View Compilation Error

0_0_22183240_18152.cpp: In function 'int main()':
0_0_22183240_18152.cpp:27:30: error: 'memset' was not declared in this scope
   memset(num,'\0',sizeof(num));
                              ^
0_0_22183240_18152.cpp: In function 'int fun2(int)':
0_0_22183240_18152.cpp:40:29: error: 'memset' was not declared in this scope
  memset(num,'\0',sizeof(num));
                             ^