View Compilation Error

0_0_23566427_17058.cpp: In function 'int covert(char*)':
0_0_23566427_17058.cpp:3:21: error: 'strcmp' was not declared in this scope
  if(!strcmp(s,"zero")) return 0;  
                     ^
0_0_23566427_17058.cpp: In function 'int main()':
0_0_23566427_17058.cpp:21:23: error: 'scanf' was not declared in this scope
   for(a=0,scanf("%s",s);s[0]!='+';scanf("%s",s))  
                       ^
0_0_23566427_17058.cpp:23:23: error: 'scanf' was not declared in this scope
   for(b=0,scanf("%s",s);s[0]!='=';scanf("%s",s))  
                       ^
0_0_23566427_17058.cpp:26:20: error: 'printf' was not declared in this scope
   printf("%d\n",a+b);  
                    ^