View Compilation Error

0_0_22084667_10795.cpp: In function 'void big_Mult_small(char*, int, char*)':
0_0_22084667_10795.cpp:14:27: error: 'memset' was not declared in this scope
     memset(m, 0, sizeof(m));
                           ^
0_0_22084667_10795.cpp:16:23: error: 'strlen' was not declared in this scope
     int len = strlen(a);
                       ^
0_0_22084667_10795.cpp: In function 'int main()':
0_0_22084667_10795.cpp:54:31: error: 'memset' was not declared in this scope
         memset(a, 0, sizeof(a));
                               ^
0_0_22084667_10795.cpp:60:24: error: 'strcpy' was not declared in this scope
             strcpy(a, s);
                        ^
0_0_22084667_10795.cpp:62:32: error: 'strlen' was not declared in this scope
         for(int i=0; i<strlen(s); ++i)
                                ^