Mastering Windows PowerShell Scripting - Third Edition

Default values

Parameters may be given default values by using assignment statements in the param block, such as the following, for example:

param (    [String]$Parameter1 = 'DefaultValue')

If the assignment is the result of a command, the command must be placed in parentheses:

param (    [String]$ProcessName = (Get-Process -Id $PID | Select-Object -ExpandProperty Name))

Value types, such as Boolean, or Int32 and other numeric types, are initialized with a default value for that type. For instance, a parameter of the Boolean type can never be null; it will default to false. Numeric values will default to 0. Setting a default false value for a Boolean parameter is therefore unnecessary.

Assigning a default value was the basis for making parameters ...