View Compilation Error

0_0_26339078_15055.cpp: In function 'int findPointPos(char*)':
0_0_26339078_15055.cpp:18:23: error: 'strlen' was not declared in this scope
     int len = strlen(a);  
                       ^
0_0_26339078_15055.cpp: In function 'void reverse(char*)':
0_0_26339078_15055.cpp:29:23: error: 'strlen' was not declared in this scope
     int len = strlen(a);  
                       ^
0_0_26339078_15055.cpp: In function 'void multiply(char*, char*, char*)':
0_0_26339078_15055.cpp:42:24: error: 'strlen' was not declared in this scope
     int alen = strlen(a);  
                        ^
0_0_26339078_15055.cpp: In function 'int main()':
0_0_26339078_15055.cpp:78:27: error: 'strlen' was not declared in this scope
         int len = strlen(a);  
                           ^
0_0_26339078_15055.cpp:106:25: error: 'strcpy' was not declared in this scope
         strcpy(result, a);  
                         ^
0_0_26339078_15055.cpp:109:41: error: 'memset' was not declared in this scope
         memset(tempa, '0', sizeof(tempa));  
                                         ^