Operating Systems

Trojan horses disguise themselves as legitimate or useful software to trick users into installing them. Once executed, they provide unauthorized access or perform malicious actions. Unlike viruses, they don't self-replicate but rely on social engineering.

Segmentation divides memory into variable-sized segments, leading to external fragmentation when unused gaps develop between segments. Swapping moves processes in and out of memory, pure demand paging loads pages only when needed, and fixed partitions have internal fragmentation.

Buffer caches improve disk performance by reducing disk accesses - frequently used data stays in memory. They don't handle interrupts, increase main memory capacity, or speed up general memory reads.

The dispatcher is the component that actually moves tasks from ready state to running state by scheduling them into the processor. It doesn't put tasks in I/O wait, isn't necessarily simple, and can change priorities.

Command interpreters (shells) are typically the primary user interface for interacting with operating systems. They don't require fixed formats, aren't menu-driven, and SCL is unclear but irrelevant to the correct definition.

A semaphore initialized to 1 ensures mutual exclusion - only one process can enter the critical section at a time. Value 0 would block all processes, while 8 or 16 would allow multiple concurrent entries.

A loader is a system program that loads executable programs from secondary storage into main memory and prepares them for execution. It allocates memory, relocates addresses, and initializes the program. Assemblers convert assembly code to machine code, linkers combine object files, and compilers translate high-level code to machine code.