STRUCT 키워드에서 :1 사용법

here is a little feature that allows you to save a little space.

main()   { struct Flags {   unsigned int Online :1; unsigned int Mounted :1; } struct Flags TapeInfo; TapeInfo.Online = 1; TapeInfo.Mounted = 0; }

The :1 tells the compiler that only 1 byte is required for Online and Mounted. There are a few points to note about this though.

• You may expect the compiler to reserve 2 bytes for the structure, it actually reserves one word (usually 4 bytes) as this is the smallest unit that can be reserved, the remaining 2 bytes are unavailable. This is still better than the 2 words that wold normally get reserved.
• You can put any number into the variable, if the number is too large to fit, the high order bits are lost without warning.
• Only signed int, unsigned int, int support this syntax.

출처 : http://www.space.unibe.ch/comp_doc/c_manual/C/SYNTAX/struct.html