C++ `long long` variable type

Question

I am now studying about writing binary files. I've seen this question on StackOverflow. And the author says, in his code

const unsigned long long size = 1ULL*1024ULL*1024ULL;

I don't actually know what are the ULL symbols. Could anybody give me some documentation about it? I have searched on Google, and everything I get is more documentation about writing files...

score 4 · Accepted Answer · answered Aug 03 '13 at 07:53

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It is a suffix that specifies the type of literal (in this case, integer literals).

You can find out more about this in the C++ standard, specifically in 2.14 - Literals

In your case, the answer lies in the following table (from this very part of the standard) : unsigned long long.

Integer literals suffixes

answered Aug 03 '13 at 07:53

JBL

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BTW use the capital L instead of a lower case l as it is easy to confuse l with 1 – Ed Heal Aug 03 '13 at 08:00
Whomever authored "Table 6 -- Types of integer constants" would probably appreciate credit. – Jonathan Mee Feb 16 '16 at 19:15
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@JonathanMee I mention right above that it comes from the standard. – JBL Feb 16 '16 at 23:00

Iosif Murariu · Answer 2 · 2013-08-03T07:54:09.350

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It makes 1 and 1024 be unsigned long long constants or else they'd default to int (in terms of how many bytes the value will take to be represented):

std::cout << sizeof(1ULL) << sizeof(1);

edited Aug 03 '13 at 07:54

answered Aug 03 '13 at 07:48

Iosif Murariu

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C++ `long long` variable type

2 Answers2