the need for and purpose of operating systems Flashcards
operating system
An operating system controls the computer’s software and loads the instructions. Acts as a platform for applications to run.
what do operating systems provide
The operating system manages all of the software and hardware in a computer and performs tasks such as:
* -Memory management
* - Resource management eg. scheduling
* - File management
* - Input/ Output management
* - Interrupt management
* - Utility software
* - Security
* - User interface
examples of operating systems
linux, windows, android, macOS
what is meant by memory management
Programs and their data need to be loaded into RAM. The Operating System must manage the allocation of RAM to the different programs. There may not be sufficient RAM for all desired
processes to be completely loaded into RAM at once
What is paging
Paging is when memory is split up into equal-sized sections known as pages. These can then be swapped between main memory and the hard disk as needed.
what is segmentation
Segmentation is the splitting up of memory into logical sized divisions, known as segments, which vary in size. These represent the structure and logical flow of the program.
what is a Page table
A page table maps between the logical memory locations and the physical memory locations.
Logical address = A virtual address generated by the cpu while a program is running
virtual memory
Virtual memory uses a section of the hard drive to act as RAM when the space in main
memory is insufficient to store programs being used. Sections of programs not currently being used are temporarily moved into virtual memory through paging, freeing up memory for other programs in RAM.
disk thrashing
when the computer ‘freezes’ due to pages being swapped too frequently between the hard disk and main memory.
This issue becomes progressively worse as virtual memory is filled up. Buying more ram can reduce disk thrashing.
