L4. Variables, Types, Arrays, and Hashtables

Variables and Types

PowerShell variables start with $. They can hold strings, numbers, dates, arrays, hashtables, command output, or full objects.

$name = 'Protego'
$count = 3
$now = Get-Date
$services = Get-Service
$services.GetType().FullName

PowerShell is flexible, but production scripts should still be explicit where mistakes are expensive:

[int]$retryCount = 3
[datetime]$deadline = '2026-07-15'

Arrays

Arrays hold ordered lists:

$servers = @('web01', 'web02', 'db01')
$servers[0]
$servers | ForEach-Object { "Checking $_" }

For very large collections, repeatedly using += can be inefficient. Prefer collecting pipeline output or using a generic list when performance matters.

Hashtables

Hashtables store key-value pairs:

$config = @{
  Environment = 'Prod'
  Region = 'EastUS'
  RetentionDays = 30
}
$config['Region']
$config.RetentionDays

Hashtables are also used for splatting, which makes long commands safer to read:

$params = @{
  Path = '.\report.txt'
  Value = 'Inventory complete'
  Encoding = 'utf8'
}
Set-Content @params

PSCustomObject

[pscustomobject]@{
  ComputerName = $env:COMPUTERNAME
  PowerShell = $PSVersionTable.PSVersion.ToString()
  Timestamp = (Get-Date).ToString('o')
}

Use [pscustomobject] when you want clean structured output from your own script.

Lab

1. Create an array of three hostnames.
2. Create a hashtable with environment settings.
3. Use splatting with Get-ChildItem.
4. Build a [pscustomobject] inventory record.

Sources

• Microsoft Learn: Everything you wanted to know about hashtables