic formatting

Whitespace is a term that refers to characters that are used for formatting purposes. In C++, this refers primarily to spaces, tabs, and (sometimes) newlines. The C++ compiler generally ignores whitespace, with a few minor exceptions.

Consequently, the following statements all do the exact same thing:

Even the last statement with the newline in it compiles just fine.

The following functions all do the same thing:

One exception where the C++ compiler does pays attention to whitespace is inside quoted text, such as "Hello world!".

"Hello world!"

is different than

"Hello     world!"

and each prints out exactly as you’d expect.

Newlines are not allowed in quoted text:

Another exception where the C++ compiler pays attention to whitespace is with // comments. Single-line comments only last to the end of the line. Thus doing something like this will get you in trouble:

Basic formatting

Unlike some other languages, C++ does not enforce any kind of formatting restrictions on the programmer (remember, trust the programmer!). Many different methods of formatting C++ programs have been developed throughout the years, and you will find disagreement on which ones are best. Our basic rule of thumb is that the best styles are the ones that produce the most readable code, and provide the most consistency.

Here are our recommendations for basic formatting:

1) Your tabs should be set to 4 spaces (most IDEs have a setting where you can configure this). Some IDEs default to 3 spaces, which is fine too.

The reason to use spaces instead of tab characters is so that if you open your code in another viewer, it’ll retain the correct indentation.

2) The braces that tell where a function begins and ends should be aligned with the function name, and be on their own lines:

Although some coders prefer other styles, this one is the most readable and least error prone since your brace pairs should always be indented at the same level. If you get a compiler error due to a brace mismatch, it’s very easy to see where.

3) Each statement within braces should start one tab in from the opening brace of the function it belongs to. For example:

4) Lines should not be too long. Typically, 72, 78, or 80 characters is the maximum length a line should be. If a line is going to be longer, it should be broken (at a reasonable spot) into multiple lines. This can be done by indenting each subsequent line with an extra tab, or if the lines are similar, by aligning it with the line above (whichever is easier to read).

5) If a long line that is broken into pieces is broken with an operator (eg. << or +), the operator should be placed at the end of the line, not the start of the next line:

Not

This makes it more obvious from looking at the first line that the next line is going to be a continuation.

6) Use whitespace to make your code easier to read.

Harder to read:

Easier to read:

Harder to read:

Easier to read:

Harder to read:

Easier to read:

We will follow these conventions throughout this tutorial, and they will become second nature to you. As we introduce new topics to you, we will introduce new style recommendations to go with those features.

Ultimately, C++ gives you the power to choose whichever style you are most comfortable with, or think is best. However, we highly recommend you utilize the same style that we use for our examples. It has been battle tested by thousands of programmers over billions of lines of code, and is optimized for success.

1.7 -- Forward declarations and definitions [1]
Index [2]
1.5 -- A first look at operators [3]