单片机入门：使用do while循环控制P1端口输出

#include <reg51.h>

main() { char a;

do { a = P1; a = a & 0x03;

if (a == 0) {
  P1 = 0x83;
} else if (a == 1) {
  P1 = 0x43;
} else if (a == 2) {
  P1 = 0x23;
} else {
  P1 = 0x13;
}

} while (1); }