Principles Of Operating Systems

Front 1

What does the core of the CPU contain?

Back 1

Control Unit, ALU, Generic registers, PC, Stack Pointer, Program Status Word (CCR), Cache memory.

Front 2

What are the two processor modes?

Back 2

Kernel/User.

Front 3

What mode does the OS run in?

Back 3

Kernel.

Front 4

How can a program enter kernel mode?

Back 4

Software trap (interrupt intended to initiate a context switch).

Front 5

What functions are usually forbidden in user mode?

Back 5

I/O and memory functions.

Front 6

What do I/O devices consist of?

Back 6

The device itself, and a controller (with registers).

Front 7

What talks to an I/O device controller?

Back 7

Device driver.

Front 8

Why bother having an OS?

Back 8

Each application would be responsible for running the computer!

How would all devices communicate?

Programmers shouldn't have to worry about low level stuff.

Front 9

Where does the OS exist?

Back 9

On top of the hardware, below application programs.

Front 10

What mode does the Kernel run in? Why?

Back 10

kernel mode (supervisor mode) to protect it from tampering.

Front 11

What 4 things does an OS do?

Back 11

Hides details of work.

Multi-task.

Allow programs to share resources in time.

Allow programs to share resources in space.

Front 12

What are two perspectives of an OS?

Back 12

Extended Machine - Hardware communication.

Resource Manager - Each program given time/space. OS is the scheduler.

Front 13

What are the 7 types of OS?

Back 13

Mainframe.
Server.
Multiprocessor.

PC OSs.
Real-Time Operating Systems.

Embedded OSs

Smart Card Operating Systems.

MSM-PRES
Ma server multitasks presents

Front 14

What is a process?

Back 14

A program in execution to which we have given resources.

Front 15

What resources are associated with a process?

Back 15

The process' address space.
Set of registers.
Priority.
Opened files.
Signals awaiting by the process.

Front 16

Where is information about processes stored?

Back 16

Into a structure called a process table.

An entry in the process table will exist for each process and they are grouped together as an array or a linked list.

Front 17

What are the signals received by processes from the OS called?

Back 17

Alarm Signals (Software equivalent to interrupts).

Caused by timers controlled by the OS or by Hardware.

Front 18

An OS assigns what number to the process based on the user that started it? What does this affect?

Back 18

UID (User Identification).

What features of the operating sytstem they can access.

Front 19

What are the short comings of evenly allocating available memory per n proccesses?

Back 19

Wastes memory.
Limits all processes to an artificially small size.
Limits the number of processes that may execute.

Front 20

What is a solution to dividing memory per n processes?

Back 20

Virtual memory:

Part of the address space is maintained on the disk. Parts of processes are moved between disk and main memory when required.

Front 21

When are system calls required for handling files?

Back 21

File opening, closing, creation, deletion, reading, and writing.

Directory creation and deletion. Addition/removal of files to and from hierarchies.

Front 22

Files in UNIX are protected by a 9-bit code.

Front 23

Is the shell part of the operating system?

Back 23

No, but it is closely linked.

Front 24

What are system calls?

Back 24

The interface between user programs and the operating system.

Front 25

How do you create a new process in *NIX OS?

Back 25

fork()

Front 26

s = execve(name, argv, environp)

Replaces the proccess' core image with name program
argv is a pointer to an array of characters
environp is an array of environment information.