Many developers coming from modern programming languages are surprised to find that Windows batch scripting doesn't handle arithmetic expressions natively. When you try something basic like:

echo 4+2

You'll literally get "4+2" as output rather than the expected "6". This isn't a limitation of your understanding - batch files simply don't evaluate expressions directly in this way.

The classic way to perform calculations in batch scripts is using the set /a command:

set /a result=4+2
echo %result%

This will correctly output "6". The /a switch tells SET to perform arithmetic evaluation of the expression.

For more complex operations, you can chain multiple calculations:

set /a "value=(10*2)+(15/3)-5"
echo %value%

Batch supports these operators in order of precedence:

• () - grouping
• * / % - multiplication, division, modulus
• + - - addition and subtraction

You can mix variables and literals in expressions:

set num1=5
set num2=3
set /a total=num1*num2
echo %total%

Note that you don't need the % symbols when referencing variables in set /a expressions.

For quick calculations where you don't need to store the result, use:

cmd /c exit /b %((10*5)+2)%
echo %errorlevel%

This outputs "52" through the errorlevel mechanism.

Batch math has some notable constraints:

• Only integer math (no floating point)
• 32-bit signed integers (-2147483648 to 2147483647)
• No built-in power/exponent operator

For floating-point operations, you'd need to call external programs or use PowerShell integration.

Here's a basic calculator script:

@echo off
:start
set /p "expr=Enter expression: "
set /a result=%expr%
echo Result: %result%
goto start

---

When working with Windows batch scripting, you might encounter situations where you need to perform mathematical operations. Unlike many modern programming languages, batch scripts don't directly evaluate expressions like 4+2 as you might expect.

The primary way to evaluate expressions in batch scripting is using the SET /A command. This command performs arithmetic operations and stores the result in a variable:

@echo off
SET /A result=4+2
echo %result%

This will correctly output 6 to the console.

The SET /A command supports various arithmetic operators:

SET /A addition=5+3      :: 8
SET /A subtraction=5-3   :: 2
SET /A multiplication=5*3 :: 15
SET /A division=10/3     :: 3 (integer division)
SET /A modulus=10%%3     :: 1 (note the double %)

You can also use variables in your expressions:

@echo off
SET num1=4
SET num2=2
SET /A sum=num1+num2
echo The sum is %sum%

Batch scripting supports bitwise operations through SET /A:

SET /A "bitwise_and=5 & 3"   :: 1
SET /A "bitwise_or=5 | 3"    :: 7
SET /A "bitwise_xor=5 ^ 3"   :: 6
SET /A "shift_left=5 << 1"   :: 10
SET /A "shift_right=5 >> 1"  :: 2

If you need to evaluate an expression without storing the result, you can use this technique:

@echo off
for /f %%i in ('echo %= exit /b 4+2 %') do echo %%i

While SET /A is powerful, it has some limitations:

• Only integer arithmetic is supported
• Floating-point operations aren't available
• Complex expressions might require multiple steps

For more complex mathematical needs, consider:

:: Using PowerShell from batch
for /f %%i in ('powershell 4+2') do echo %%i

:: Using VBScript
echo WScript.Echo(4+2) > temp.vbs
for /f %%i in ('cscript //nologo temp.vbs') do echo %%i
del temp.vbs