View Compilation Error

0_0_25010275_18304.cpp: In function 'int main()':
0_0_25010275_18304.cpp:9:28: error: 'strlen' was not declared in this scope
             len1=strlen(str);  
                            ^
0_0_25010275_18304.cpp:11:27: error: 'memset' was not declared in this scope
     memset(ar,0,sizeof(ar));  
                           ^