Windows 7 / Getting Started

System Variables Identify the Environment

Many system variables are available within Windows 7, and you'll see these often when using the command prompt and Windows PowerShell. They are useful in identifying specific information about the environment, without actually knowing the current environment. As a simple example, every computer has a computer name, but the computer names are different. However, the system variable %computername% holds the value of the local computer's computer name.

System variables are easy to identify. They always start and end with a percent symbol (%). An easy way to view the value of any variable is by using the echo command in the following format:

Echo %variableName%

Table below shows many of the commonly used system variables and their value.

Some commonly used system variables

VariableValue
%windir%
%systemroot%		Both %windir% and %systemroot% identify the folder where Windows was installed, typically C:\Windows.
%systemdrive%The folder where the system boot files are located, typically C:\.
%computername%The name of the local computer
%username%The name of the user logged on to this session
%date%Holds the value of the current date in the format ddd mm/dd/yyyy The first three letters are an abbreviation of the day such as Mon, Tue, Wed, and so on The remaining format is all numbers with mm for the month, dd for the day, and yyyy for the year
%time%Holds the value of the current time in a 24-hour format as hh.mm.ss.ms
%errorlevel%Indicates whether the previous command resulted in an error If it didn't have an error, the value is 0.
%ProgramFiles%Points to the location of the Program Files folder, which is normally C:\Program Files.
%Public%The location of the Public folder, typically C:\Users\Public.
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In this tutorial:

  1. Working with the Command Prompt
  2. Starting and Ending a Command Prompt Session
  3. Easy ways to invoke administrator Command Prompt sessions
  4. Starting Command Prompt at a Particular Folder
  5. Strings with Spaces Need Quotes
  6. Cmd.exe vs. Command.com
  7. Commands Are Not Case Sensitive
  8. Starting Command Prompt and Running a Command
  9. Cmd.exe and Other Command Prompts
  10. Using AutoRun to Execute Commands When Command Prompt Starts
  11. Using Cmds Command-Line Syntax
  12. Using Commands
  13. Type /? for help
  14. Starting Programs
  15. Open Windows Explorer at the current Command Prompt folder
  16. Using File-Name and Folder-Name Completion
  17. Use a different completion character
  18. Using Wildcards
  19. Editing the Command Line
  20. Using Command Symbols
  21. The Redirection Symbols
  22. The Pipe Symbol
  23. The Command Combination Symbols
  24. Pausing or Canceling Commands
  25. Simplifying Command Entry with Doskey Macros
  26. DOSKEY Saves Typing
  27. System Variables Identify the Environment
  28. Viewing Environment Variables
  29. Modifying Environment Variables
  30. Predefined Environment Variables
  31. Customizing Command Prompt Windows
  32. Setting the Window Size and Position
  33. Setting the Window Size and Position Visually
  34. Selecting a Font
  35. Setting Colors
  36. Setting Other Options
  37. Copy and paste in the command prompt window
  38. Navigating from the command prompt
  39. Printing a list of filenames
  40. Commands Use Paths
  41. Identifying Executables
  42. Modifying the Path to Executables
  43. Modifying the Path with the GUI
  44. Changing the Current Path with CD
  45. Changing the Current Path with Windows Explorer
  46. Capturing the Output
  47. A Sampling of Commands
  48. Dir
  49. Copy
  50. XCopy
  51. SET
  52. NET USE
  53. SystemInfo
  54. DriverQuery
  55. Echo
  56. Advanced Shell Commands
  57. Creating a Batch File
  58. Scheduling a Batch File
  59. Creating Scheduled Tasks with a Script
  60. Using Windows PowerShell and the PowerShell ISE
  61. Windows PowerShell ISE
  62. PowerShell Commands
  63. Verbs and Nouns
  64. Sending Output to a Text File
  65. PowerShell Syntax
  66. Variables Created with a $ Symbol
  67. Comparison Operators
  68. Parentheses, Brackets, and Braces
  69. Running PowerShell Scripts
  70. PowerShell Execution Policy
  71. Changing the Execution Policy
  72. Looping
  73. Collections
  74. Creating a PowerShell Script
  75. Documenting Scripts
  76. Using PowerShell Commands
  77. Getting Help on PowerShell
  78. Using WMI_Cmdlets
  79. Getting Details on an Object
  80. Querying Information on Specific Objects
  81. Terminate Applications with Win32_process
  82. Formatting Output with the -f Format Operator
  83. Filtering the Output with the Where-Object Command
  84. Using the IF statement
  85. Using the Switch Statement
  86. Script Reusability