All Questions
Tagged with bitwise-operators c
11 questions
2
votes
2
answers
250
views
Are bitwise operators in C used both for bit operations and for operations for integer or some C types?
In C,
Bitwise logical operators &, |, ^ is used for selecting bits in a word.
Bitwise shifting operators >> and << can be used for implementing multiplication and division between ...
- 5,525
2
votes
1
answer
3k
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Getting an array index (0,1,2,..8) from bit masking value (1,2,4,8..256) without using log2(n). Maybe a design issue
I'm working on a component where I put in data and I get different data as a result. The input is always the same (3 Objects).
From these 3 Objects up to 9 other Objects can be calculated. One ...
- 167
2
votes
3
answers
303
views
Is there any low level way to get shifted or unshifted bits which results from bitwise operations?
I was playing with bitwise operations and a question about counting true bits of any positive integer value, so I solved the problem with bit shifting, so I just thought if there would be some way to ...
- 459
0
votes
2
answers
4k
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boolean operations in C using bitfields
I am trying to implement boolean data type in C. Basically, I am working with sets.
The following code can be used to access each bit but I am unsure whether I can represent sets using this method.
...
- 135
29
votes
11
answers
11k
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When I test out the difference in time between shifting and multiplying in C, there is no difference. Why?
I have been taught that shifting in binary is much more efficient than multiplying by 2^k. So I wanted to experiment, and I used the following code to test this out:
#include <time.h>
#include &...
- 399
2
votes
2
answers
217
views
gcc -S seems a bit misshapen with shifting and ANDing bits
Example:
int c = 4;
int p = 5;
if (p & (1 << c))
printf("ok\n");
else
printf("nop\n");
gcc -S:
movl -4(%rbp), %eax /* eax holds the variable c */
movl -8(%rbp), %edx /* ...
- 123
19
votes
4
answers
96k
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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 ...
- 319
2
votes
1
answer
992
views
Next power of 2 for a number (in search for better "bit-twiddling" way)
I just wonder if there exists better (i.e. faster?) way to get the next
power of 2 for a given number than the following one (maybe some
better sort of "bit-twiddling" hack is possible?) ...
static ...
- 151
5
votes
1
answer
7k
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 ...
- 153
4
votes
2
answers
2k
views
Concept of bit fields
Whenever I read a code like this:
struct node
{
int x : 2;
int p : 4;
}n;
with bit fields involved, I get really confused, as to how they are represented in memory, what is ...
- 1,299
14
votes
4
answers
12k
views
What's your favorite bit-wise technique? [closed]
A few days ago, StackExchange member Anto inquired about valid uses for bit-wise operators. I stated that shifting was faster than multiplying and dividing integers by powers of two. StackExchange ...
- 2,658