View Compilation Error

0_0_36051009_31637.cpp: In function 'int main()':
0_0_36051009_31637.cpp:7:33: error: 'strcmp' was not declared in this scope
       while(cin>>a&&strcmp(a,"#"))
                                 ^
0_0_36051009_31637.cpp:11:19: error: 'strlen' was not declared in this scope
       len=strlen(b);
                   ^
0_0_36051009_31637.cpp:12:31: error: 'strstr' was not declared in this scope
          for(p=a;(p=strstr(p,b))!=NULL;num++,p+=len);
                               ^