What is an OS Flashcards
What is an Operating System
Software that manages computer hardware
- Manages application programs
- Acts as interface between user and hardware
What are the goals of an OS
- Convenience
- Efficiency
- Flexibility
What are the roles of an OS
- Resource Allocator
- Protection Mechanism
- Access to memory, storage, and I/O devices
What does the resource allocator do?
- Manage allocation of hw resources
- Concerned with fairness and efficiency
What does the protection mechanism do?
- Control execution of applications
- Prevents errors and improper use (IE reading data it shouldn’t access)
How does the OS provide access to memory, storage and I/O devices
Provides a consistent interface to hardware resources
What is the Kernel
- The “core” which interfaces with hardware.
- Drivers, HW management, Scheduling
What does an OS consist of?
- Kernel
- System programs and libraries
- Application programs
What is an example of an application program
Web browser, media player etc.
What does the System programs and libraries consist of?
Shell, GUI, system library (STDIO etc), utilities (ls, ps, cp…)
Give an example of a simple OS
Unit of work is a job (program and data). Each job is executed in serial
Has low CPU utilisation as the CPU cannot be kept busy due to IO.
What is multi-programming
Subset of jobs held in memory
Improves CPU utilisation.
CPU never idle so long as there are jobs to run (jobs in memory)
What is Time Sharing (Multi-tasking)?
CPU executes multiples jobs concurrently by switching between jobs quickly.
Users interact with running programs
Requires a low response time.
NB. Also allows multiple users to share a computer simultaneously
