A macro is a segment of code which is replaced by the value of macro. Macro is defined by #define directive. There are two types of macros:
- Object-like Macros
- Function-like Macros
Object-like Macros
The object-like macro is an identifier that is replaced by value. It is widely used to represent numeric constants. For example:
- #define PI 3.14
Here, PI is the macro name which will be replaced by the value 3.14.
Function-like Macros
The function-like macro looks like function call. For example:
- #define MIN(a,b) ((a)<(b)?(a):(b))
Here, MIN is the macro name.
Visit #define to see the full example of object-like and function-like macros.
C Predefined Macros
ANSI C defines many predefined macros that can be used in c program.
| No. | Macro | Description |
|---|---|---|
| 1 | _DATE_ | represents current date in “MMM DD YYYY” format. |
| 2 | _TIME_ | represents current time in “HH:MM:SS” format. |
| 3 | _FILE_ | represents current file name. |
| 4 | _LINE_ | represents current line number. |
| 5 | _STDC_ | It is defined as 1 when compiler complies with the ANSI standard. |
C predefined macros example
File: simple.c
- #include <stdio.h>
- main() {
- printf(“File :%s\n”, __FILE__ );
- printf(“Date :%s\n”, __DATE__ );
- printf(“Time :%s\n”, __TIME__ );
- printf(“Line :%d\n”, __LINE__ );
- printf(“STDC :%d\n”, __STDC__ );
- }
Output:
File :simple.c Date :Dec 6 2015 Time :12:28:46 Line :6 STDC :1
