View Compilation Error

0_0_34901446_3570.cpp: In function 'int main()':
0_0_34901446_3570.cpp:11:19: error: 'strlen' was not declared in this scope
 for(j=0;j<strlen(a);j++)
                   ^
0_0_34901446_3570.cpp:16:15: error: 'strlen' was not declared in this scope
 if(j==strlen(a)) printf("yes\n");
               ^