What does the start command actually do? [duplicate]

I tried the following experiment.

Before I start, I checked the PATH variable from cmd, which has the following value:

Path=C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;C:\ProgramData\Lenovo\ReadyApps;C:\Program Files\Microsoft SQL Server\110\Tools\Binn\;C:\Program Files\Microsoft SQL Server\120\Tools\Binn\;C:\Program Files (x86)\Windows Live\Shared;C:\Program Files (x86)\Skype\Phone\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files (x86)\Calibre2\;C:\Program Files\Intel\WiFi\bin\;C:\Program Files\Common Files\Intel\WirelessCommon\;

At first, I thought that cmd only looks for executables in the directories contained in the PATH variable, so I randomly picked an application - winword.exe (Microsoft Word), and tried to launch it from the command line:

start winword

But to my surprise, the program launches! The reason I'm surprised is because I've searched through all the directories in the PATH variable for the exe file called 'winword' but all my searches came up empty!

I've therefore concluded that the command prompt must have known to search in places other than those specified in the PATH variable to look for executables.

So obviously, the next thing I did was to look for the precise location where the 'winword' executable file is located. It turns out that winword.exe is located here:

C:\Program Files\Microsoft Office 15\root\office15

Hence giving me the idea that maybe CMD automatically looks through ProgramFiles and ProgramFiles(x86) (and all their subdirectories) when executing the 'start' command? Which led to me trying to launch another application installed on my computer, Audacity, with the exe file located at:

C:\Program Files (x86)\Audacity

Again, to my surprise, Audacity failed to launch when I typed:

start audacity

at the command line.

I've then added the directory containing audacity.exe to PATH:

set path=%path%;C:\Program Files (x86)\Audacity

after which i tried launching audacity again:

start audacity

Well, not surprisingly, Audacity launched.

What I want to know is where exactly does the command prompt look for executables? Why is it that winword.exe launches even when the directory containing it not part of PATH, but the same thing isn't true for audacity.exe?

I tried other applications too. Chrome and Firefox works when I use the start command.

UPDATE: I am running Windows version 6.3.9600 (Windows 8.1)

At first, I thought that cmd only looks for executables in the directories contained in the PATH variable, so I randomly picked an application - winword.exe (Microsoft Word) and tried to launch it from the command line:

The reason winword.exe worked is that a registry key exists which defined the path to Microsoft Word (Winword.exe). A similar key exists for Firefox.exe and Chrome.exe if those applications are installed.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths

What I want to know is where exactly does the command prompt look for executables?

System PATH Variable, User PATH Variable, and the various keys within ..\App Paths. I was able to confirm that Audacity does not create a key for itself when it's installed.

When the ShellExecuteEx function is called with the name of an executable file in its lpFile parameter, there are several places where the function looks for the file. We recommend registering your application in the App Paths registry subkey. Doing so avoids the need for applications to modify the system PATH environment variable.

• The current working directory.
• The Windows directory only (no subdirectories are searched).
• The Windows\System32 directory.
• Directories listed in the PATH environment variable.
• Recommended: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths

Source: Application Registration

From the command prompt, if you just enter WinWord it fails to run.

If you enter START WinWord it runs.

The Start command is key here.

When you try to execute a file through the start command, Command Prompt does not perform any searching. Instead, it passes the file name (and arguments) over to Windows itself (via the ShellExecuteEx API call), which must then search for the file's location. There are several places it searches in the following order:

• The current working directory.

• The Windows directory only (no subdirectories are searched).

• The Windows\System32 directory.

• Directories listed in the PATH environment variable.

• Recommended:
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths

WinWord is in that registry key. The key is there to keep PATH from getting too long.