2.6. Keywords

A few sections ago, I said that you can make up any name you want for your variables, but that’s not quite true. There are certain words that are reserved in C++ because they are used by the compiler to parse the structure of your program, and if you use them as variable names, it will get confused. These words, called keywords, include int, char, void, endl and many more.

A list of C++ keywords is availiable publically on cppreference. You can take a look for yourself by pasting the following link into your browser.

https://en.cppreference.com/w/cpp/keyword

Rather than memorize the list, I would suggest that you take advantage of a feature provided in many development environments: code highlighting. As you type, different parts of your program should appear in different colors. For example, keywords might be blue, strings red, and other code black.

Warning

If you type a variable name and it turns blue, watch out! You might get some strange behavior from the compiler.

Note

Case matters! You can name a string variable String without an issue because C++ does not consider String to be the same as keyword string. Also, a anything written in quotes, for example "string" is not considered a keyword in C++, even if it is spelt the same.

Q-1: Words that are reserved in C++ because they are used by the compiler to parse the structure of your program are called .

Q-2: Multiple Response: Which of the following are keywords or will otherwise generate some error from the compiler if used as a variable name?

• integer
• integer is not a keyword, but int is.
• cout
• cout cannot be used as a variable name!
• variable
• variable is fair game to use to name a variable.
• string
• string cannot be used as a variable name.
• char
• char is a keyword and cannot be used as a variable name.

Q-3: Click on all keywords.Try again!

int main() {
    double x = 1.0;
    int y = x + 5;
    bool Bool;
    string s = "void";
    if (y > x) {
       Bool = true;
    }
    cout << Bool << endl;
}

Fix the code below so that it runs without errors. Hint: you might need to change the names of some variables.

#include <iostream> using namespace std; int main () { int friend = 4; int enemy = friend * (-1); cout << "enemy = " << enemy << endl; // Do not modify anything below. return 0; }

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