Generally speaking, for boolean or bit data types, you would use 0 or 1 like so: UPDATE tbl SET bitCol = 1 WHERE bitCol = 0 See also: Which MySQL data type to use for storing boolean values How do you create a yes/no boolean field in SQL server?
The number 0177 is an octal number representing the binary pattern below: 0000000001111111 When you AND it using the bitwise operation &, the result keeps the bits of the original only in the bits that are set to 1 in the “mask”; all other bits become zero. This is because “AND” follows this rule: X … Read more
SELECT * FROM table WHERE active = (1)
Try with this script, maybe will be useful: SELECT CAST(‘TRUE’ as bit) — RETURN 1 SELECT CAST(‘FALSE’ as bit) –RETURN 0 Anyway I always would use a value of 1 or 0 (not TRUE or FALSE). Following your example, the update script would be: Update Table Set BitField=CAST(‘TRUE’ as bit) Where ID=1
use limits.h CHAR_BIT http://www.cplusplus.com/reference/clibrary/climits/ also, when you want to use exactly a given size, use stdint.h
The classic approach of checking whether a bit is set, is to use binary “and” operator, i.e. x = 10 # 1010 in binary if x & 0b10: # explicitly: x & 0b0010 != 0 print(‘First bit is set’) To check, whether n^th bit is set, use the power of two, or better bit shifting … Read more
Since you mention C as well as C++, I’ll assume that a C++-oriented solution like boost::dynamic_bitset might not be applicable, and talk about a low-level C implementation instead. Note that if something like boost::dynamic_bitset works for you, or there’s a pre-existing C library you can find, then using them can be better than rolling your … Read more
The problem with bit fields is that the C standard does not dictate that the order in which they are defined is the same as the order that they are implemented. So you may not be setting the bits you think you are. Section 6.7.2.1p11 of the C standard states: An implementation may allocate any … Read more
Well, the answer is pretty simple. If you have an int value: int log2(int value) { return Integer.SIZE – Integer.numberOfLeadingZeros(value); } The same exists for Long… [Edit] If shaving milliseconds is an issue here, Integer.numberOfLeadingZeros(int) is reasonably efficient, but still does 15 operations… Expanding a reasonable amount of memory (300 bytes, static) you could shave … Read more
Well, I did dig up this paper, which claims that your RAM will get bit alterations from “Atmospheric Neutrons” (aka: Cosmic Rays) at a rate of about 1.3*10^-12 /bit/hour. An article by Berke Durak uses that to calculate that your probablilty of having at least one bit error in 4 gigabytes of memory at sea … Read more