omnet++ - C++ clarification -

i doing c++ code in omnet++ simulator came across piece of code. can please explain hpw sequence working ?

char *st = "data.enc";  std::ofstream myfile; myfile.open(st,std::ios_base::app); //please provide explnation line  printf("\n aes encryption:\n"); for(i=0;i<4*4;i++) {     printf("%02x ",out[i]+l);      myfile <<out[i]+l<<"\n"; }  printf("%02x ",out[i]);//what out[i] ? myfile.close(); printf("\n\n"); 

std::ofstream myfile; myfile.open(st,std::ios_base::app); //please provide explnation line 

opens file in append mode. means insertions appended end of file instead of overwriting it.

for(i=0;i<4*4;i++) {     printf("%02x ",out[i]+l);      myfile <<out[i]+l<<"\n"; } 

takes 16 first elements in out and:

printf("%02x ",out[i]+l); 

prints them in hexadecimal format if bytes. 0 means fill 0s until reaching desired length (2). x means print in hexadecimal.

myfile <<out[i]+l<<"\n"; 

appends contents of out adding 1.

printf("%02x ",out[i]);//what out[i] ? 

prints out[16] (this time without adding one) in 2 digit hexadecimal format.

myfile.close(); 

closes file.

printf("\n\n"); 

prints 2 blank lines.