What does the 'ULL' suffix mean in numeric literals in C/C ?

The Significance of the "ULL" Suffix in Numeric Literals

In programming, we often encounter code involving numeric literals and modifiers to specify their data type. In particular, the "ULL" suffix has been observed in certain scenarios. Let's delve into its purpose.

As you've mentioned, the "U" and "L" characters are not valid hex digits. To clarify their significance, let us refer to the C/C language specifications.

C/C Specifications:

According to the GCC manual, the "LL" suffix denotes an integer constant of type "long long int." Similarly, the "ULL" suffix is used to represent an integer constant of type "unsigned long long int." These suffixes ensure that the resulting value has the desired precision and data range.

Usage in Code:

In the code example you provided:

line += addr & 0x3fULL;

The "& 0x3fULL" operation effectively masks the lower 6 bits of the "addr" variable using the "unsigned long long int" data type. This ensures that the resulting value is stored in that data type, which may be required for further calculations or compatibility with other code components.

Conclusion:

In essence, the "ULL" suffix on a numeric literal indicates an unsigned long long integer constant, as defined in the C/C language specifications. It allows programmers to explicitly declare the type and range of the value, ensuring precision and compatibility in their code.

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