View Compilation Error

0_0_18065938_12627.cpp: In function 'int main()':
0_0_18065938_12627.cpp:11:33: error: 'memset' was not declared in this scope
         memset(sum,0,sizeof(sum));
                                 ^
0_0_18065938_12627.cpp:13:38: error: 'strcmp' was not declared in this scope
         while(cin>>str,strcmp(str,"0")){
                                      ^
0_0_18065938_12627.cpp:14:31: error: 'strlen' was not declared in this scope
             for(i=j=strlen(str)-1;0<=i;i--)
                               ^