9e5d2baac1
* ADD "Undefining Macro" we can undefine macro whenever we want in code by adding #undefine * fix: markdown title format * fix: minor grammar corrections Capitalise first word and remove extra full stops
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| Macros in C |
Macros in C
A macro is a piece of code with a given name. When the name is used, it is replaced by the content of the macro.
Defining macros
The #define keyword is used to define new macros. It's followed by a name and a content. By convention, macro names are written in uppercase.
#define PI 3.14
If you use the macro this way:
printf("Value of PI: %d", PI);
Is the same as write this:
printf("Value of PI: %d", 3.14);
Undefining Macros
After defining macros you can also undefine them at any point. just Type
#undefine PI
This is used to use macros only for specific lines of code and again undefine it.
Types of macros
There are two type of macros. The Object-like macros, showed above, and the Function-like macros.
Function-like Macros
Function-like uses the same #define keyword. The difference is that you use a pair o parentheses after the function name.
#define hello_world() printf("Hello World!")
So calling:
hello_world()
You get:
printf("Hello World!");
You can set parameters too:
#define hello(X) printf("Hello " X "!")
Now calling:
hello("World");
You get the equivallent of:
printf("Hello World!");
More Information:
GCC Online Documentation: Macros