OS REVIEWER
PRELIM
Window Graphing System – It implements a graphical user
interface, such as user interface controls and illustrations.
File Tables – These are used to hold information about the
existence files
I/O status information – different information associated with
the input/output statue
Interrupts – external event are independent
Application Binary Interface – standard binary portability
Program counter – address of the next instruction to be
executed
Job – single program numerous sequenced set up process
Linux Operating System – free open-source variant of the UNIX
operating system
Process Control Information – additional information the OS
need to control
User Mode – less-privileged execution mode
Security Reference Monitor – enforces the access validation
and audit-generation
I/O tables – manage computer systems input/output devices
Exit State – released from the pool of executable process
Multi-programmed Batch System – compared to single –
programmed system
Application Binary Interface - Collection of machine language
instructions that computer to follow.
TRUE about process attributes
-They consist of processor registrar information
TRUE about time-sharing systems
-They allow multiple users simultaneously access system
through terminate
TRUE about android system
-It is a Linux based system originally designed for mobile phones
NOT TRUE about serial processing
-It allows the processor to handle multiple jobs at a time
TRUE about a trap in process switching
-It relates to errors generated within the currently running
process
NOT attributed to a process during program execution
-The same identifier to each process
NOT described a process
-It is a storage data structure
TRUE about kernel mode as an execution mode
-It lets software control the processor and its instructions and
registers.
TRUE about windows operating systems
-It operates the core OS software from the application-oriented
software
NOT an operating system service as a compiler interface
-Management of virtual addresses, physical memory, and paging
files on a disk.
TRUE about halt instruction In process termination
-It generates an interrupt alert the OS that a process has been
completed
TRUE about simple batch system
-They process jobs in bulk
TRUE about process identification
-It involves unique numeric identifiers
NOT an OS function
-Extension of system functionality and running background user-
mode activity
MIDTERM
Solaris – Operating Systems implements the combined
approach.
Race Condition – It is a situation where multiple threads read
and write a shared data item.
Unblocked – This Operation moves blocked thread into the
ready queue for the continuation of its execution.
Hold and wait – The condition is prevented by requiring a
process to request all its required sources simultaneously.
Responsive – Multithreading allows a program to continue
running even if some part of it is blocked or performing a lengthy
operation. This benefit is known as
Resource allocation graph – It is a useful tool in characterizing
the allocation of resources to processes.
Condition Variable – It is used to block a process or a thread
until a specific condition is true.
Multithreading – This is the ability of an OS to support
concurrent paths of execution within a single process.
Binary – this semaphore only takes the value of zero and one.
Base Priority – It is the lower limit of the threads dynamic
priority.
Distributed Processing – It is the management of multiple
processes executing on multiple distributed computer systems.
Multicore System – These affect the application design and
performance when applications with multiple threads are
provided.
Alert Status – It indicates whether a waiting thread may execute
an asynchronous procedure call.
Combined Approach – This approach runs multiple threads
within the same application in parallel on multiple processors.
Monitor – This programming construct encapsulates variables
and initialization code within an abstract state type.
All Process Threads share the same address space and
resources – processes may exist where both resources and
threads arrangement.
Processes may exit while holding resources – not a restriction
in implementing the deadlock avoidance strategy.
The ability to communicate with each other by process
identification – not an operating system concern caused by
existence of concurrency.
It involves conflicting needs for resources by two or more
processes – not true about concurrency.
The separated one OS software from the application-
oriented software – not true about multithreading.
Aborting External deadlock process – not a recovery method
in deadlock detection.
It only takes the values of zero and one – not true about
counting semaphore.
Schedule thread whenever a process is blocked – not a
benefit of multithreaded programming.
A resource is not preempted – condition must be present for a
deadlock to occur.
They encompass the ability to load and execute multiple
runnable program – not true about deadlock.
It executes an infinite loop – not true about the monitor
mechanism.
Kernel maintains the context information for the process –
not true about combined approach.
Thread management code is not needed on the application
level – not an advantage of user-level threads.
An application that only processes binary data – not
multithreaded application.
A web browser that display images or text – not attributed to
threads.
PREFINALS
Waiting Time - The Criterion is the sum of the personnel spent
waiting in the ready queue
Simple paging - This technique divides the memory into several
equality sizes frames
Job queue - The queue contains all the processes in the system
Shortest remaining time first - This is an algorithm in which the
process with the smallest execution time is chosen for the next
execution.
Execution Time - This criterion deals with the time required for
process to be executed by the control processing unit.
Medium term Scheduler - The scheduler handles swapped-out
processes in scheduling
Virtual Memory Paging - This partitioning method processes
the same as simple segmentation but has no internal
fragmentation
Round Robin - This algorithm involves the generation of a clock
interrupt at periodic intervals
Physical Addresses - This loader generates these addresses
when a program is loaded into the main memory
Swapping - It is also known as memory compaction
Virtual Memory Paging - The partitioning method processes the
same as simple paging but has no external fragmentation
Throughput - The criterion measures how much work is
performed by the processor
Best – Fit - This placement algorithm chooses the block closest
to the requested size in partitioning
Simple Segmentation - This Technique divides each process
into several segments
Virtual Memory - It provides processes and a kernel with a
private view of its main memory
True/False
True about long term Scheduling – it is also known as job
scheduler
Not a requirement that memory management intends to
satisfy? – The Act of a selecting as task or a job to be
dispatched.
Which of the following best describes the shortest remaining
time first algorithm?
- It is the estimated processing time to perform the selection
function.
Which of the following statements is NOT considered a
virtual memory characteristic?
- It provides fast access at a relatively high cost
Which of the following statements is TRUE about turnaround
time?
- It is the difference between the finish time and the arrival time
What does fairness in scheduling mean?
- Process should be treated the same
Which of the following is NOT considered a scheduling
criterion?
- The average rate of placement algorithm
Which of the following statements TRUE about response
time?
- It is time to submit a request until the response is received
Which of the following statements is NOT TRUE about
memory management?
-It Hold data that is in use
Which of the following statements is NOT TRUE about virtual
memory segmentation?
-It is similar to simple paging
Which of the following statements is TRUE about dynamic
partitioning?
-It has no Internal fragmentation
Which of the following statements is TRUE about fixed
partitioning?
-It only produces a minimal operating system overhead.
Which of the following statements is TRUE about simple
paging?
-It may cause a small amount of internal fragmentation.
Which of the following best describes the shortest job first
algorithm?
-It is best approach to minimize the waiting time.
Which of the following statements is NOT TRUE about
process scheduling?
-It divides CPU time among active processes and thread
FINALS
Input/output (I/O) devices - hardware devices that can accept
input, deliver output, and/or managing other processed data.
Human-readable devices – communicating with computer
users. Examples: Keyboard and mouse
Machine-readable devices – communicating with electronic
equipment. Examples: Sensors and controllers
Communication devices – communicating with remote
devices.
Examples: Digital line drivers and modems
Data transfer rate – amount of digital data that is moved from
one location to another within a specific time.
Application – specific use of the device that commonly
depends on its actual purpose.
Control complexity – level of difficulty in operating the device.
Unit of transfer – whether data is transferred as a stream
Data representation – data encoding scheme that is used by
the device that includes character codes and parity
conventions.
Error conditions – nature of errors
Device controllers – electrical and mechanical component,
technically work like an interface between an actual device and
a device driver.
Device driver - is a software module that can be plugged into
the operating system
Port - A connection point
Bus - share a common set of wires
Block-oriented device – stores information in blocks that are
usually fixed in size
Stream-oriented device – transfers data in and out as a stream
of bytes, without any block structure.
Programmed I/O - programmed to cross-examine I/O devices to
check the readiness of the device for data transfer
Interrupt-driven I/O - The processor issues an I/O command on
behalf of a process that may lead to either of the following:
• If the I/O instruction from the process is nonblocking,
then the processor continues to execute instructions
from the process that issued the I/O command.
• If the I/O instruction is blocking, then the next instruction
that the processor executes is from the OS, which will put
the current process in a blocked state and schedule
another process.
Direct memory access (DMA) - controls the exchange of data
between the main memory and the device driver.
Logical I/O – This layer deals with the device as a logical
resource and concerned with managing general I/O functions
Device I/O – In this layer, the requested operations and data are
converted into an appropriate sequence of I/O instruction
Scheduling and control – This layer involve the queueing and
scheduling of the I/O operations
Buffering - is a technique that smoothens out peaks in I/O
demands. (Is like waiting room for data)
Single Buffer - the simplest type of support an operating system
can provide. user processes an I/O request, the OS assigns a
buffer in the system portion of the main memory to the
operation.
Double Buffer - This involves the assignment of two (2) system
buffers to an operation.
Double buffering or buffer swapping - A process transfers data
to (or from) one (1) buffer while the OS empties (or fills) the other
buffer.
Circular Buffer - Utilizing double buffer may be inadequate if
the process performs rapid busts of I/O. In this case, using more
than two (2) buffers can alleviate inadequacy. A collection of
buffers are called a circular buffer, where each individual buffer
is treated as one (1) unit.
Seek time – This is the time required to move the disk arm to the
required track. It is composed of two (2) components: the
startup time and the time
Rotational delay – This is the time required for the addressed
area of the disk to rotate into a position where it is accessible by
the read/write head. This is also known as rotational latency.
Transfer time – This depends on the rotation speed of the disk,
which is equal to the number of bytes to be transferred (b)
divided by the product of the rotation speed (r) and the number
of bytes on a track (N). Formula: T = b/(rN)
First-in First-out (FIFO) – This is the simplest form of scheduling
policy that processes items from the queue in sequential order.
Last-in First-out (LIFO) – In transaction-processing systems,
giving the device to the most recent user should result in little or
no arm movement for moving through a sequential file.
Priority - Requests are processed based on assigned priority,
not order of arrival. For example, short tasks may be prioritized
over long ones.
Shortest Service Time First (SSTF) – This scheduling policy
selects the disk I/O request that requires the least movement of
the disk arm from its current position.
SCAN – This is also known as the elevator algorithm because it
operates much like an elevator.
Circular SCAN (C-SCAN) – This policy restricts scanning to one
(1) direction only.
N-step SCAN – This scheduling policy segments the disk
request queue into sub-queues of length N. Sub-queues are
processed one (1) at a time, using SCAN.
FSCAN – This policy utilizes two (2) sub-queues. Initially, when
the scan begins, all requests are placed in one of the sub-
queues, while the other sub-queue is empty.
Redundant array of independent disks (RAID) - is a
standardized scheme for multiple-disk database design that is
composed of seven (7) levels, from zero (0) to six (6).
Caches - are used by operating systems to improve file system
read performance, while their storage is often used as buffers to
improve writing performance.
term cache memory - is used to indicate a memory that is
smaller and faster to access than the main memory.
File system - is an organization of data as files and directories
Long-term existence: Files are stored on disk or on other
secondary storage that must not disappear when a user logs off.
Sharable between processes: Files have names and
associated access permission that permit controlled sharing.
Good structure: A file can have an internal structure that is
suitable for applications.
Field – This is the basic element of data.
Record – This is a collection of related fields that can be treated
as a unit by an application or a program.
File – This is a collection of similar records.
Database – This is a collection of related data.
Create: A new file is defined and positioned within the file
structure.
Delete: A file is removed from the file structure and
subsequently be obliterated.
Open: An existing file is opened by a process allowing the
process to perform other operations on the file.
Close: An existing file is closed with respect to a process so that
the process may no longer perform any operation on the file.
Read: A process reads all or a portion of the data in the file.
Write: A process updates a file either by adding new data that
may increase the file size or by changing values of existing data
items in the files.
File name – It is a symbolic name for a file that is kept in human-
readable form.
Identifier – It is a unique tag that identifies a file within the file
system.
• File type – This information is needed for systems that support
different types of files.
• Location – This serves as a pointer to a device and to the exact
location of the file on a particular device.
• File size – It is the current size of a file in bytes, words, or in
blocks.
• Protection – It pertains to the access control information of the
file that determines who can read, write, or execute other
operations on the file.
• Timestamp – This information usually involves the time of
creation, last modification, and last access time that are used
for security and monitoring.
File organization - pertains to the logical structure of records as
determined by the way in which they are accessed.
Pile – This is the least complicated form of file organization.
Sequential file – This is the most common form of file
organization, since it implements a fixed format for records.
Indexed sequential file – This is a well-known approach to
overcome the disadvantages of a sequential file structure.
Indexed file – This file organization encompasses multiple
indexes, one for each type of field that may be the subject of a
search.
• exhaustive index - that holds one (1) entry for every
record in the main file
• partial index - that holds entries to records where the
field of interest exists.
Direct/Hashed File – This file organization exploits the
capability found on disks to directly access any block of data
with known address.