DOS II Final Examination — 2026/2027
DOS II DISK OPERATING SYSTEM
FINAL EXAMINATION — 2026/2027
75 Questions • Multiple-Choice, Command-Syntax, and Scenario-Based
Testing Time: 90–120 minutes
Passing Score: 75–80%
Study Guide Format: Questions with Correct Answers and Rationales
Domain 1: DOS Architecture & Boot Process
1. Which DOS file is responsible for loading the system kernel during the boot process?
A. COMMAND.COM
B. IO.SYS
C. AUTOEXEC.BAT
D. CONFIG.SYS
Correct Answer: B. IO.SYS
Rationale: IO.SYS is the first file loaded by the BIOS bootstrap routine after the MBR locates the
active partition. It contains the DOS BIOS which initializes hardware and loads MSDOS.SYS.
COMMAND.COM is loaded last as the command interpreter.
2. What is the correct boot sequence of DOS system files?
A. COMMAND.COM → IO.SYS → MSDOS.SYS
B. IO.SYS → MSDOS.SYS → CONFIG.SYS → AUTOEXEC.BAT → COMMAND.COM
C. AUTOEXEC.BAT → CONFIG.SYS → IO.SYS → MSDOS.SYS
D. MSDOS.SYS → IO.SYS → COMMAND.COM → CONFIG.SYS
Correct Answer: B. IO.SYS → MSDOS.SYS → CONFIG.SYS → AUTOEXEC.BAT →
COMMAND.COM
Rationale: After the BIOS POST and MBR bootstrap, IO.SYS is loaded first. It initializes
hardware and loads MSDOS.SYS (the kernel). Then CONFIG.SYS is processed for device drivers
and settings, followed by AUTOEXEC.BAT for user configurations, and finally COMMAND.COM
is reloaded as the command shell.
3. What does the Master Boot Record (MBR) contain?
A. The BIOS firmware and POST routines
B. The bootstrap code, partition table, and boot signature (55AAh)
C. IO.SYS and MSDOS.SYS file headers
D. CONFIG.SYS and AUTOEXEC.BAT configurations
Correct Answer: B. The bootstrap code, partition table, and boot signature (55AAh)
Rationale: The MBR is located at cylinder 0, head 0, sector 1 and contains three components: the
bootstrap loader code (first 446 bytes), the partition table (64 bytes describing up to 4 primary
partitions), and the boot signature (2 bytes: 55h AAh).
4. Which file contains the DOS kernel that provides file management, memory
management, and process control?
A. IO.SYS
B. COMMAND.COM
C. MSDOS.SYS
D. IBMBIO.COM
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, DOS II Final Examination — 2026/2027
Correct Answer: C. MSDOS.SYS
Rationale: MSDOS.SYS is the DOS kernel. It provides the core operating system services
including file allocation table management, memory allocation, process scheduling, and the
DOS API (interrupt 21h). IO.SYS provides the hardware-specific BIOS interface.
5. During the DOS boot process, which configuration file is processed FIRST?
A. AUTOEXEC.BAT
B. CONFIG.SYS
C. COMMAND.COM
D. MSDOS.SYS
Correct Answer: B. CONFIG.SYS
Rationale: CONFIG.SYS is processed before AUTOEXEC.BAT. CONFIG.SYS loads device drivers
(via DEVICE= and DEVICEHIGH=), sets system parameters (BUFFERS, FILES, STACKS,
LASTDRIVE), and configures memory managers. AUTOEXEC.BAT is executed afterward for
environment setup and application initialization.
6. What is the role of COMMAND.COM during DOS startup?
A. It initializes hardware devices and loads drivers
B. It manages disk partitions and file allocation tables
C. It serves as the command interpreter, providing the user interface and executing batch files
D. It allocates extended memory above 1 MB
Correct Answer: C. It serves as the command interpreter, providing the user
interface and executing batch files
Rationale: COMMAND.COM is the DOS command interpreter (shell). It reads user input,
executes internal commands (DIR, COPY, DEL, etc.), processes batch files (.BAT), and provides
the C:\> prompt. It has a resident portion and a transient portion that can be overwritten by
applications.
7. In PC DOS, what are the equivalent names for the DOS system files IO.SYS and
MSDOS.SYS?
A. IBMBIO.SYS and IBMDOS.SYS
B. COMMAND.COM and CONFIG.SYS
C. BIOS.SYS and KERNEL.SYS
D. BOOT.SYS and KERNEL.SYS
Correct Answer: A. IBMBIO.SYS and IBMDOS.SYS
Rationale: PC DOS (from IBM) uses IBMBIO.SYS (equivalent to IO.SYS in MS-DOS) and
IBMDOS.SYS (equivalent to MSDOS.SYS). Both sets provide the same functionality:
IBMBIO.SYS/IO.SYS handles hardware I/O, and IBMDOS.SYS/MSDOS.SYS provides the kernel
services.
8. Where is the bootstrap program that starts the DOS boot process located?
A. In the ROM BIOS chip
B. In the first sector of the active partition (Volume Boot Record)
C. In COMMAND.COM
D. In the last sector of the hard drive
Correct Answer: B. In the first sector of the active partition (Volume Boot Record)
Rationale: After the BIOS loads the MBR from the first sector of the physical disk, the MBR
bootstrap code reads the partition table to find the active partition and loads the Volume Boot
Record (VBR) from that partition's first sector. The VBR then locates and loads IO.SYS.
Domain 2: File System Fundamentals
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, DOS II Final Examination — 2026/2027
9. What is the purpose of the File Allocation Table (FAT) in a DOS file system?
A. It stores the actual file data on disk
B. It maintains a linked list of cluster numbers indicating how file data is distributed across the
disk
C. It holds the directory structure and folder hierarchy
D. It records file permissions and security attributes
Correct Answer: B. It maintains a linked list of cluster numbers indicating how file
data is distributed across the disk
Rationale: The FAT is a table that maps each cluster on the disk. For each cluster, the FAT entry
indicates whether the cluster is free (0000h), bad (FFF7h), the last cluster of a file (FFF8-
FFFFh), or the cluster number of the next cluster in the chain. This linked-list structure allows
non-contiguous file storage.
10. What is the maximum number of entries in the root directory of a FAT12/FAT16 file
system on a hard disk?
A. 112 entries
B. 224 entries
C. 512 entries
D. Unlimited entries
Correct Answer: C. 512 entries
Rationale: On hard disks formatted with FAT12 or FAT16, the root directory is a fixed-size area
that typically holds 512 entries. Each 32-byte directory entry can describe a file or subdirectory.
Floppy disks have 112 or 224 root entries depending on capacity. Subdirectories created within
the root do not have this fixed limit.
11. What are the four standard DOS file attributes?
A. Read-Only, Hidden, System, Archive
B. Execute, Write, Delete, Archive
C. Read, Write, Execute, Hidden
D. Public, Private, System, Archive
Correct Answer: A. Read-Only, Hidden, System, Archive
Rationale: DOS files have four attributes stored in a single byte within the directory entry:
Read-Only (01h) prevents file modification, Hidden (02h) hides the file from normal DIR
listings, System (04h) marks system files, and Archive (20h) indicates whether the file has been
modified since last backup.
12. In a FAT16 file system, how many bytes does each FAT entry occupy?
A. 12 bits (1.5 bytes)
B. 16 bits (2 bytes)
C. 32 bits (4 bytes)
D. 8 bits (1 byte)
Correct Answer: B. 16 bits (2 bytes)
Rationale: FAT16 uses 16-bit (2-byte) entries in the File Allocation Table, allowing up to 65,536
clusters. This limits the partition size depending on the cluster size: with 32KB clusters, the
maximum partition is 2 GB. FAT12 uses 12-bit entries (floppies) and FAT32 uses 32-bit entries.
13. How does VFAT (Virtual FAT) support Long File Names (LFNs)?
A. It increases the directory entry size from 32 to 64 bytes
B. It creates additional 32-byte directory entries that store the long name in Unicode characters
C. It stores the long name in a separate hidden file called LFNSYS.DAT
D. It compresses filenames to fit within the 8.3 format
Correct Answer: B. It creates additional 32-byte directory entries that store the long
name in Unicode characters
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DOS II DISK OPERATING SYSTEM
FINAL EXAMINATION — 2026/2027
75 Questions • Multiple-Choice, Command-Syntax, and Scenario-Based
Testing Time: 90–120 minutes
Passing Score: 75–80%
Study Guide Format: Questions with Correct Answers and Rationales
Domain 1: DOS Architecture & Boot Process
1. Which DOS file is responsible for loading the system kernel during the boot process?
A. COMMAND.COM
B. IO.SYS
C. AUTOEXEC.BAT
D. CONFIG.SYS
Correct Answer: B. IO.SYS
Rationale: IO.SYS is the first file loaded by the BIOS bootstrap routine after the MBR locates the
active partition. It contains the DOS BIOS which initializes hardware and loads MSDOS.SYS.
COMMAND.COM is loaded last as the command interpreter.
2. What is the correct boot sequence of DOS system files?
A. COMMAND.COM → IO.SYS → MSDOS.SYS
B. IO.SYS → MSDOS.SYS → CONFIG.SYS → AUTOEXEC.BAT → COMMAND.COM
C. AUTOEXEC.BAT → CONFIG.SYS → IO.SYS → MSDOS.SYS
D. MSDOS.SYS → IO.SYS → COMMAND.COM → CONFIG.SYS
Correct Answer: B. IO.SYS → MSDOS.SYS → CONFIG.SYS → AUTOEXEC.BAT →
COMMAND.COM
Rationale: After the BIOS POST and MBR bootstrap, IO.SYS is loaded first. It initializes
hardware and loads MSDOS.SYS (the kernel). Then CONFIG.SYS is processed for device drivers
and settings, followed by AUTOEXEC.BAT for user configurations, and finally COMMAND.COM
is reloaded as the command shell.
3. What does the Master Boot Record (MBR) contain?
A. The BIOS firmware and POST routines
B. The bootstrap code, partition table, and boot signature (55AAh)
C. IO.SYS and MSDOS.SYS file headers
D. CONFIG.SYS and AUTOEXEC.BAT configurations
Correct Answer: B. The bootstrap code, partition table, and boot signature (55AAh)
Rationale: The MBR is located at cylinder 0, head 0, sector 1 and contains three components: the
bootstrap loader code (first 446 bytes), the partition table (64 bytes describing up to 4 primary
partitions), and the boot signature (2 bytes: 55h AAh).
4. Which file contains the DOS kernel that provides file management, memory
management, and process control?
A. IO.SYS
B. COMMAND.COM
C. MSDOS.SYS
D. IBMBIO.COM
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, DOS II Final Examination — 2026/2027
Correct Answer: C. MSDOS.SYS
Rationale: MSDOS.SYS is the DOS kernel. It provides the core operating system services
including file allocation table management, memory allocation, process scheduling, and the
DOS API (interrupt 21h). IO.SYS provides the hardware-specific BIOS interface.
5. During the DOS boot process, which configuration file is processed FIRST?
A. AUTOEXEC.BAT
B. CONFIG.SYS
C. COMMAND.COM
D. MSDOS.SYS
Correct Answer: B. CONFIG.SYS
Rationale: CONFIG.SYS is processed before AUTOEXEC.BAT. CONFIG.SYS loads device drivers
(via DEVICE= and DEVICEHIGH=), sets system parameters (BUFFERS, FILES, STACKS,
LASTDRIVE), and configures memory managers. AUTOEXEC.BAT is executed afterward for
environment setup and application initialization.
6. What is the role of COMMAND.COM during DOS startup?
A. It initializes hardware devices and loads drivers
B. It manages disk partitions and file allocation tables
C. It serves as the command interpreter, providing the user interface and executing batch files
D. It allocates extended memory above 1 MB
Correct Answer: C. It serves as the command interpreter, providing the user
interface and executing batch files
Rationale: COMMAND.COM is the DOS command interpreter (shell). It reads user input,
executes internal commands (DIR, COPY, DEL, etc.), processes batch files (.BAT), and provides
the C:\> prompt. It has a resident portion and a transient portion that can be overwritten by
applications.
7. In PC DOS, what are the equivalent names for the DOS system files IO.SYS and
MSDOS.SYS?
A. IBMBIO.SYS and IBMDOS.SYS
B. COMMAND.COM and CONFIG.SYS
C. BIOS.SYS and KERNEL.SYS
D. BOOT.SYS and KERNEL.SYS
Correct Answer: A. IBMBIO.SYS and IBMDOS.SYS
Rationale: PC DOS (from IBM) uses IBMBIO.SYS (equivalent to IO.SYS in MS-DOS) and
IBMDOS.SYS (equivalent to MSDOS.SYS). Both sets provide the same functionality:
IBMBIO.SYS/IO.SYS handles hardware I/O, and IBMDOS.SYS/MSDOS.SYS provides the kernel
services.
8. Where is the bootstrap program that starts the DOS boot process located?
A. In the ROM BIOS chip
B. In the first sector of the active partition (Volume Boot Record)
C. In COMMAND.COM
D. In the last sector of the hard drive
Correct Answer: B. In the first sector of the active partition (Volume Boot Record)
Rationale: After the BIOS loads the MBR from the first sector of the physical disk, the MBR
bootstrap code reads the partition table to find the active partition and loads the Volume Boot
Record (VBR) from that partition's first sector. The VBR then locates and loads IO.SYS.
Domain 2: File System Fundamentals
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, DOS II Final Examination — 2026/2027
9. What is the purpose of the File Allocation Table (FAT) in a DOS file system?
A. It stores the actual file data on disk
B. It maintains a linked list of cluster numbers indicating how file data is distributed across the
disk
C. It holds the directory structure and folder hierarchy
D. It records file permissions and security attributes
Correct Answer: B. It maintains a linked list of cluster numbers indicating how file
data is distributed across the disk
Rationale: The FAT is a table that maps each cluster on the disk. For each cluster, the FAT entry
indicates whether the cluster is free (0000h), bad (FFF7h), the last cluster of a file (FFF8-
FFFFh), or the cluster number of the next cluster in the chain. This linked-list structure allows
non-contiguous file storage.
10. What is the maximum number of entries in the root directory of a FAT12/FAT16 file
system on a hard disk?
A. 112 entries
B. 224 entries
C. 512 entries
D. Unlimited entries
Correct Answer: C. 512 entries
Rationale: On hard disks formatted with FAT12 or FAT16, the root directory is a fixed-size area
that typically holds 512 entries. Each 32-byte directory entry can describe a file or subdirectory.
Floppy disks have 112 or 224 root entries depending on capacity. Subdirectories created within
the root do not have this fixed limit.
11. What are the four standard DOS file attributes?
A. Read-Only, Hidden, System, Archive
B. Execute, Write, Delete, Archive
C. Read, Write, Execute, Hidden
D. Public, Private, System, Archive
Correct Answer: A. Read-Only, Hidden, System, Archive
Rationale: DOS files have four attributes stored in a single byte within the directory entry:
Read-Only (01h) prevents file modification, Hidden (02h) hides the file from normal DIR
listings, System (04h) marks system files, and Archive (20h) indicates whether the file has been
modified since last backup.
12. In a FAT16 file system, how many bytes does each FAT entry occupy?
A. 12 bits (1.5 bytes)
B. 16 bits (2 bytes)
C. 32 bits (4 bytes)
D. 8 bits (1 byte)
Correct Answer: B. 16 bits (2 bytes)
Rationale: FAT16 uses 16-bit (2-byte) entries in the File Allocation Table, allowing up to 65,536
clusters. This limits the partition size depending on the cluster size: with 32KB clusters, the
maximum partition is 2 GB. FAT12 uses 12-bit entries (floppies) and FAT32 uses 32-bit entries.
13. How does VFAT (Virtual FAT) support Long File Names (LFNs)?
A. It increases the directory entry size from 32 to 64 bytes
B. It creates additional 32-byte directory entries that store the long name in Unicode characters
C. It stores the long name in a separate hidden file called LFNSYS.DAT
D. It compresses filenames to fit within the 8.3 format
Correct Answer: B. It creates additional 32-byte directory entries that store the long
name in Unicode characters
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