View Compilation Error

0_0_23980259_15586.cpp: In function 'int main()':
0_0_23980259_15586.cpp:10:33: error: 'memset' was not declared in this scope
         memset(a , 0 , sizeof(a)) ;
                                 ^
0_0_23980259_15586.cpp:13:28: error: 'strlen' was not declared in this scope
         int lena = strlen(a) ;
                            ^