View Compilation Error

0_0_34162868_4051.cpp: In constructor 'Matrix::Matrix(int, int)':
0_0_34162868_4051.cpp:12:66: error: 'memset' was not declared in this scope
     Matrix(int n = 0, int m = 0):n(n),m(m){memset(a, 0, sizeof(a));}
                                                                  ^