View Compilation Error

0_0_29330908_4231.cpp: In function 'int main()':
0_0_29330908_4231.cpp:41:21: error: 'strlen' was not declared in this scope
   int len=strlen(str);
                     ^
0_0_29330908_4231.cpp:42:10: error: 'struct m' has no member named 'date'
   arr[j].date=str[len-4]*1000+str[len-3]*100+str[len-2]*10+str[len-1];
          ^
0_0_29330908_4231.cpp:45:25: error: 'strcpy' was not declared in this scope
   strcpy(arr[j].name,str); 
                         ^