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A fixed 32-bit data format for system time means that timestamps rolls over approximately every 136 years, with the first such occurrence on 7 February 2036.
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bit(3f) [bsd man page]

BIT(3F) 																   BIT(3F)

NAME
bit - and, or, xor, not, rshift, lshift bitwise functions SYNOPSIS
(intrinsic) function and (word1, word2) (intrinsic) function or (word1, word2) (intrinsic) function xor (word1, word2) (intrinsic) function not (word) (intrinsic) function rshift (word, nbits) (intrinsic) function lshift (word, nbits) DESCRIPTION
These bitwise functions are built into the compiler and return the data type of their argument(s). Their arguments must be integer or log- ical values. The bitwise combinatorial functions return the bitwise ``and'' (and), ``or'' (or), or ``exclusive or'' (xor) of two operands. Not returns the bitwise complement of its operand. Lshift, or rshift with a negative nbits, is a logical left shift with no end around carry. Rshift, or lshift with a negative nbits, is an arithmetic right shift with sign extension. No test is made for a reasonable value of nbits. These functions may be used to create a variety of general routines, as in the following statement function definitions: integer bitset, bitclr, getbit, word, bitnum bitset( word, bitnum ) = or(word,lshift(1,bitnum)) bitclr( word, bitnum ) = and(word,not(lshift(1,bitnum))) getbit( word, bitnum ) = and(rshift(word,bitnum),1) FILES
These functions are generated in-line by the f77 compiler. 4.2 Berkeley Distribution April 30, 1986 BIT(3F)

Check Out this Related Man Page

BITSTRING(3)						   BSD Library Functions Manual 					      BITSTRING(3)

NAME
bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set, bitstr_size, bit_test -- bit-string manipulation macros SYNOPSIS
#include <bitstring.h> bitstr_t * bit_alloc(int nbits); bit_decl(bitstr_t *name, int nbits); bit_clear(bitstr_t *name, int bit); bit_ffc(bitstr_t *name, int nbits, int *value); bit_ffs(bitstr_t *name, int nbits, int *value); bit_nclear(bitstr_t *name, int start, int stop); bit_nset(bitstr_t *name, int start, int stop); bit_set(bitstr_t *name, int bit); int bitstr_size(int nbits); int bit_test(bitstr_t *name, int bit); DESCRIPTION
These macros operate on strings of bits. The macro bit_alloc() returns a pointer of type ``bitstr_t *'' to sufficient space to store nbits bits, or NULL if no space is available. The macro bit_decl() allocates sufficient space to store nbits bits on the stack. The macro bitstr_size() returns the number of elements of type bitstr_t necessary to store nbits bits. This is useful for copying bit strings. The macros bit_clear() and bit_set() clear or set the zero-based numbered bit bit, in the bit string name. The bit_nset() and bit_nclear() macros set or clear the zero-based numbered bits from start to stop in the bit string name. The bit_test() macro evaluates to non-zero if the zero-based numbered bit bit of bit string name is set, and zero otherwise. The bit_ffs() macro stores in the location referenced by value the zero-based number of the first bit set in the array of nbits bits refer- enced by name. If no bits are set, the location referenced by value is set to -1. The macro bit_ffc() stores in the location referenced by value the zero-based number of the first bit not set in the array of nbits bits ref- erenced by name. If all bits are set, the location referenced by value is set to -1. The macros bit_clear(), bit_set() and bit_test() will evaluate the bit argument more than once, so avoid using pre- or post-, increment or decrement. The arguments to the other macros are evaluated only once and may safely have side effects. EXAMPLE
#include <limits.h> #include <bitstring.h> #define LPR_BUSY_BIT 0 #define LPR_FORMAT_BIT 1 #define LPR_DOWNLOAD_BIT 2 #define LPR_AVAILABLE_BIT 9 #define LPR_MAX_BITS 10 make_lpr_available() { bitstr_t bit_decl(bitlist, LPR_MAX_BITS); ... bit_nclear(bitlist, 0, LPR_MAX_BITS - 1); ... if (!bit_test(bitlist, LPR_BUSY_BIT)) { bit_clear(bitlist, LPR_FORMAT_BIT); bit_clear(bitlist, LPR_DOWNLOAD_BIT); bit_set(bitlist, LPR_AVAILABLE_BIT); } } SEE ALSO
malloc(3) HISTORY
The bitstring functions first appeared in 4.4BSD. 4th Berkeley Distribution July 19, 1993 4th Berkeley Distribution

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