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Null object: Difference between revisions
→{{header|C}}: Move a sentence from Undefined values#C that fits better here.
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Classic BASIC does have the concept of un-initialised or undefined variables.
=={{header|C}}==
C has the null pointer. By convention, it points to memory address zero.
There is a very common macro, <code>NULL</code>, which evaluates to <code>(void*) 0</code> or an equivalent value. NULL is compatible with all pointer types, including both data pointers and function pointers.
The standard library defines NULL in locale.h, stddef.h, stdio.h, stdlib.h, string.h, time.h and wchar.h. [[POSIX]] systems also define NULL in dirent.h and unistd.h. Many C files include at least one of these headers, so NULL is almost always available.
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