The bzero is not in standard (ANSI) C function, it appeared in 4.3BSD (Berkeley UNIX C library). Its prototype existed previously in <string.h> before it was moved to <strings.h> for IEEE Std 1003.1-2001 (``POSIX.1'') compliance.
To use it in ANSI C you have to define it first(Some system do this work). memset, on the other hand, pre-exists and has a known meaning.
This function is deprecated (marked as LEGACY in POSIX.1-2001): use memset in new programs.
This is a partially obsolete alternative for
memset, derived from BSD. Note that it is not as general as
memset, because the only value it can store is zero.
function conforms to ISO/IEC 9899:1990 (``ISO C90'').It was adopted by the System V, ANSI C and POSIX standards and bzero deprecated.
When porting to Solaris, here is possible ANSI/POSIX/SVR4 replacements for popular BSD functions: