Section 4 Chapter 20 - Role of an Operating System Flashcards
Operating System
A program or set of programs that acts as a bridge between the user and the hardware
Where the OS is stored
In permanent storage usually the hard disk
The loader
A small program that is held in ROM that sends instructions to load the operating system into RAM
Functions of an operating system (7)
- Creation of a virtual machine
- Memory management
- Processor scheduling
- Backing store management
- Peripheral management
- Interrupt handling
- Provision of a user interface
Virtual machine
An instance where software is used to take on the function of the machine, including executing intermediate code or running an OS within another OS
What the operating system does in terms of memory management
Copies data that is not being used into virtual memory to free up RAM. The OS allocates memory to all the software that is running.
Virtual memory
Memory that is actually located in secondary storage but is automatically loaded into main memory when needed
Multi tasking (in terms of processor scheduling)
When a single processor appears to perform multiple tasks at the same time by carrying out a small section of each task in turn
Scheduler
An operating system module that decides which programs can use the cpu at what times in order for the highest efficiency
Objectives of the scheduler (3)
- Maximise throughput
- Be fair to all users on a multi-user system
- Provide acceptable response time to all users
- Ensure hardware resources are kept busy
Backing store management
A function of the operating system that keeps a directory of where files are stored and where there is free space. It also provides functionality to move, copy and delete files.
Peripheral management
A function of the operating system that handles input and output devices such as communicating with a printer
Interrupt handling
A function of the operating system that decides what to do when a software or peripheral program causes the operating system to stop processing its current list of instructions
Why can multi tasking take place
Because the processor can be interrupted
The role of the operating system
Hide the complexities of the hardware
