View Compilation Error

0_0_22961449_24003.cpp: In function 'int main()':
0_0_22961449_24003.cpp:12:27: error: 'memset' was not declared in this scope
   memset(tab,0,sizeof(tab));
                           ^
0_0_22961449_24003.cpp:13:19: error: 'strlen' was not declared in this scope
   alen  = strlen(a);
                   ^