Function Manage-Services
{
    Param
    (
        [Parameter(Mandatory)]
        [ValidateSet("Start", "Stop")]
        [string[]]
        $Operation
    )
    $count = $null
    Switch ($Operation)
    {
        "Start"
        {
            for ($count = $services.Length -1; $count -ge 0; $count --)
            {
                Write-Host $services[$count]
            }
        }
        "Stop"
        {
            for ($count =0;$count -lt $services.Length; $count++)
            {
                Write-Host $services[$count]
            }
        }
    }
}