View Compilation Error

0_0_27843900_7811.cpp: In function 'int main()':
0_0_27843900_7811.cpp:14:35: error: 'memset' was not declared in this scope
            memset(m, 0 ,sizeof(m) );
                                   ^
0_0_27843900_7811.cpp:16:26: error: 'strlen' was not declared in this scope
            len = strlen(a);
                          ^