To be or not to be, that is the question
This chapter discusses bit-oriented operations. A bit is the smallest unit of information. Normally, it is represented by the values 1 and 0. (Other representations include on/off, true/false, and yes/no.) Bit manipulations are used to control the machine at the lowest level. They allow the programmer to get under the hood of the machine. Many higher-level programs will never need bit operations. Low-level coding, like writing device drivers or pixel-level graphic programming, requires bit operations.
Eight bits together form a byte, represented by the C data type char.
A byte might contain the following bits:
This bit structure can also be written as the hexadecimal number 0x64. (C uses the prefix “0x” to indicate a hexadecimal (base 16) number.) Hexadecimal is convenient for representing binary data because each hexadecimal digit represents 4 binary bits. Table 11-1 gives the hexadecimal-to-binary conversion:
So the hexadecimal number 0xAF represents the binary number 10101111.
printf format for
%x; for octal the
int number = 0xAF; printf("Number is %x %d %o\n", number, number, number);
af 175 257
Many novice programmers get a number confused with its representation ...