if (memcmp (version, "\x0\x0\x0", 3) == 0 )

I am working on a piece of code that has a statement as below:

if (memcmp (version, "\x0\x0\x0", 3) == 0 )       

What is the data that is being compared with version? Is it the same a开发者_开发技巧s comparing with "000"?

No, it is not the same as "000". It is comparing three null (0) bytes. Each byte is an actual value of zero in binary. This is different than "000", which is a string containing ASCII values for the printable character 0, which is 48 (or 30 in hex.)

So "000" would be the same as "\x30\x30\x30".

"\x0\x0\x0" equals { 0x00, 0x00, 0x00, 0x00 }. The fourth zero is the string null terminator.

So to answer your question - no, it's not the same as comparing with "000".

'\x0' is hexadecimal zero, whereas '0' is the ASCII code of the character 0 (hexadecimal 30).

No - it's not same as comparing against "000". It's comparing against three null characters. An equivalent, and probably more expected, string would be "\0\0\0". Or just a 3-character array filled with 0, for this case, where the code is only checking 3 characters anyway.

\x0 stands for a char with value 0. 0 is different, it's the ASCII character with code 0x30.

It would be interesting to know the definition of the variable version. Is it a void * or a char * or some other strange casting. This is probably throwing up a warning during compilation.

It would also be prudent to look at how version is initialised just to make sure there are no errors. It is certainly a strange way to check for (the lack of a) version number in a program.

No. \x0 is the literal for NULL. "000" is a number and have a different representation in memory.