View Compilation Error

0_0_25105530_6698.cpp: In function 'int main()':
0_0_25105530_6698.cpp:15:26: error: 'memset' was not declared in this scope
    memset(b,' ',sizeof(b));
                          ^
0_0_25105530_6698.cpp:17:20: error: 'strlen' was not declared in this scope
    int len=strlen(a);
                    ^