C/Macro Preprocessor/Macro Basic
Check if a macro has been defined
<source lang="cpp">
- include <stdio.h>
- define VAL 40;
- undef VAL
- define VAL 40
main() {
printf ("%d\n", VAL);
}
</source>
Macro in different file
<source lang="cpp"> //file1.h
- define USD 1
//file2.h
- define UKP 1
//file3
- include <stdio.h>
- include <file1.h>
- ifdef USD
#define currency_rate 46
- endif
- ifdef UKP
#define currency_rate 100
- endif
main() {
int rs; rs = 10 * currency_rate; printf ("%d\n", rs);
}
</source>
Use macro in calculation
<source lang="cpp">
- include <stdio.h>
- define Var1 7
- define Var2 5
- define Var3 Var1 + Var2
int main() {
printf("The square of all the parts is %d\n", Var3 * Var3); return (0);
}
</source>