View Compilation Error

0_0_13799551_3004.cpp: In function 'int main()':
0_0_13799551_3004.cpp:14:15: error: 'strlen' was not declared in this scope
   l1=strlen(s1);
               ^
0_0_13799551_3004.cpp:16:23: error: 'memset' was not declared in this scope
   memset(s,0,sizeof(s));
                       ^