The void Data Type in C Programming

The void Data Type

You may notice that the void word has been added into the C program in Listing 2.2. void is a keyword for a data type in C. When a void is placed prior to a function name, it indicates that the function does not return a value.

As you have learned, the exit() function does not return any values, but, by default, the main() function does. Therefore, as shown in line 5 of Listing 2.2, void is used to modify the returning data type of main() and to make the main() function not return any value. (You'll learn more about data types in C in Hours 4, "Data Types and Names in C," and 18, "More Data Types and Functions.")

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The #define and #undef Directives

The #define and #undef Directives

The #define directive is the most common preprocessor directive, which tells the preprocessor to replace every occurrence of a particular character string (that is, a macro name) with a specified value (that is, a macro body).

The C Preprocessor Versus the Compiler

The C Preprocessor Versus the Compiler

One important thing you need to remember is that the C preprocessor is not part of the C compiler.

What Is the C Preprocessor?

If there is a constant appearing in several places in your program, it's a good idea to associate a symbolic name to the constant, and then use the symbolic name to replace the constant throughout the program. There are two advantages to doing so. First, your program will be more readable.

Exercises : Answer the following Question

To help solidify your understanding of this hour's lesson, you are encouraged to answer the quiz questions and finish the exercises provided in the Workshop before you move to the next lesson.

Question and Answer

Q Why is random access to a disk file necessary?