The system configuration defines limits for certain MS-DOS resources and affects how much memory MS-DOS allocates to support these resources. The system configuration is set by commands in the MS-DOS configuration file, CONFIG.SYS. For programs with special needs, the user may need to add or modify one or more commands.
The following is a list of the configuration commands that may affect programs:
| Command | Comments |
| buffers | Sets the number of file buffers. More buffers can improve performance of programs that repeatedly open the same files or files in the same directories. Disk-caching programs, such as SMARTDrive, can also be used to speed access to files. |
| country | Sets the current country code. Programs that modify their output for different national markets should require the user to specify this command. |
| device | Installs a device driver. Programs that require device drivers must direct the user to supply an appropriate device or devicehigh command. |
| dos | Specifies whether MS-DOS is to relocate to the high memory area (HMA) and whether MS-DOS is to make upper memory blocks (UMBs) available to programs. Programs that either need more memory or can improve performance with additional memory should recommend this command. |
| fcbs | Sets the number of file control blocks (FCBs) a program can have open at one time. This setting is useful for programs that use FCBs. |
| files | Sets the maximum number of files that may be open at any one time. Programs that open many files or run child programs that open their own files should direct the user to set an appropriate maximum. |
| install | Loads a terminate-and-stay-resident program (a TSR). A program that must run as a TSR can recommend that the user install it by using this command. |
| lastdrive | Sets the maximum number of drives MS-DOS permits access to. Programs that connect to many network drives may need to direct the user to set an appropriate maximum. |
| stacks | Specifies the size and number of stacks used for hardware interrupts. This command is useful for hardware support programs that install interrupt service routines for selected interrupts, especially if the service routines require large amounts of stack space. |
For more information about these commands, see the Microsoft MS-DOS User's Guide and Reference.