1.2.1 - Systems Software

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What is system software?

What is system software?

A program that controls the hardware and applications of a computer.

Why do we need operating systems?

• Essential for managing the hardware and software resources of a computer system

• Provide an interface between the user and the hardware, allowing the user to interact with the system and run applications

What are the 8 main functions of an operating system?

Examples of operating systems: Windows, MacOS, Android, Linux, iOS

1. Memory management

2. Resource management

3. File management

4. Input/output management

5. Interrupt handling

6. Utility software

7. Security

8. Providing a user interface

Why do we need memory management?

• the allocation of memory allows separate processes to run at the same time

• it allows memory to be reallocated and shared when necessary

• protects different data and processes from each other, therefore provide security

What does memory management consist of?

Paging, segmentation and virtual memory

What is paging?

Partitions memory into fixed sixed physical divisions made to fit sections of memory

What is segmentation?

Partitions memory into variable sized logical divisions which hold complete sections of programs

What are the similarities between paging and segmentation?

Both:

• techniques try to optimise the use of RAM

• swap parts of programs used for virtual memory

• allow programs to be stored in memory non contiguously

• may cause disk thrashing when more time is spent swapping pages than processing (computer may ‘hang’)

What is 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 that are not currently in use are temporarily moved into virtual memory (through paging), freeing up memory for other programs in RAM

What’s a drawback of virtual memory?

Slower to access than physical memory (RAM), which degrades performance if overused

What is an interrupt?

A signal sent to the CPU generated by hardware or software, which causes a break in the execution of the current routine and transfers control to an interrupt service routine