[ETC] 0xff handling

• 0xff is the hexadecimal number FF which has a integer value of 255.
• 0xff means “the hexadecimal number ff “ - in other words, the integer 255 , which has the binary representation 00000000000000000000000011111111 (when using under 32-bit integers). The & operator performs a bitwise AND operation.
• 메모리는 모든데이터를 1과0으로만 구성한 2진수로 저장
• 8개의 비트를 모아서 1Byte -> 2의 8승이며 표시 가능한 숫자의 갯수는 256가지
• 16진수표현 중 가장 큰 수인 F는 비트로 1111을 뜻하고 10진수로는 15
• 즉 8개의 비트 1111은 16진수 값으로 F에 해당하며 16진수를 표현할때는 앞에 ‘0x’를 붙임

byte a = ( b >>  8) & 0xff; // b is an integer

• The & operator performs a bitwise AND operation. a & b will give you an integer with a bit pattern that has a 0 in all positions where b has a 0, while in all positions where b has a 1, the corresponding bit value froma is used (this also goes the other way around). For example, the bitwise AND of 10110111 and00001101 is 00000101.

• In a nutshell, “& 0xff” effectively masks the variable so it leaves only the value in the last 8 bits, and ignores all the rest of the bits.

• It’s seen most in cases like when trying to transform color values from a special format to standard RGB values (which is 8 bits long).

• INT_MAX 2147483647
• UINT_MAX 4294967295 (0xffffffff)
• UCHAR_MAX 255 (0xff)
• Limits on Integer Constants