{"id":7248,"date":"2025-11-22T00:01:07","date_gmt":"2025-11-22T08:01:07","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=7248"},"modified":"2025-11-29T11:46:26","modified_gmt":"2025-11-29T19:46:26","slug":"constantly-complaining","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=7248","title":{"rendered":"Constantly Complaining"},"content":{"rendered":"

The C language has an issue with constants. As far as I can tell, three different ways are at your disposal to express a constant: constant expressions, literal constants, and constant types. More variety may be available, which adds to the confusion.
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\nConstant Expressions.<\/strong> Also (and inconsistently) called symbolic constants<\/em>, these are created by using the precompiler #define<\/code> directive. For example:<\/p>\n

#define COUNT 30<\/code><\/p>\n

Traditionally, these constants are created in all caps, as shown with COUNT<\/code> above. What the precompiler does is to replace all instances of COUNT<\/code> in the source code file with the value or expression specified. This approach truly makes the expression constant, in that once the word is transformed into its assigned value the program cannot alter the value (or expression).<\/p>\n

I prefer use #define<\/code> to set constants in my code. Though it’s not a requirement to make it all caps, doing so makes it easier for me to locate them. Writing these constants in all caps is also the tradition for symbolic constants defined in the various header files, such as NULL<\/code>, FILE<\/code>, and so on.<\/p>\n

In a way, the constant expression is the true constant qualifier in C — and it’s not even part of the language.<\/p>\n

Literal Constants.<\/strong> A literal constant is any value you set directly into the code. Literals cannot be changed. Hence, they’re constant. But they’re also one-shot deals: If you need to repeat a value in the code, you must type it again. If you need to edit the value, you must hunt down all instances and change the value consistently. Doing so is a pain.<\/p>\n

Another problem with literal constants is that they occasionally become “magic numbers<\/a>,” which lack an explanation or reference as to their underlying purpose. (Click the link for an example.)<\/p>\n

Suffixes can be applied to some literal constants to confirm their values. These characters include:<\/p>\n