The rev utility copies the specified files to the standard output, reversing the order of characters in every line. If no files are specified, the standard input $($from keyboard$)$ is read, and then reversed.

$8.$ Next, you need to take a look at the definition of a class, named Powerstring. Its declaration is in header file named PowerString. $h,$ and its implementation is in the file, named Powerstring.cpp$.$ You can open these two files at the same time to get a complete "picture" by typing the following command at the prompt $ :

$ vim $-0$ PowerString.h PowerString.cpp

Please note that the option is "dash uppercase O$"($it is not a zero$)$ when you type the above command.

Now you can sect that Powerstring.cpp is not complete, and this is the only source file you need to work on for this Lab Assignment. By reading the comments of each member function, it can help you complete PowerString.cpp$.$

There are different ways to reverse a string, for example, you can use a loop to scan the string from last character back to the first character; or you can define a recursive function to reverse a string; or you can do it with the Last$-$In$-$First$-$out feature of a stack: pushing the characters of a string into the stack, then popping off the stack to reverse the string. Each of the following THREE member functions is going to return a string, which is in the reverse order of the string stored in the private data member, named str: