What is the meaning of "1ULL"in c programming language

Question

for (x = 0; x < 1ULL<<(2*length); ++x){

this above line is a c program code which I downloaded. It has a part "1ULL". First I thought it was a mistake. but the code compiles and works well. can anyone please explain me what is that thing mean.

thank you....

@H2CO3: I am, for instance. Just because the answer is easily googled, it doesn't meant that it's a bad question. — Nathan Fellman, Jul 22 '13 at 19:27
@H2CO3: Note that unlike in the linked "duplicate", the use of the suffix in the code here is significant and likely required (e.g. if `int` is 32 bits, the code would malfunction if the prefix were omitted and `length` could be 16 or larger). — supercat, Jul 22 '13 at 19:29
Being new to C (more comfortable with Python), I did not recognize this "1ULL" expression as the combination of a numeric literal and type suffix. Visually, it looks more like "NULL" than it looks like "1". The specific form of this question was helpful to me; the marked duplicate did not show up when searching. — David Brown, Dec 24 '21 at 15:39
I'm upvoting this, as this version of the question is clearer and completer. Not a reason for an upvote, but it was also the first google Result I got. — Erik Bongers, Jan 26 '22 at 10:39

score 20 · Answer 1 · edited May 23 '17 at 12:33

20

Suffix ULL to an integer represents type specifier. It means

unsigned long long

You may also like to read this and this one for more detail.

edited May 23 '17 at 12:33

Community

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answered Jul 22 '13 at 19:25

haccks

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Brian Cain · Answer 2 · 2013-07-22T19:30:54.787

9

Those letters modify the literal 1 and make it of type unsigned long long.

This is covered in C99 (ISO/IEC 9899) §6.4.4.1 Integer constants:

integer-suffix:
unsigned-suffix long-suffixopt
unsigned-suffix long-long-suffix
long-suffix unsigned-suffixopt
long-long-suffix unsigned-suffixopt
unsigned-suffix: one of
u U
long-suffix: one of
l L
long-long-suffix: one of
ll LL

edited Jul 22 '13 at 19:30

answered Jul 22 '13 at 19:24

Brian Cain

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I already vote all of you, but I think answers are incomplete till you don't tell usability of it. – Grijesh Chauhan Jul 22 '13 at 19:33
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for example `sizeof(1) != sizeof(1ULL)`. – Grijesh Chauhan Jul 22 '13 at 19:35
This is the only answer that properly addresses what the `1` is in `1ULL`. Upvoted. – conchoecia Dec 06 '18 at 23:11

score 6 · Answer 3 · answered Jul 22 '13 at 19:25

6

It's a way to signal to the compiler that the value must be considered as a unsigned long long.

answered Jul 22 '13 at 19:25

nouney

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What is the meaning of "1ULL"in c programming language

3 Answers3

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