C语言预处理指令define

/* preproc.c -- simple preprocessor examples */
#include <stdio.h>
#define TWO 2        /* you can use comments if you like   */
#define OW "Consistency is the last refuge of the unimagina\
tive. - Oscar Wilde" /* a backslash continues a definition */
/* to the next line                   */
#define FOUR  TWO*TWO
#define PX printf("X is %d.\n", x)
#define FMT  "X is %d.\n"

int main(void)
{
    int x = TWO;

    PX;
    x = FOUR;
    printf(FMT, x);
    printf("%s\n", OW);
    printf("TWO: OW\n");

    return 0;
}