Bit Manipulation in The C Programming Language
C has direct support for bitwise operations that can be used for bit manipulation. In the following examples, n is the index of the bit to be manipulated within the variable bit_fld, which is an unsigned char being used as a bit field. Bit indexing begins at 0, not 1. Bit 0 is the least significant bit.
- Set a bit
- Clear a bit
- Toggle a bit
- Test a bit
When using an array of bytes to represent set of bits, i.e., a bit array or bitset, the index of the byte in the array associated with a bit n can be calculated using division:
where n is the index of the given bit and CHAR_BIT gives the number of bits in a C char.
The index of the bit within the byte indexed by the above can be calculated via a modulo operation:
n % CHAR_BIT(Note: unsigned char is typically used in C to represent a byte and CHAR_BIT is most often 8 on modern processors. % is the C modulo operator.)
Read more about this topic: Bit Manipulation
Famous quotes containing the words bit, manipulation, programming and/or language:
“With a little bit of luck, you’ll never work!”
—Alan Jay Lerner (1918–1986)
“The basic tool for the manipulation of reality is the manipulation of words. If you can control the meaning of words, you can control the people who must use the words.”
—Philip K. Dick (1928–1982)
“If there is a price to pay for the privilege of spending the early years of child rearing in the driver’s seat, it is our reluctance, our inability, to tolerate being demoted to the backseat. Spurred by our success in programming our children during the preschool years, we may find it difficult to forgo in later states the level of control that once afforded us so much satisfaction.”
—Melinda M. Marshall (20th century)
“the language obscene
An engine, an engine
Chuffing me off like a Jew.”
—Sylvia Plath (1932–1963)