struct A
{
char t:4;
char k:4;
unsigned short i:8;
unsigned long m;
}
sizeof(A)= （不考虑边界对齐）
struct CELL // Declare CELL bit field
unsigned character : 8; // 00000000
unsigned foreground : 3; // 00000 00000000
unsigned intensity : 1; // 0000 000 00000000
unsigned background : 3; // 0 0000 00000000
unsigned blink : 1; // 0000000 00000000
} screen[25][80]; // Array of bit fields