Examples of Operating Systems
Windows, MacOS, iOS, Linux
What are the five major functions of an operating system?
- User interface
- Peripheral management and drivers
- File Management
- Memory management and multitasking
- User management
What is a user interface?
OS provided means to interact with the computer, often through buttons, keyboard or mice.
What types of user interface is there?
- Command line interface (purely text)
- Graphical User Interface (GUI)
- WIMP interface (eg Windows) -> Windows, Icons, Menus, Pointers
What are peripheral devices and examples?
Devices connected externally to the CPU including printers, keyboards and monitors. Users communicate with the device via the OS.
What is a buffer used for?
To compensate for the difference in speed between the CPU and the device
What does the OS allow the user to do in terms of file management?
Files can be created, deleted, moved, saved, copied or allocated to folders. Can search for files, restore deleted files, free up space for new files and prevent conflicts when two users attempt to modify the same file at the same time. Also manages access rights to individual files.
What does the OS do in terms of memory management?
The OS moves programs and files in and out of memory (from the hard drive or from virtual memory) to process tasks as required.
What is multi-tasking?
Switching quickly between tasks
What does the OS do in terms of user management?
Provides different users with an account with their own user name and password. Each user can be granted different levels of access depending on their needs and levels of security. OS can also monitor login activity and log out users after set periods of inactivity.
What are common utility software?
- Defragmentation software
- Encryption software
- Data compression software
Why are files fragmented?
Files are stored on the hard disk in blocks. As different size files are added and deleted over time, gaps appear which may not fit all of the next file to be stored. Files therefore become fragmented in order to fit them in.
What is the disadvantage of fragmented files?
Reading and storing the file is made much slower
What is the advantage of defragmentation utility?
Avoids fragmented files, new files can be saved in one place, speed up computer’s file retrieval and storage times - speeds up read and write access
What does a defragmentation software do?
Moves file around and store them individual files in neighbouring blocks, avoiding fragmented files.
What does an encryption software do?
Encrypts or decrypts files or folders held on a computer, transmitted across a network or transferred to external devices such as a USB key. Uses an algorithm and key to transform plaintext into ciphertext, scrambling data to increase security of data packets transfer. To decode the original information (plaintext), both the algorithm and the key is necessary to know.
What does data compression software do?
Uses an algorithm to resave the data into an existing file using less storage space than the original. Uses lossy or lifeless.
Example of compression software
WinZip
Advantages of compression in different situations
Enables larger files to fit within email attachment limits, reduces the data transfer volumes to meet ISP limits, and saves space on a local disk. Allows multiple original files to be saved as one single file, which is helpful for email and distribution.
What is the main purpose of the operating system?
To manage the computer’s resources
