View Compilation Error

0_0_18024827_30962.cpp: In function 'void update(LineTree*, int, int)':
0_0_18024827_30962.cpp:52:21: error: 'strcmp' was not declared in this scope
   if(strcmp(ch,"Add")==0)
                     ^
0_0_18024827_30962.cpp: In function 'int main()':
0_0_18024827_30962.cpp:93:22: error: 'strcmp' was not declared in this scope
    if(strcmp(ch,"End")==0)
                      ^
0_0_18024827_30962.cpp:96:24: error: 'strcmp' was not declared in this scope
    if(strcmp(ch,"Query")==0)
                        ^