View Compilation Error

0_0_21264722_16689.cpp: In function 'void multi(char*, int)':
0_0_21264722_16689.cpp:10:25: error: 'memset' was not declared in this scope
   memset(t, 0, sizeof(t));
                         ^
0_0_21264722_16689.cpp:12:15: error: 'strlen' was not declared in this scope
   l = strlen(a);
               ^
0_0_21264722_16689.cpp: In function 'void divide(char*, int, int)':
0_0_21264722_16689.cpp:32:15: error: 'strlen' was not declared in this scope
   l = strlen(c);
               ^
0_0_21264722_16689.cpp: In function 'void add(char*, char*, int)':
0_0_21264722_16689.cpp:53:16: error: 'strlen' was not declared in this scope
   l1 = strlen(a);
                ^
0_0_21264722_16689.cpp: In function 'int main(int, char**)':
0_0_21264722_16689.cpp:79:29: error: 'memset' was not declared in this scope
       memset(a, 0, sizeof(a));
                             ^