1.2.1e+f+g+h – Systems Software - Done

Distributed operating systems are designed to run the same task over multiple computers. e.g. SETI (Search for Extraterrestrial Intelligence)

Embedded operating systems have a restricted set of operations for a dedicated function. This is so they can run with maximum efficiency, consuming less power than other operating systems. They store firmware, that doesn’t need to be updated, in the ROM, so that access is faster, or can use it as primary storage so programs don’t need to be loaded into memory. This means that the machine is read only. e.g. Washing machine

Multi-tasking operating systems are optimised to deal with multiple processes simultaneously and can run multiple programs at the same time. E.g. Personal computer

Multi-user operating systems allow multiple users to access the computer at the same time. E.g. A Unix System where multiple remote users have access to the shell prompt at the same time

Real-time operating systems are optimised to handle and respond to input immediately, so are used in ‘mission critical’ systems. E.g. Aircraft control

The BIOS is stored in ROM. It tests hardware and boots up the operating system.

The BIOS contains the computer start up instructions. Firstly, it loads the settings. It then carries out a POST (Power-On-Self-Test) check and reports errors. The BIOS then determines the drive on which the OS is stored. It loads the bootstrap.

A device driver is software that allows the operating system to communicate with hardware. E.g. printer driver, webcam driver

The driver is required to translate the operating system’s instructions into commands that the device can understand and vice versa. Otherwise, the OS wouldn’t know how to control the hardware. They also enable devices to work with different versions of an operating system. Drivers are specific to the operating system installed on the device, but different drivers must be used for different device types.

A software-based computer that runs an operating system and applications like a real computer, using part of the host computer’s hardware. E.g. An emulator

• For testing software • To run multiple operating systems • Safely handling untrusted files • To run intermediate code • To run a software driven machine inside a physical machine

• Reduced hardware requirements means reduced hardware costs • If the virtual machine is infected by malware the rest of the system isn’t affected • They allow for efficient use of computing resources as data can be added to/removed allowing computers to be allocated resources dynamically based on their needs and status

• They can cause network overload if the network does not have sufficiently good bandwidth • They can create process lag if lots of large processes run at the same time • If a virtual machine crashes the user is unable to reset it whereas they can physically reboot on a local machine. • Purchasing virtual machine software and storage space can be more costly than installing physical servers for each application • Performance overhead due to shared resources • If host security is compromised, all virtual machines are at risk • Creating too many Virtual machines you don’t actively use can lead to server sprawl (underutilised virtual machines taking up more space and consuming more resources than can be justified by their workload)

Intermediate code is code halfway between machine code and object code. It is independent of the processor architecture, so it can be used across different machines and operating systems. It is translated by a virtual machine running on a target device, which then translates it into specific machine code. E.g. Java / Java Virtual Machine

• Code is highly portable between devices • Saves the time and money of having to purchase multiple devices solely for testing

• Can be slower compared to running low-level code on the device it was designed for

A cheap, small, low-performance computer that is accessed in the usual way with a keyboard and mouse, but in which all the processing takes place on a virtual machine on a server. They may not be compatible with the same peripherals as general-purpose computers.