Operating Systems Flashcards

Flashcards for Operating Systems lecture review.

What is an Operating System (OS)?

A program that acts as an intermediary between users' programs and the computer hardware, managing the hardware.

What are the two modes of operation in modern computers?

User mode and kernel mode.

What is an interrupt?

A signal to the processor emitted by hardware or software indicating an event that needs immediate attention.

Where is the bootstrap program typically stored?

ROM or EEPROM, generally known as firmware / BIOS / UEFI

What does the cron daemon do?

Executes scheduled tasks automatically.

What software is between the OS and the hardware?

The device driver.

What hardware is between the CPU and the device?

The device controller.

What is DMA (Direct Memory Access)?

Allows hardware devices to transfer data directly to or from main memory without involving the CPU.

What is hyperthreading?

Two virtual processors per core that can dynamically schedule instructions from both based on which execution units are free and which instructions are ready.

What is caching?

Copying instructions or data into a faster storage area to reduce access time.

What is the locality principle?

If a word is read or written k times in a short interval, the computer will need 1 reference to the slow memory and k-1 references to the fast memory.

What three factors are storage systems organized into a hierarchy based on?

Access speed, cost, and volatility.

What are volatile, fast memory types?

Registers, cache, main memory.

What are nonvolatile, slower memory types?

SSD, hard disk, optical disk, magnetic tape, cloud storage.

What is the formula for multiprocessor speedup?

Time to execute the program on a single processor / Time to execute program on N parallel processors

What is cache coherency?

Hardware mechanisms that ensure all CPUs access the most recent value, even if it is stored in another core's cache.

What is the execution time of a program on a multiprocessor platform according to Amdahl's Law?

(1 − f(1 − 1N ))T

What is a cache miss?

When the required data is not found in the cache.