Operating Systems
Manage computer hardware, users and the resources used by software
User interfaces
Provides a method for users to interact with a computer. E.g GUI (Graphical User Interface)
What is a GUI?
A visual way of interacting with a computer using items such as windows, icons, menus and pointers, used by most modern operating systems.
Menu- driven interface
Used by devices that have dedicated functions, e.g MP3 Player
Command Line Interface
Requires little processing and can save on the need for an expensive graphics card
Memory Management
To run a program, the computer must copy the program from storage into main memory
How does Memory Management work?
- Data used by the program is copied into main memory
- The Operating System keeps a record of where each program and its data are located
- The Operating System will make sure not to overwrite existing programs and data
Multi- Tasking
Where an operating system manages many tasks happening at the same time
Example of Multi- tasking
Having a web browser open whilst playing music and messaging friends
Many other background processes are also running
Operating system decides which process will next run on the CPU and for how long
Peripheral management and drivers
Operating system must manage getting inputs from and sending outputs to peripheral devices.
Name 3 peripherals
Mice, keyboard, printers
Device drivers
Program that controls peripheral devices such as printers, mice
How does device drivers work?
- Each device communicates with the operating system via it’s own driver
- Many device drivers come with an operating system. but if you buy a brand new type of device, it will be supplied with a driver, which will need to be installed
User management
Operating system is responsible for user logins and passwords which are stored in a file or database
Disk and file management
Hard disk in a computer is a storage peripheral
What does the operating system do?
- Manages where in the disk files are written
- Keeps track of where they are so they can be retrieved
- Makes sure no file overwrites another file
What is the file management carried out by and what are the feature available?
Carried out by Operating System.
Features available:
- Naming files
- Allocating files to folders
- Moving files
- Saving files
- Copying files
- Deleting files
Interrupts
Signals sent to CPU by external devices to indicate a event that needs immediate attention. They tell the CPU to suspend its current activities and execute appropriate instructions
Hardware interrupts
Generated by hardware devices- e.g printer out of paper
Software interrupts
Generated by programs- e.g divide-by-zero error will cause an error message to be displayed
What is Utility software?
Operating system controls and manages the computer system. Utility programs perform extra functionality and housekeeping tasks that keeps the computer running efficiently
Encryption software
Used to encode text so that it cannot be understood without knowing the key to decode it
Encryption software utilities are commonly used to what?
- Encrypt entire hard disks so that the data cannot be understood if the computer is stolen
- Encrypt files and folders on a portable disk- e.g USB removable storage
- Encrypt communication with websites
- Encrypt data in an organisation’s database- sensitive data- e.g passwords
Disk Defragmentation
When you save a large file it may not fit on the disk in consecutive memory locations. In order to read the file, the drive head will need to move to more locations. This makes it slower to access files and programs. Defragmenting the hard disk reorganises files so they are stored together. Read times are far faster and free space is in 1 place so new files do not need to be fragmented.
