11. Counter, Arithmetic Mean and Division by Zero

Keywords Are Reserved

We have stumbled upon many words that have special meaning in the C++ language, such as double, int, for, if, else, using, namespace. You can probably notice that your source code editor is displaying those words in a different color. These words are recognized by the C++ compiler as having a preset and special meaning in the language, which is why they are called the keywords. It is not possible to introduce a name that would be the same as a keyword. It is thus said that the keywords are reserved in the C++ language.

Other words that you have encountered, like cin, cout, endl, main, vector are not keywords. These words are names, more precisely identifiers, created by other features of the language.