View Compilation Error

0_0_37599811_12773.cpp: In function 'int main()':
0_0_37599811_12773.cpp:36:20: error: 'strlen' was not declared in this scope
   int sa = strlen(a), sb = strlen(b);
                    ^
0_0_37599811_12773.cpp:38:11: error: 'sb' was not declared in this scope
   zero(b, sb);
           ^
0_0_37599811_12773.cpp:39:18: error: 'strcmp' was not declared in this scope
   if (strcmp(a, b) == 0)
                  ^