C/Macro Preprocessor/Macro Basic
Check if a macro has been defined
#include <stdio.h>
#define VAL 40;
#undef VAL
#define VAL 40
main()
{
printf ("%d\n", VAL);
}
Macro in different file
//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);
}
Use macro in calculation
#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);
}