Operating Systems

Step 1: Understand the layers of MS-DOS.
The layers of the MS-DOS operating system can be arranged in the following order starting from the innermost to the outermost: - **(A) ROM BIOS Device Drivers**: These are the lowest level of the system and interact directly with the hardware. They are part of the ROM (Read-Only Memory).
- **(C) MS-DOS Device Drivers**: These drivers are used to control the system's devices and interact with the hardware through the ROM BIOS.
- **(B) Resident System Program**: This program is loaded into memory during the boot process and manages system functions like file handling, memory management, etc.
- **(D) Application Program**: This is the highest layer and refers to user programs or software that interact with the operating system to perform tasks.

Step 2: Conclusion.
The correct order of layers is **(A), (C), (B), (D)**.