CMD opens and closes all of a sudden. (batch file coding) - batch-file

Question

This is a simple calculator:
#ECHO OFF
TITLE Simple Calculator
ECHO if you want to add press 1,subtract 2,multiply 3 and divide 4
set /a selection =
if %selection%== "1" goto add
if %selection%== "2" goto sub
if %selection%== "3" goto multiply
if %selection%== "4" goto divide
:add
ECHO Type the first number you wish to add:
SET /P Numadd1=
ECHO Type the second number you want to add to the first number:
SET /P Numadd2=
ECHO.
SET /A Ansadd=%Numadd1%+%Numadd2%
ECHO The result is: %Ansadd%
ECHO.
ECHO Press any key to exit.
PAUSE>nul
:sub
ECHO Type the first number you wish to subtract with:
SET /P Numsub1=
ECHO Type the second number you want to subtract from %Numsub1%:
SET /P Numsub2=
ECHO.
SET /A Ansub=%Numsub1%-%Numsub2%
ECHO The result is: %Ansub%
ECHO.
ECHO Press any key to exit.
PAUSE>nul
:multiply
ECHO Type the first number you wish to multiply:
SET /P Nummul1=
ECHO Type the second number you want to multiply with the first number:
SET /P Nummul2=
ECHO.
SET /A Ans=%Nummul1%+%Nummul2%
ECHO The result is: %Ansmul%
ECHO.
ECHO Press any key to exit.
PAUSE>nul
:divide
ECHO Type the first number you wish to divide:
SET /P Numdiv1=
ECHO Type the second number you want to divide with the first number:
SET /P Numdiv2=
ECHO.
SET /A Ansdiv=%Numdiv1%+%Numdiv2%
ECHO The result is: %Ansdiv%
ECHO.
ECHO Press any key to exit.
PAUSE>nul
May I know what is the problem with this and the correct code?

Answer 1

There were too many issues to mention in the comment section so please take a look at this example against yours to see if you can identify them:
#ECHO OFF
TITLE Simple Calculator
SET /P "Selection=Enter + to Add, - to Subtract, * to Multiply or / to Divide: "
IF "%Selection%"=="+" GOTO Add
IF "%Selection%"=="-" GOTO Subtract
IF "%Selection%"=="*" GOTO Multiply
IF "%Selection%"=="/" GOTO Divide
GOTO :EOF
:Add
SET /P "Numadd1=Enter an addend: "
SET /P "Numadd2=Enter another addend: "
SET /A Ansadd=Numadd1+Numadd2
ECHO.
ECHO The sum is: %Ansadd%
ECHO.
PAUSE
GOTO :EOF
:Subtract
SET /P "Numsub1=Enter the minuend: "
SET /P "Numsub2=Enter the subtrahend: "
SET /A Ansub=Numsub1-Numsub2
ECHO.
ECHO The difference is: %Ansub%
ECHO.
PAUSE
GOTO :EOF
:Multiply
SET /P "Nummul1=Enter a factor:"
SET /P "Nummul2=Enter another factor: "
SET /A Ansmul=Nummul1*Nummul2
ECHO.
ECHO The product is: %Ansmul%
ECHO.
PAUSE
GOTO :EOF
:Divide
SET /P "Numdiv1=Enter the dividend: "
SET /P "Numdiv2=Enter the divisor: "
SET /A Ansdiv=Numdiv1/Numdiv2
ECHO.
ECHO The quotient is: %Ansdiv%
ECHO.
PAUSE
Ideally you should make sure that none of your variables have existing values at the start of the script and check that the entered values are compatible/validated before using them too!
Edit
You could probably make the code shorter too:
#ECHO OFF
TITLE Simple Calculator
FOR %%A IN (Operator Integer1 Integer2 Result) DO SET "%%A="
SET /P "Operator=Enter + to Add, - to Subtract, * to Multiply or / to Divide: "
IF DEFINED Operator (SET "Operator=%Operator:~,1%") ELSE GOTO :EOF
ECHO(%Operator%|FINDSTR /L "+ - * /">NUL||GOTO :EOF
SET /P "Integer1=Enter your starting integer: "
SET /P "Integer2=Now the other integer: "
SET /A Result=Integer1 %Operator% Integer2
ECHO(
ECHO The Answer is: %Result%
ECHO(
PAUSE

Answer 2

These two lines
ECHO if you want to add press 1,subtract 2,multiply 3 and divide 4
set /a selection =
should be:
set /p selection=if you want to add press 1,subtract 2,multiply 3 and divide 4:

Answer 3

There are a few errors in your code, including the math. Try and take a look at my code and compare it with yours.
#ECHO OFF
TITLE Simple Calculator
echo If you want to add press 1, subtract 2, multiply 3 and divide 4
set /p selection=
if "%selection%"=="1" goto add
if "%selection%"=="2" goto sub
if "%selection%"=="3" goto multiply
if "%selection%"=="4" goto divide
:add
ECHO Type the first number you wish to add:
SET /P Numadd1=
ECHO Type the second number you want to add to the first number:
SET /P Numadd2=
SET /A Ans=%Numadd1%+%Numadd2%
goto end
:sub
ECHO Type the first number you wish to subtract with:
SET /P Numsub1=
ECHO Type the second number you want to subtract from %Numsub1%:
SET /P Numsub2=
SET /A Ans=%Numsub1%-%Numsub2%
goto end
:multiply
ECHO Type the first number you wish to multiply:
SET /P Nummul1=
ECHO Type the second number you want to multiply with the first number:
SET /P Nummul2=
SET /A Ans=%Nummul1%*%Nummul2%
goto end
:divide
ECHO Type the first number you wish to divide:
SET /P Numdiv1=
ECHO Type the second number you want to divide with the first number:
SET /P Numdiv2=
SET /A Ans=%Numdiv1%/%Numdiv2%
:end
ECHO.
ECHO The result is: %Ans%
ECHO.
ECHO Press any key to exit.
PAUSE>nul