Protecting files from modification in DOS: Which command makes the file CBT.EXE read-only to prevent subsequent changes?

Introduction / Context:
DOS file attributes control visibility and mutability. Setting the read-only attribute prevents edits and overwrites by many utilities. Technicians frequently toggle attributes to protect executables and configuration files.

Given Data / Assumptions:

• The file is CBT.EXE in the current directory.
• We want to prevent changes by setting read-only.
• DOS provides ATTRIB to manage file attributes (Read-only, Archive, System, Hidden).

Concept / Approach:

ATTRIB accepts +R to add the read-only attribute and -R to remove it. Once set, typical copy or editor operations will prompt or fail to overwrite unless attributes are cleared or forced by specialized tools.

Step-by-Step Solution:

Verification / Alternative check:

Issue ATTRIB CBT.EXE after the command to display current attributes and confirm the R flag is set. Attempting to overwrite will now typically produce an access denied or confirmation prompt.

Why Other Options Are Wrong:

• RENAME +r, COPY +r, MODE +r: These commands do not set attributes and the syntax is invalid in this context.
• None of the above: Incorrect because ATTRIB +R is correct.

Common Pitfalls:

Forgetting to remove the attribute when updating the file (use ATTRIB -R CBT.EXE). Also, note that some installers override attributes; verify after updates.

Final Answer:

ATTRIB +R CBT.EXE