Chapter 20 System software Flashcards
What starts the OS?
BIOS
What is a BIOS?
Is a code stored in ROM and starts a bootstrap program that loads the OS
What does an OS provide?
Provides facilities to have moe than one program stored in memory
Which are the two ways in which the purposes of the OS can be considered?
Internal viewpoint
External viewpoint
What is the internal viewpoint concerned about?
Concerns how the activities of the operating system are organised to best use the resources available
Concerns the facilities made available for system usage
What is the external viewpoint?
It is what the user sees
What does the multi-programing algorithm do?
Makes sure that only one program can acces the CPU at any given time but others are ready when the oppportunity arises and it is used when a single user is logged in
What is the time-sharing system designed for?
It is designed to have many users simultaneously logged in
Which are the three fundamental resources in a computer system?
the CPU
the memory
the I/O (input/output) system
What does the I/O system do?
Makes sure of what goes in and out of the:
CPU
Memory
Disk device driver
- Disk
Screen device driver
- Screen
Keyboard device driver
- Keyboard
Printer device driver
- PrinterWhat does the file system help with? Give one example.
Allowing the program to be created and run without the programmer being familiar with hot the processor functions
What does the API stand for?
Application Programming Interface
What does an API do?
Fulfils a specific function such as creating a screen icon
What is an API aim?
To provide portability for a program
Which are the two modes of operation that the operating system provides?
User mode
Kernl mode
What does the user more provide and contain?
The User Interface
What is kernel mode also known as?
Priviliged mode
What is the difference between kernel mode and user mode?
The difference between user mode and kernel is that kernal has access part of the memory and to certain system functions that user mode cannot access
What is a kernel?
Kernel is a computer program that is the core of a computer’s operating system, with complete control over everything in the system.
How does a layered structure look like?
Hardware interface
Kernel
Utilities
Application programs
User interfaceHow does the transition between the states of process scheduling happen?
A new process arrives in memory and a PCB is created; it changes to the ready state
A process is the ready state is given access to the CPU by the dispatcher; it changes to the running state
A process in the running state is halted by an interrupt; it returns to the ready state
A process in the running state cannot progress until some event has occured (I/O perhaps); it changes to hte waiting state (sometimes called the ‘suspended’ or ‘blocked’ state)
A process in the waiting state is notified that an event is completed; it returns to hte ready state
A process in the running state completes execution; it changes to the terminated state
What is a Process control block (PCB)?
Process control block (PCB) is a complex data structure containing all data relevant to the running of a process
In the scheduling process which are the five threads?
New Ready Waiting Running Terminated
When are interrupts implemented?
Used when a process in the running state makes a system call requiring an I/O operation and has to change to the waiting state
A scheduling algorithm decides to halt the process
