While running MS DOS on a personal computer, which command is used to duplicate the entire contents of one diskette onto another diskette?

Introduction / Context:
Early personal computers running MS DOS used floppy diskettes for program distribution and data storage. Users often needed to make an exact copy of one diskette onto another. MS DOS provided specific commands for copying files, copying entire diskettes and formatting disks. Exam questions test whether you remember which command performs which function.

Given Data / Assumptions:

We are working with MS DOS command line utilities.
The goal is to duplicate the entire diskette, including files and directory structure.
We want a command that operates at the disk level, not just on individual files.
The options list common DOS commands.

Concept / Approach:
The DISKCOPY command in MS DOS is designed specifically to copy the contents of one floppy disk directly to another. It copies sector by sector, creating a complete duplicate. The COPY and XCOPY commands work on files and directories rather than on raw disks. The FORMAT command prepares a disk for use by creating a file system structure and optionally erasing existing data, but it does not copy data from another disk.

Step-by-Step Solution:
Step 1: Recall that DISKCOPY syntax typically looks like DISKCOPY A: B:, meaning copy from drive A to drive B. Step 2: DISKCOPY reads sectors from the source diskette and writes them to the target diskette, producing a clone of the original. Step 3: COPY and XCOPY commands require file or directory names and are used to copy selected files, not to clone entire diskettes at the sector level. Step 4: FORMAT initializes a disk and removes previous contents but does not copy anything from another disk. Step 5: Therefore, the correct choice for duplicating an entire diskette is DISKCOPY.

Verification / Alternative check:
MS DOS manuals and help screens describe DISKCOPY as the command used to copy the complete contents of one floppy disk to another, including boot sectors, directory entries and files. The documentation for COPY and XCOPY focuses on file copying, often with wildcards and directory trees. FORMAT is documented as creating a new file system and optionally checking the disk for errors.

Why Other Options Are Wrong:
COPY is limited to copying files and cannot create an exact low level clone of an entire diskette in one step.
XCOPY is an extended file copy command for directory trees but still works at the file system level, not at the raw disk level.
FORMAT erases or initializes a disk and does not copy data from another diskette.

Common Pitfalls:
Users sometimes try to use COPY with wildcards such as COPY A:*.* B: and believe they have created a full duplicate. This may miss hidden or system files and does not replicate boot sectors. DISKCOPY is required for a true sector by sector duplication. Remembering the difference is useful when dealing with bootable disks and exact backups.

Final Answer:
The MS DOS command used to duplicate an entire diskette is DISKCOPY, which copies the source disk sector by sector to the target disk.