DOS Boot Order and Startup Files On a classic DOS-based PC, which of the following lists shows the correct sequence of system startup batch/configuration files processed during the boot process?

Introduction / Context:
DOS systems follow a predictable boot sequence that initializes device drivers and sets environment variables before handing control to the command interpreter. Understanding this order helps troubleshoot boot issues and configure memory managers and drivers correctly.

Given Data / Assumptions:

• The machine boots to MS-DOS or DOS-compatible environment.
• Standard system files are present: IO.SYS (or IBMBIO.COM), MSDOS.SYS (or IBMDOS.COM), CONFIG.SYS, COMMAND.COM, and AUTOEXEC.BAT.
• No third-party boot managers alter the default flow.

Concept / Approach:
After the DOS system core is loaded, the operating system processes CONFIG.SYS to load device drivers and configure memory managers. Only after CONFIG.SYS completes does COMMAND.COM start and run AUTOEXEC.BAT to set environment variables, execute TSRs, and run startup utilities.

Step-by-Step Solution:
Power on → BIOS POST completes.Boot sector loads DOS system files (IO.SYS and MSDOS.SYS).DOS reads and executes directives in CONFIG.SYS (e.g., DEVICE=HIMEM.SYS, DEVICE=EMM386.EXE, FILES=, BUFFERS=).DOS loads COMMAND.COM (the command interpreter).COMMAND.COM automatically runs AUTOEXEC.BAT to configure PATH, PROMPT, mouse/keyboard TSRs, etc.

Verification / Alternative check:
Rename CONFIG.SYS temporarily and observe that device drivers are not loaded before AUTOEXEC.BAT runs. Conversely, editing CONFIG.SYS changes behavior before AUTOEXEC.BAT executes, confirming the order.

Why Other Options Are Wrong:
Option A and C contain misspelled or malformed filenames and reverse the proper order.Option D references CONFIG.BAT, which is not a standard DOS configuration file.Option E is wrong because a correct sequence appears in Option B.

Common Pitfalls:

• Confusing AUTOEXEC.BAT (batch file) with CONFIG.SYS (configuration directives).
• Assuming COMMAND.COM runs before CONFIG.SYS; in reality, COMMAND.COM is loaded after CONFIG.SYS processing.
• Forgetting that some DOS variants add extra options, but the core order remains.

Final Answer:
CONFIG.SYS, AUTOEXEC.BAT