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Questions tagged [bit]

The tag has no usage guidance.

54
votes
3answers
9k views

What is the name for storing / packing many boolean states into one number?

It's a sort of simple compression where you use one numeric variable to store many boolean / binary states, using doubling and the fact that every doubling number is 1 + the sum of all the previous ...
1
vote
2answers
54 views

Meaning of Using BitVectors to Model Integers to account for Overflow

I have just encountered this sentence: Depending on the context, we may prefer to model integers as bitvectors rather than mathematical integers, since the Int type does not model overflow. I am ...
1
vote
3answers
479 views

How can I query, increment & decrement arbitrary-length integers encoded into a bit-array?

I'm in the process of implementing a counting Bloom filter. This data structure is defined as a bit-array and a "width" parameter, W. The bit array stores unsigned integers, whose size is determined ...
2
votes
2answers
138 views

Why are CPUs' datapaths mutiple of 8?

Current and common processing units are 8, 16, 32, 64, 128, etc bit. Why are their datapath multiple of 8 ? Is this all linked to the fact that the industry has settled with a 8-bit byte ? The PDP-7 ...
11
votes
6answers
811 views

Is power-of-two bits per word “convenient”? If it is, why is that?

I find several sources claiming that power-of-two bits in a binary word (such as 8-bits per byte) is a "good thing" or "convenient". I find no source pointing out why. From What is the history of ...
2
votes
5answers
630 views

Why isn't byte | bit the only built in data type?

All languages I have seen so far have multiple builtin data types (int, double, float, char, long...). But if we look closely, they are just arbitrary arrays of bits, the only difference between them ...
20
votes
6answers
6k views

Advantages and disadvantages of using bit masks in database

Not so long ago I talked to my colleague and he was definitely against using bit masks because it is hard to understand all the values that are stored in the database. In my opinion it is not always a ...
2
votes
4answers
3k views

Byte addressable vs bit addressable

Why are most computers byte addressable instead of bit addressable? By B/b addressable I mean that processor can operate on level of single B/b. Bit addressable advantages: Booleans have size of ...
0
votes
3answers
559 views

Bits - Least-Significant/Lowest is 0th or 1st; zero or one indexed

Question Is there a rough consensus if the bitmask 0x01 is properly said to have the "zeroth" bit set, or the "first" bit set? If there isn't rough consensus that there's a generally right answer, ...
3
votes
2answers
1k views

Explanation to why Counting bits set, Brian Kernighan's way works

I found this link to count number of bits in a variable. I think it is pretty cool, but I can't figure out why it works. Can someone offer an explanation? Here is the code unsigned int v; // count ...
0
votes
1answer
4k views

What is the difference between size and length? [closed]

It seems that the terms size and length are used interchangeably to describe how many bits, bytes or octets some data occupies, i.e. a length field in a data header is said to indicate the size of the ...
3
votes
1answer
1k views

Endianness at bit level

I am learning the union and struct and I wrote the code below. What I do not understand is why the output is different when I change from a little endian to a big endian machine. My understanding is ...
-4
votes
3answers
1k views

Save flags in an int32 [closed]

Unity3d PlayerPrefs only allow saving certain types - string, float, and int32. Since int is composed of 32 bits, it should be able to store 32 flags or a bool[] of length 32. So far, I've thought ...
4
votes
3answers
1k views

Is a 'least significant bit' used anywhere practically today?

I'm working on a library that supports file reading, and right now I've always assumed that all the bytes are written in most significant bit first format. Is the least significant bit first format ...
4
votes
3answers
2k views

How does word size affect the amount of virtual address space available?

So, I should really know this stuff already, but I am starting to learn more about the lower levels of software development. I am currently reading Computer Systems: A Programmer's Perspective. by ...
11
votes
3answers
61k views

How are negative signed values stored?

I was watching this video on the maximum and minimum values of signed integers. Take an example of a positive signed value - 0000 0001 The first bit denotes that the number is positive and the last ...
0
votes
1answer
343 views

Understanding bitmap logic

I was going though this blog and it says You can represent a list of distinct integers no larger than N using exactly N bits: if the integer i appears in your list, you set the i th bit to true. ...
5
votes
1answer
2k views

Clearing the lowest set bit of a number

I can see in this tutorial on bit manipulation, under the heading "Extracting every last bit", that - Suppose we wish to find the lowest set bit of x (which is known to be non-zero). If we ...
3
votes
3answers
2k views

8 bit and 1 byte, is this a valid question to be asked?

I saw these question in our school's past paper, and I'm wondering if this is a valid question. How big is bool in C and C++? A) 1 bit B) 4 bit C) 8 bit D) 1 byte What is ...
2
votes
4answers
7k views

How to get from 1 byte to 2 bytes

We have 1 byte, which is 8 bits, which is 2^8. Now 2 bytes should be 2 * 1 byte, which is 2 * 2^8 = 2^9, but actually 2 bytes is 2^16. What am I missing here? It seems like 2 bytes isn't 2 * 1 byte, ...
1
vote
3answers
399 views

How do I tell a user that bps means bits per second or bytes per second?

I'm writing an application that deals with the network and the hard drive. For the network portion, the application measures in bits per second, while the disk portion measures in bytes per second. ...
42
votes
13answers
5k views

Is there an alternative to bits?

Is there an alternative to bits as the smallest unit of data? Something that won't be only 0 or 1, but actually hold many possible states in between? Wouldn't it be more natural to store floats like ...
81
votes
7answers
55k views

What is the history of why bytes are eight bits?

What where the historical forces at work, the tradeoffs to make, in deciding to use groups of eight bits as the fundamental unit ? There were machines, once upon a time, using other word sizes, ...