View Compilation Error

0_0_35850070_25677.cpp: In function 'void change(char*)':
0_0_35850070_25677.cpp:9:38: error: 'strlen' was not declared in this scope
     int left = 0 ,right =strlen (str )- 1 ;
                                      ^
0_0_35850070_25677.cpp: In function 'void Add(char*, char*)':
0_0_35850070_25677.cpp:28:30: error: 'strcpy' was not declared in this scope
     strcpy (str1 +i ,str2 +i );
                              ^
0_0_35850070_25677.cpp: In function 'void print(char*)':
0_0_35850070_25677.cpp:44:24: error: 'strlen' was not declared in this scope
     int i =strlen (str )- 1 ;
                        ^