Assoc

Most files in Windows are associated with a specific program that is assigned to open the file by default. At times, remembering these associations can become confusing. You can remind yourself by entering the command assoc to display a full list of filename extensions and program associations.

You can also extend the command to change file associations. For example, assoc .txt= will change the file association for text files to whatever program you enter after the equal sign. The assoc command itself will reveal both the extension names and program names, which will help you properly use this command.

In Windows 10, you can view a more user-friendly interface that also lets you change file type associations on the spot. Head to Settings (Windows + I) > Apps > Default apps > Choose default app by file type.

Cipher

Deleting files on a mechanical hard drive doesn't really delete them at all. Instead, it marks the files as no longer accessible and the space they took become free. The files remain recoverable until the system overwrites them with new data, which can take some time.

The cipher command, however, lets you wipe a directory on an NTFS-formatted volume by writing random data to it. To wipe your C drive, for example, you'd use the cipher /w:d command, which will wipe free space on the drive. The command does not overwrite undeleted data, so you will not wipe out the files you need by running this command.

When you run the cipher command by itself, it returns the encryption state of the current directory and the files it contains. Use cipher /e:<filename> to encrypt a file, cipher /c:<filename> to retrieve information about encrypted files, and cipher /d:<filename> to decrypt the selected file. Most of these commands are redundant with the Windows encryption tool BitLocker.

File Compare (fs) 

You can use fc command to identify differences in text between two files. It's particularly useful for writers and programmers trying to find small changes between two versions of a file. Simply type fc and then the directory path and file name of the two files you want to compare.

You can also extend the command in several ways. Typing /b compares only binary output, /c disregards the case of text in the comparison, and /l only compares ASCII text.

The following is an example of the File Compare:

fc /l "C:\Program Files (x86)\example1.doc" "C:\Program Files (x86)\example2.doc"

Ipconfig

This command relays the IP address that your computer is currently using. However, if you're behind a router (like most computers today), you'll instead receive the local network address of the router.

Still, ipconfig is useful because of its extensions. ipconfig /release followed by ipconfig /renew can force your Windows PC into asking for a new IP address, which is useful if your computer claims one isn't available. You can also use ipconfig /flushdns to refresh your DNS address. These commands are great if the Windows network troubleshooter chokes, which does happen on occasion.

Netstat

Entering the command netstat -an will provide you with a list of currently open ports and related IP addresses. This command will also tell you what state the port is in; listening, established, or closed.

This is a great command for when you're trying to troubleshoot devices connected to your PC or when you fear a Trojan infected your system and you're trying to locate a malicious connection.

Ping

Sometimes, you need to know whether or not packets are making it to a specific networked device. That's where ping comes in handy.

Typing ping followed by an IP address or web domain will send a series of test packets to the specified address.  example: ping destrotech.com, ping  217.182.198.230.  If they arrive and are returned, you know the device is capable of communicating with your PC; if it fails, you know that there's something blocking communication between the device and your computer. This can help you decide if the root of the issue is an improper configuration or a failure of network hardware such as cabling.

PathPing

This is a more advanced version of ping that's useful if there are multiple routers between your PC and the device you're testing. Like ping, you use this command by typing pathping followed by the IP address, but unlike ping, pathping also relays some information about the route the test packets take.

Tracert

The tracert command is similar to pathping. Once again, type tracert followed by the IP address or domain you'd like to trace. You'll receive information about each step in the route between your PC and the target. Unlike pathping, however, tracert also tracks how much time (in milliseconds) each hop between servers or devices takes.

Shutdown

This is, of course, redundant with the already easily accessed shutdown button, but what's not redundant is the shutdown /r /o command, which restarts your PC and launches the Advanced Start Options menu, which is where you can access Safe Mode and Windows recovery utilities. This is useful if you want to restart your computer for troubleshooting purposes.

System File Checker

System File Checker is an automatic scan and repair tool that focuses on Windows system files.

You will need to run the command prompt with administrator privileges and enter the command sfc /scannow. If SFC finds any corrupt or missing files, it will automatically replace them using cached copies kept by Windows for this purpose alone. The command can require a half-hour to run on older notebooks.

Chkdsk 

Windows automatically marks your drive for a diagnostic chkdsk scan when symptoms indicate that a local drive has bad sectors, lost clusters, or other logical or physical errors.

If you suspect your hard drive is failing, you can manually initiate a scan. The most basic command is chkdsk c:, which will immediately scan the C: drive, without a need to restart the computer. If you add parameters like /f, /r, /x, or /b, such as in chkdsk /f /r /x /b c:, chkdsk will also fix errors, recover data, dismount the drive, or clear the list of bad sectors, respectively. These actions require a reboot, as they can only run with Windows powered down.

Schtasks

Schtasks is your command prompt access to the Task Scheduler, one of many underrated Windows administrative tools. While you can use the GUI to manage your scheduled tasks, the command prompt lets you copy&paste complex commands to set up multiple similar tasks without having to click through various options. Ultimately, it's much easier to use, once you've committed key parameters to memory.

For example, you could schedule your computer to reboot at 11pm every Friday:

schtasks /create /sc weekly /d FRI /tn "auto reboot computer weekly" /st 23:00 /tr "shutdown -r -f -t 10"

Cls

Cluttered up your command prompt window trying out all the commands above? The Cls command cleans your screen up again.

SystemInfo

This command will give you a detailed configuration overview of your computer. The list covers your operating system and hardware. For example, you can look up the original Windows installation date, the last boot time, your BIOS version, total and available memory, installed hotfixes, network card configurations, and more.

Use systeminfo /s followed by the hostname of a computer on your local network, to remotely grab the information for that system. This may require additional syntax elements for the domain, user name, and password, like this:

systeminfo /s [host_name] /u [domain]\[user_name] /p [user_password