View Compilation Error

0_0_23515645_17325.cpp: In function 'int main()':
0_0_23515645_17325.cpp:11:36: error: 'isalpha' was not declared in this scope
         if(a[0]!='_'&&!isalpha(a[0]))
                                    ^
0_0_23515645_17325.cpp:18:29: error: 'isalnum' was not declared in this scope
             if(!isalnum(a[i])&&!a[i]='_')
                             ^