View Compilation Error

0_0_34098347_31612.cpp: In constructor 'Matrix::Matrix(int, int)':
0_0_34098347_31612.cpp:9:67: error: 'memset' was not declared in this scope
     Matrix (int n = 0, int m = 0):n(n),m(m){memset(a, 0, sizeof(a));} 
                                                                   ^