Issue while executing powershell script

test.ps  contains 

$letterArray = "a","b","c","d"

          foreach ($letter in $letterArray)

          {

              Write-Host $letter

          }

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PS C:\> c:\test.ps1

The term 'c:\test.ps1' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the

 spelling of the name, or if a path was included, verify that the path is correct and try again.

At line:1 char:12

+ c:\test.ps1 <<<<

    + CategoryInfo          : ObjectNotFound: (c:\test.ps1:String) [], CommandNotFoundException

    + FullyQualifiedErrorId : CommandNotFoundException