DEC file icon

DEC File Extension

Declaration Format

What is DEC file?

DEC is a text-based developer file format used for such data as storing public variables or definitions. Data in DEC file are global in the sense that it can be accessed from anywhere in the programming project. DEC specification is defined in EDK II standard. DEC files are commonly used for developing UEFI software. UEFI is a software interface for implemented between operating system and firmware levels. UEFI specification provides an interface for developing device drivers independent of operating system. UEFI interface offers many advanced features, for example, mouse support.

Misunderstandings around DEC files

Many programmers treat DEC files as header files for various programming languages. Such practice is unsubstantiated and is not based on any programming methodology – it is more of an idiosyncrasy of Unix-developers.

Programs which support DEC file extension

The list that follows enumerates programs compatible with DEC files, divided into 2 categories based on operating system on which they are available. DEC files can be encountered on all system platforms, including mobile, yet there is no guarantee each will properly support such files.

Programs that support DEC file

Updated: 08/02/2023

How to open file with DEC extension?

Problems with accessing DEC may be due to various reasons. On the bright side, the most encountered issues pertaining to Declaration Format files aren’t complex. In most cases they can be addressed swiftly and effectively without assistance from a specialist. The list below will guide you through the process of addressing the encountered problem.

Step 1. Download and install ADL software

Install software to open DEC file The most common reason for such problems is the lack of proper applications that supports DEC files installed on the system. The solution is straightforward, just download and install ADL software. The full list of programs grouped by operating systems can be found above. The safest method of downloading ADL software installed is by going to developer’s website () and downloading the software using provided links.

Step 2. Verify the you have the latest version of ADL software

Update software that support file extension DECYou still cannot access DEC files although ADL software is installed on your system? Make sure that the software is up to date. Sometimes software developers introduce new formats in place of that already supports along with newer versions of their applications. The reason that ADL software cannot handle files with DEC may be that the software is outdated. All of the file formats that were handled just fine by the previous versions of given program should be also possible to open using ADL software.

Step 3. Associate Declaration Format files with ADL software

If the issue has not been solved in the previous step, you should associate DEC files with latest version of ADL software you have installed on your device. The method is quite simple and varies little across operating systems.

Associate software with DEC file on Windows

The procedure to change the default program in Windows

  • Choose the Open with entry from the file menu accessed by right-mouse clicking on the DEC file
  • Click Choose another app and then select More apps option
  • To finalize the process, select Look for another app on this PC entry and using the file explorer select the ADL software installation folder. Confirm by checking Always use this app to open DEC files box and clicking OK button.
Associate software with DEC file on Mac

The procedure to change the default program in Mac OS

  • Right-click the DEC file and select Information
  • Find the Open with option – click the title if its hidden
  • Select ADL software and click Change for all...
  • A message window should appear informing that This change will be applied to all files with DEC extension. By clicking Continue you confirm your selection.

Step 4. Check the DEC for errors

If you followed the instructions form the previous steps yet the issue is still not solved, you should verify the DEC file in question. Problems with opening the file may arise due to various reasons.

Check DEC file for viruses
1. The DEC may be infected with malware – make sure to scan it with an antivirus tool.

If the file is infected, the malware that resides in the DEC file hinders attempts to open it. Immediately scan the file using an antivirus tool or scan the whole system to ensure the whole system is safe. DEC file is infected with malware? Follow the steps suggested by your antivirus software.

2. Check whether the file is corrupted or damaged

If you obtained the problematic DEC file from a third party, ask them to supply you with another copy. The file might have been copied erroneously and the data lost integrity, which precludes from accessing the file. If the DEC file has been downloaded from the internet only partially, try to redownload it.

3. Verify whether your account has administrative rights

There is a possibility that the file in question can only be accessed by users with sufficient system privileges. Log out of your current account and log in to an account with sufficient access privileges. Then open the Declaration Format file.

4. Make sure that the system has sufficient resources to run ADL software

If the systems has insufficient resources to open DEC files, try closing all currently running applications and try again.

5. Verify that your operating system and drivers are up to date

Up-to-date system and drivers not only makes your computer more secure, but also may solve problems with Declaration Format file. It may be the case that the DEC files work properly with updated software that addresses some system bugs.

Conversion of a DEC file

File Conversions from DEC extension to a different format
File conversions from other format to DEC file
Do you want to help?

If you have additional information about the DEC file, we will be grateful if you share it with our users. To do this, use the form here and send us your information on DEC file.

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