START – Windows CMD Command

Start a program, command or batch script (opens in a new window.)

Always include a TITLE this can be a simple string like “My Script” or just a pair of empty quotes “”
According to the Microsoft documentation, the title is optional, but depending on the other options chosen you can have problems if it is omitted.

If command is an internal cmd command or a batch file then the command processor is run with the /K switch to cmd.exe. This means that the window will remain after the command has been run.

In a batch script, a START command without /wait will run the program and just continue, so a script containing nothing but a START command will close the CMD console and leave the new program running.

Document files can be invoked through their file association just by typing the name of the file as a command.
e.g. START “” MarchReport.DOC will launch the application associated with the .DOC file extension and load the document.

To minimise any chance of the wrong exectuable being run, specify the full path to command or at a minimum include the file extension: START “” notepad.exe

If you START an application without a file extension (for example WinWord instead of WinWord.exe)then the PATHEXT environment variable will be read to determine which file extensions to search for and in what order.
The default value for the PATHEXT variable is: .COM;.EXE;.BAT;.CMD

Start /Wait

The behaviour of START /Wait will vary depending on the item being started, for example

The above will start the calculator and wait before continuing. However if you replace calc.exe with Winword.exe, to run Word instead, then the /wait will stop working, this is because Winword.exe is a stub which launches the main Word application and then exits.

A similar problem will occur when starting a batch file, by default START will run the equivalent of CMD /K which opens a second command window and leaves it open. In most cases you will want the batch script to complete, then just close it’s CMD console and resume the initial batch script. This can be done by explicitly running CMD /C …

Add /B to have everything run in a single window.

In a batch file, an alternative is to use TIMEOUT to delay processing of individual commands.


Starting a new process with CALL, is very similar to running START /wait, in both cases the calling script will (usually) pause until the second script has completed.

Starting a new process with CALL, will run in the same shell environment as the calling script. For a GUI application this makes no difference, but a second ‘called’ batch file will be able to change variables and pass those changes back to the caller.

In comparison START will instantiate a new CMD.exe shell for the called batch. This will inherit variables from the calling shell, but any variable changes will be discarded when the second script ends.

Run a program

To start a new program (not a batch script), you don’t have to use CALL or START, simply enter the path/file to be executed, either on the command line or within a batch script.

On the command line, CMD.EXE does not wait for the application to terminate and control immediately returns to the command prompt.
Within a command script CMD.EXE will pause the initial script and wait for the application to terminate before continuing.

If you run one batch script from another without using either CALL or START, then the first script is terminated and the second one takes over.

Multiprocessor systems

Processor affinity is assigned as a hex number but calculated from the binary positions (similar to NODRIVES)

Specifying /NODE allows processes to be created in a way that leverages memory locality on NUMA systems. For example, two processes that communicate with each other heavily through shared memory can be created to share the same preferred NUMA node in order to minimize memory latencies. They allocate memory from the same NUMA node when possible, and they are free to run on processors outside the specified node.

These two processes can be further constrained to run on specific processors within the same NUMA node.

In the following example, app1 runs on the low-order two processors of the node, while app2 runs on the next two processors of the node. This example assumes the specified node has at least four logical processors. Note that the node number can be changed to any valid node number for that computer without having to change the affinity mask.

Running executable (.EXE) files

When a file that contains a .exe header, is invoked from a CMD prompt or batch file (with or without START), it will be opened as an executable file. The filename extension does not have to be .EXE. The file header of executable files start with the ‘magic sequence’ of ASCII characters ‘MZ’ (0x4D, 0x5A) The ‘MZ’ being the initials of Mark Zibowski, a Microsoft employee at the time the file format was designed.

Command Extensions

If Command Extensions are enabled, external command invocation through the command line or the START command changes as follows:

Non-executable files can be invoked through their file association just by typing the name of the file as a command. (e.g. WORD.DOC would launch the application associated with the .DOC file extension). This is based on the setting in HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.ext\OpenWithList, or if that is not specified, then the file associations – see ASSOC and FTYPE.

When executing a command line whose first token is the string CMD without an extension or path qualifier, then CMD is replaced with the value of the COMSPEC variable. This prevents picking up CMD.EXE from the current directory.

When executing a command line whose first token does NOT contain an extension, then CMD.EXE uses the value of the COMSPEC environment variable. This prevents picking up CMD.EXE from the current directory.

When executing a command line whose first token does NOT contain an extension, then CMD.EXE uses the value of the PATHEXT environment variable to determine which extensions to look for and in what order. The default value for the PATHEXT variable is: .COM;.EXE;.BAT;.CMD Notice the syntax is the same as the PATH variable, with semicolons separating the different elements.

When searching for an executable, if there is no match on any extension, then looks to see if the name matches a directory name. If it does, the START command launches the Explorer on that path. If done from the command line, it is the equivalent to doing a CD /D to that path.


If the command is successfully started ERRORLEVEL =unchanged, typically this will be 0 but if a previous command set an errorlevel, that will be preserved (this is a bug).
If the command fails to start then ERRORLEVEL = 9059
START /WAIT batch_file – will return the ERRORLEVEL specified by EXIT


Run a minimised Login script:
START "My Login Script" /Min Login.cmd

Start a program and wait for it to complete before continuing:
START "" /wait autocad.exe

Open a file with a particular program:
START "" "C:\Program Files\Microsoft Office\Winword.exe" "D:\Docs\demo.txt"

Open Windows Explorer and list the files in the current folder (.) :
C:\any\old\directory> START .

Connect to a new printer: (this will setup the print connection/driver )
START \\print_server\printer_name

Start an application and specify where files will be saved (Working Directory):
START /D C:\Documents\ /MAX "Maximised Notes" notepad.exe

START is an internal command.

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