Examples of operating systems
Microsoft Windows, macOS, iOS, Linux, Android
What is system software?
• System software is the software that provides a platform for other software to work
• There are different types, which are operating systems, utility programs and program translators
What are the functions of an operating system?
Operating systems manage computer hardware, users and the resources used by software
They are responsible for managing:
1. The user interface
2. Memory management
3. Multitasking
4. Peripheral management and drivers
5. User management
6. File management
What is the user interface?
• The user interface provides a method for users to
interact with a computer
• One type of interface is the graphical user interface (GUI)
What are the features of GUIs?
Desktop interface features:
• Pointers
• Windows
• Menus
• Icons
• Drag and drop
Smartphone and touch interfaces:
• No pointers in general as they cannot be seen under a finger
• Windows (for apps) generally take up the full screen
• Voice
• No menus -> icons
What is memory management?
Moves data from secondary storage to RAM and keeps
track of which data is where in RAM
• To run a program, the computer must copy the program from storage into main memory as this is where the CPU fetches the instructions from
• 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
Memory Management is key to multi-tasking
What is multi-tasking?
• Multi-tasking is where an operating system manages many tasks happening at the same time
• This may be having a web browser open whilst playing music and messaging friends
• Many other background processes also are running
• The operating system decides which process will next run on the CPU and for how long
• The CPU will allocate time (typically a very short amount of time) to each task in turn
• Gives the illusion to the user that multiple applications are running at the same time despite the CPU only being able to run a single process at a time
What is peripheral management and device drivers?
• The operating system must manage:
• Receiving input data from input devices
• Sending output data to peripheral devices
• Peripherals include Input and Output devices, and Storage devices, eg. mice, keyboard, printers, displays, USB sticks, etc
• All of these peripherals result in data being sent / received from them - the OS manages this process
How does peripheral management and device drivers work?
• A device driver is a program that enables the OS to
interact with peripheral devices such as printers, mice and displays
• Each device communicates with the OS via its own driver
• It translates instructions and data sent from the OS or the application into a form that the peripheral can understand, and therefore respond properly to those instructions
• 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 you will need to install
What is user management (login ids and passwords)
• The operating system maintains security via user logins
and passwords
• It will store all users and their passwords in a file or database
• It handles the administration of user accounts
What is user management (access rights)?
• The OS also manages the access rights assigned to
users:
• If a computer is used by more than one person, each user should be able to see only their own files
• Users and system administrators have different
levels of access rights
• Some users may be allowed to read files but not edit them
What is file management?
• File management is carried out by the operating system
• Manages where the files are stored on disk and makes sure no file overwrites another
• Provides the following functionality to users:
• Allocating files to folders
• Moving files
• Saving files
• Copying files
• Deleting files
• Search for files
Define utility software
• Operating systems manage computer hardware, users
and the resources used by software via core functions
such as memory management, file management, etc
• They also have additional systems software programs
called utility software
What is utility software?
Utility programs perform extra functionality and housekeeping tasks that keep computers running efficiently
• They are often packaged as part of the operating system
• Some utility programs, such as Anti-malware software, are bought as stand-alone software programs
Examples include:
1. Encryption software
2. Defragmentation software
3. Data compression
[4. Anti-malware software - not mentioned in spec]
What is encryption software?
• Encryption software is used to encode text so that it cannot be understood without knowing the key to decode it
• We’ve already seen encryption used for connections to
websites
• All the communication between the user and the website is encrypted
• Organisations may use encryption for a variety of uses:
• encryption of email attachments
• encryption of sensitive documents stored on the company’s servers
• encrypt all data being transferred to USB sticks
What is disk defragmentation?
• When you save a large file it may not fit on the hard disk in consecutive locations on the disk
• The file is referred to as ‘fragmented’
• In order to read the file, the read/write head will need to move to more locations
• This makes it far slower to access files and programs
• Defragmenting the hard disk reorganises files so they are stored together and the free space into one continuous block. Means:
• Fewer disk accesses are needed -> read times are far faster
• New files do not need to be fragmented as free space is in one continuous block -> fewer disk accesses to write the data, and also when comes to reading the file
Draw a diagram of disk defragmentation
N/a
What is data compression software?
• Utilities such as WinZip enable users to compress and
decompress files or folders
• If sending the files, it reduces the amount of data that is sent -> improving transmission and downloading speeds
• Compression may allow attachments to be sent via email that would otherwise have been larger than a file-size limit
• More data can be stored on backup media
• This reduces the amount of storage space needed for a disk
