//Computer code always runs from top to bottom. The only way to go "backwards"
			//is to use "checkpoints" you can go back to, as explained a little further below.
			//Batch is just a "script" of sorts that the CMD will follow, like an actor for a movie.
			//It will follow what's written on the script from start to finish.

			//NOTE : ^ is a special character that allows us to use letters like ? and _ in echo
			//commands. Don't let it bother you too much for now, just pretend it isn't there.

			//Here I will write code that will automatically rename file extensions in mass.

			//First things first, I want to make commands invisible to the user so things don't get
			//cluttered.


@echo off	//When a command is launched in the CMD, it gets displayed on the screen.
			//@ runs a command *without* displaying it in the command prompt.
			//Therefore, we can run "echo off" here without it displaying in the window.

			//What "echo off" does is simply hide all the next commands the same way
			//@ did with "echo off".


:MAIN		//:MAIN is a "checkpoint" that you can go back to within the code.
			//If you write "goto MAIN", the CMD will be send back up to where :MAIN is, and
			//will start reading code from that point on.


cls			//cls just clears what's written on the screen.
			//It isn't needed in this case, but you're always safer adding it and not needing it
			//than not adding it and needing it.


echo MASS EXTENSION CHANGER				//These three lines are messages that I demand the CMD to
echo.									//display. They will be displayed even if "echo off" was run
echo Original extension, no period ^:	//beforehand. You can use "echo." to display a blank line, or
										//"echo message" to display a message.


set /p ex1=^>							//set defines a variable. /p is a "switch" that you add after the
										//command to tell it how to do it's job. For an example, if you add
										///p after set, you'll tell set to display a Prompt.
										//ex1 is the variable you're modifying.

										//The standard formatting for a variable is just
										//thing1=thing2, but in this scenario, what's after the = is
										//whatever the user writes, so we write a message there to be
										//displayed on the screen instead.

										//Here ex1 (extension 1) will be defined as whatever the user writes.
										//To use the variable's value within our code, we will write %ex1%, or !ex1!.
										//The difference between the two doesn't matter in simple programs, so just use
										//whichever one you like most for now.


echo.									//Now we ask for the user to tell us what he'd like his extensions
echo Target extension, no period ^:		//changed to, and display a message for it.


set /p ex2=^>							//Here is the same story as above, except we're defining "ex2".


echo.																	//Here we confirm the user's choice.
echo Change all .%ex1% files in the current folder to .%ex2% files^^?	//I have used variables within echo to
																		//display whatever the user typed in.


choice									//The choice command gives the user a simple Y/N choice. It can be
										//configured to accept more letters, display a message, ect, but just
										//focus on the Y/N part for now.

										//If the user presses Y, it will set the variable errorlevel to 1 because
										//Y is the first choice in Y and N.

										//If the user presses N, it will set the variable errorlevel to 2 because
										//N is the second choice in Y and N.


if %errorlevel%==2 goto MAIN			//The if command allows us to run commands under certain circumstances only.
										//In this case, in plain english, if %errorlevel% = 2, go to the checkpoint MAIN.
										//If the user pressed N, the program will go back to the MAIN checkpoint up above.

										//If the user did NOT press N, then that means that he obviously pressed Y, which
										//means we can move on to the actual work.


rename *.%ex1% *.%ex2%					//The rename command doesn't do ten different things - It renames.
										//In Windows in general, * refers to "everything". Which means here that
										//"everything that has .%ex1% gets renamed to filename.%ex2%".

										//Example :
										//If %ex1% = jpg_large, %ex2% = jpg, then it will rename all files named
										//"*whatever*.jpg_large" to "*whatever*.jpg".


echo.									//If the code made it this far with no errors, we can assume it went fine.
echo Job complete.						//We tell the user about it.


pause									//We pause the program so the user can read the message, and then close the window.
										//The pause command pauses a program and waits for the user to press a key to continue.


				//If there is nothing left in the script for the CMD to read, it will close on it's own.
				//Hence why I placed "pause" at the very end.