Application development tools and technology is constantly upgrading. Thus, seldom could you see in newer Windows operating system MS-DOS applications unless they are really important. Legacy dos based database applications are not upgraded in some cases due to missing source codes. The continuous Windows desktop operating system upgrades left out some software DOS applications unusable.

In-house software application running on MS-DOS causes some problem with newer OS like Windows XP or Windows 7. An error which I have encountered is the “Too many files open”. This is caused by the DOS application program opening up too many files.

Foxpro 2.6 DOS database application too many files open error

Solution to “Too many files open” error is to set the DOS configuration file called CONFIG.SYS. Changing settings to FILES=100 and BUFFERS=80 or higher values in CONFIG.SYS usually corrects the error. In MS-DOS and Windows 3.xx the CONFIG.SYS could be found in the root directory (eg. C:) where the system files boot.

Windows XP, Windows Vista or Windows 7 and other newer systems have CONFIG.SYS in system root directory C:, but it’s not being used. Making entries on the file doesn’t have any effect and you’ll end up still with the same error “Too many files open”.

The MS-DOS configuration has a new name CONFIG.NT and is located at Windowssystem32 directory. Entries such as FILES=100 and BUFFERS=100 in CONFIG.NT sets the right environment for the Foxpro 2.6 database application.

Windows XP CONFIG.NT foxpro 2.6 application configuration

After making the changes I restarted the machine for the environment to become active. When I run the Foxpro 2.6 DOS based application, the “Too many files open” error did not occur again.