In C++, you could use the #define preprocessor directive in three ways:
- Define a symbol and then later check to see if the symbol exists
- Define a symbol, giving it a particular value that you can later check
- Define a symbol and give it a definition (a macro)
- Provide parameters as part of the symbol’s definition
In C++, the #define directive assigns some arbitrary text to a symbol and the preprocessor substitutes the text for the symbol, wherever the symbol appears in your code.
As an example, you could use C++ to create a macro by defining the symbol MAX as follows:
1
| #define MAX(a,b) (a>b)?a:b |
The #define directive in C# is much more limited. Of the four uses for #define listed above, only the first one is supported in C#. You use the #define directive to define a symbol that is either present or not present.