View Compilation Error

0_0_16462798_27616.cpp: In function 'node multiply(node, node)':
0_0_16462798_27616.cpp:17:43: error: 'memset' was not declared in this scope
     memset(res.matrix,0,sizeof(res.matrix));
                                           ^
0_0_16462798_27616.cpp: In function 'int main()':
0_0_16462798_27616.cpp:70:53: error: 'memset' was not declared in this scope
         memset(series.matrix,0,sizeof(series.matrix));
                                                     ^