Why do integers in PowerShell compare by digits?

This is because you're comparing a string to an integer. The order matters.

"56" -lt 7

Is actually the same as:

"56" -lt "7"

Alternatively:

56 -lt "7"

would give you the correct result. PowerShell tries to coerce the right side argument to the type of the left side.

You might try an explicit cast:

[int]$Input -lt $GeneratedNum

The trouble come from the fact that Read-Host return a string so with your cast $Input is an ArrayListEnumeratorSimple try :

[int]$GeneratedNum = Get-Random -min 1 -max 101Write-host $GeneratedNum$isQuitting = $falseDo{    $Input = (Read-Host "Take a guess!") -as [int]    If($Input -lt $GeneratedNum){Write-Output "Too Low"}    If($Input -gt $GeneratedNum){Write-Output "Too High"}    If($Input -eq $GeneratedNum){Write-Output "Good Job!"; $isQuitting = $true}} Until($isQuitting -eq $true)

You also should use try{}catch{} to catch the case the input is not an int.

The thing you must understand is that when you use PowerShell comparison operators, the type of the left part is used selected, so the rigth part is casted into the left type. Knowing that you could have write the following, where I just put the $GeneratedNum which is an integer on the left of the comparisons:

[int]$GeneratedNum = Get-Random -min 1 -max 101Write-host $GeneratedNum$isQuitting = $falseDo{    $Input = (Read-Host "Take a guess!")    If($GeneratedNum -gt $Input){Write-Output "Too Low"}    If($GeneratedNum -lt $Input){Write-Output "Too High"}    If($GeneratedNum -eq $Input){Write-Output "Good Job!"; $isQuitting = $true}} Until($isQuitting -eq $true)

Never use a variable with the same name as an automatic variable: $input is an automatic variable.

See this code, where I pipe the value read from host (and don't use the $input variable):

[int]$GeneratedNum = Get-Random -min 1 -max 101Write-Debug $GeneratedNum$isQuitting = $falseDo{    Read-Host "Take a new guess!" | %{        if($_ -as [int] -gt 0){            If($_ -lt $GeneratedNum){Write-Output "Too Low"}            If($_ -gt $GeneratedNum){Write-Output "Too High"}            If($_ -eq $GeneratedNum){Write-Output "Good Job!"; $isQuitting = $true}        }    }} Until($isQuitting -eq $true)

Important to notice that my code treats correctly wrong inputs (non numeric characters) like w or like strings (qwerty), which make the other proposals to fail.

I make use of the fact that you generate integers always greater than 0.