What Is a Variable?

A **variable** is basically a box that stores a value: text, numbers, paths, anything. You can change the value anytime and use it anywhere in your script.

set name=Kaloyan
echo Hello %name%
      

Output:

Hello Kaloyan
      

Important Rule

In Batch, you **set** variables without percent signs, and you **use** them with percent signs.

set age=12
echo You are %age% years old.
      

Asking the User for Input

You can ask the user to type something using set /p:

set /p username=Enter your username: 
echo Welcome, %username%!
      

Variables Inside Loops (Delayed Expansion)

Batch normally doesn’t update variables inside loops unless you enable something called Delayed Expansion.

@echo off
setlocal enabledelayedexpansion

set count=0

for %%i in (1 2 3 4 5) do (
  set /a count+=1
  echo Count is now: !count!
)
      

Notice how variables inside loops use !exclamation marks! instead of %percent signs%.

Math With Variables (set /a)

You can do simple math:

set /a x=5+10
set /a y=x*2
echo %y%
      

Output:

30
      

Environment Variables

Windows has built-in system variables you can read:

echo Username: %USERNAME%
echo Windows Directory: %WINDIR%
echo Computer Name: %COMPUTERNAME%
      

Useful Example – Auto Backup Script

@echo off

set source=C:\Users\%USERNAME%\Documents
set backup=D:\Backups\%date%

echo Backing up files...
xcopy "%source%" "%backup%" /e /i /y

echo Backup complete!
pause
      

Variables make your scripts cleaner, reusable, and way easier to modify.

What’s Next?

Next you’ll learn how functions and procedures work in Python.