- 2075 Asoj · 2+4 marks
DOS; monolithic and microkernel
Short answer
A distributed operating system manages multiple computers to appear as one. Monolithic kernels contain all services in a single kernel-mode program, fast but rigid. Microkernels minimize the kernel to IPC, scheduling, and memory, running other services as user-level servers, offering modularity and distribution support with message passing overhead.
What do you mean by DOS (Distributed Operating System)? Briefly explain the monolithic and microkernel architectures of operating system.
Distributed operating system (DOS)
A distributed operating system is an operating system that manages a collection of independent computers and makes them appear to the user as a single computer (uniprocessor view). It controls all the resources, schedules processes on any node, and provides transparency, a global file system and global IPC. Examples: Amoeba, Mach, Sprite.
Monolithic kernel
All OS services (process, memory, file and device management, networking) are in one large kernel running in kernel mode, communicating by direct procedure calls. It is fast but big, rigid and error-prone. Examples: UNIX, Linux.
Microkernel
The kernel contains only a minimal set (IPC, address spaces, thread scheduling, interrupt handling). Other services run as user-level servers and use message passing.
Monolithic: Microkernel:
[App] [App] [FS] [Net] [Mem mgr]
[ Big kernel: ---- message passing ----
FS,Net,MM,Drivers ] [ Microkernel: IPC,sched ]
Hardware Hardware
| Point | Monolithic kernel | Microkernel |
|---|---|---|
| Structure | All OS services (file system, memory, scheduling, drivers, networking) in one large kernel in kernel space | Only minimum functions (IPC, basic scheduling, low level memory, interrupts) in kernel |
| Other services | Part of kernel | Run as user-level servers |
| Communication | Direct procedure calls (fast) | Message passing between servers (slower) |
| Size | Large | Small |
| Reliability | A bug in one module can crash the system | A server failure does not crash the kernel |
| Flexibility, extensibility | Hard; needs recompilation | Easy; add/replace servers |
| Examples | UNIX, Linux, MS-DOS | Mach, Amoeba, Chorus, QNX |
✓ Answer checked by Claude Opus 5.5 (high effort)
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