Software
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When are interrupts checked for
at the end of each FDE cycle
Uses of virtual machines
• used on networks to avoid redundant processors • translating code (Java) • running different operating systems
boot up process of a computer
• POST is run • clears anything in the registers • loads the address of the first instruction of the boot program into the PC • the boot program checks for start-up instructions on the BIOS • The OS kernel is loaded
Uses of Embedded operating systems
Washing machines, vending machines, car engine systems, traffic lights, pay and display machines
Uses of Multi-tasking operating systems
desktops and smart phones
Uses of real-time operating systems
Airline control, theatre bookings, heart monitors, production lines, radar systems
Uses of Multi-user operating systems
schools and offices
Use of distributed operating systems
Data centres, large companies, weather/financial modelling, data mining trend finding
functions of an OS (8)
• Provides a user interface • manages security • provides a platform for utilities/applications • manages external devices • managing the processor/scheduling • managing memory • provides a platform for networking • managing hardware
How does Java use virtual machine?
the virtual machine execute intermediate code (Java Byte code)
Device drivers are…
hardware dependent and OS specific
Multi-level feedback queue
uses multiple queues based of the priority of the process.
Non pre-emptive algorithms
• First come first serve - shortest job first
Pre-emptive algorithms
• Round Robin • Shortest Remaining Time • Multi-level feedback queue
Pre-emptive
Once a process has entered the running state it can be stopped
Aims of scheduling
• to provide an acceptable response time to all users • To maximise the time the CPU is usefully engaged • To ensure fairness on a multi-user system
What happens if an interrupt is detected?
• the contents of all the registers are pushed onto a stack • The interrupt service routine is run • Once complete the values of the registers are popped off the stack back into the registers
What does an OS provide?(4)
• User interface • Memory Management • Interrupt handling • Processor scheduling
What loads the OS into RAM
the bootloader
Library Programs (System Software)
contains useful functions that are frequently used by programs. Simplifies the process of application development.
Operating system (System software)
software that allows the user to control the computer with ease. It provides a virtual machine hiding the true complexity of the computer from the user and manages and controls access to the computer’s resources.
examples of system software
Operating system, Utility Program, Library Program, Translators.
system software
operates, controls and maintain the computer and its components.
Hardware
the physical components of the computer system.