View Compilation Error

0_0_37417737_23816.cpp: In function 'int main()':
0_0_37417737_23816.cpp:16:28: error: 'memset' was not declared in this scope
        memset(c,0,sizeof(c));
                            ^
0_0_37417737_23816.cpp:47:23: error: 'strlen' was not declared in this scope
            if(strlen(a)!=5)
                       ^