Tuesday, 28 February 2012

UGC NET Paper I

1. Research is:
(a) A fault activity
(b) An activity that helps in development
(c) An interesting activity
(d) An activity that adds to happiness of the people
2. A researcher should always:
(a) Know everything in his area
(b) Know about sub-area
(c) Wait for an inspiration
(d) None of the above
3. Which of the following best sums up the objective of hypothesis?
(a) It places clear goals for the researcher
(b) It prevents the researcher from undertaking blind research
(c) It enables the researcher to draw conclusions.
(d) It lays down the rules for undertaking the research
4. One undertakes research for which of the following purpose?
{a) To verify what has been established
(b) To refute some assumptions
(c) To describe a new phenomenon
(d) Either of a, b or c
5. Research promises advancement of knowledge but discoveries are rare bee
(a) Research is a critical, continuous investigation
(b) Researchers are not creative enough to solve problems
(c) Sustained effort at research is lacking these days
(d) Most people lack the aptitude for research
6. Language is a
(a) Instinctive development
(b) System of symbols for effective communication
(c) Medium to express experiences
(d) Medium for self enhancement
7. An individual's ability to learn is
(a) Absorbed
(b) Acquired
(c) Occurring from within
(d) Developed
8. Bibliography given in a research report
(a) Helps those interested in further research and studying the problem from a angle.
(b) Shows the vast knowledge of the researcher
(c) Makes the report authentic
(d) None of the above
9. The research antagonistic to ex-post facto research is
(a) Experimental studies
»
(b) Library researches
(c) Normative researches
(d) all of the above
10. An example of scientific knowledge is
(a) Social traditions and customs
(b) Authority of the prophet or great men
(c) Religious scriptures
(d) Laboratory and field experiments
11. The process not needed in experimental researches is
(a) Controlling
(b) Observation
(c) Manipulation and replication
(d) Reference collection
12. Research promises advancement of knowledge but discoveries are rare because:
(a) Research is a critical, continuous investigation
(b) Researchers are not creative enough to solve problems
(c) Sustained effort at research is lacking these days
(d) Most people lack the aptitude for research
13. In any discipline, theories and observations (related experiment results):
(a) Should complement each other
(b) more often than not should contradict each other
(c) Need not have anything to do with each other
(d) should compensate each other
14. If I do not get a satisfactory explanation to certain occurrences.
(a) It may not be worth knowing at all
(b) It would be better to wait for a person who can explain it
(c) It would be better to visit a nearby research institute to get more information
(d) I would not be at rest till I get a correct explanation
15. All are example of qualitative variables except
(a) Sex
(b) Religion and castes
(c) Observation
(d) Interest of the subject
16. If the sample drawn does not specify any condition about the parameter of the population, it is called
(a) Selected statistics
(b) Distribution free statistics
(c) Census
(d) Non of the above
17. Attributes of objects, events of things which can be measured are called
(a) Data
(b) Qualitative measure
(c) Variables
(d) None of the above
18. In order to augment the accuracy of the study a researcher
(a) Should be honest and unbiased
(b) Should increase the size of the sample
(c) Should kept the variance high
(d) all of these
19. Hypothesis cannot be stated in
(a) Declarative terms
(b) Null and question form terms
(c) General terms
(d) Directional terms
20. All causes non sampling errors except
(a) Faulty tools of measurement
(b) Inadequate sample
(c) Defect in data collection
(d) Non-response
21. Formulation of hypothesis may not be necessary in
(a) Survey studies
(b) Fact finding (historical) studio
(c) Experimental studies
(d) Normative studies
22. Who is regarded the father of scientific social surveys?
(a) Best
(b) Booth
(c) Darwin
(d) None of these
23. A good piece of research is a product of:
(a) Collective scholarship
(b) a good library
(c) A penetrating and analytical mind
(d) a touch of genius
24. What is statistical inference?
(a) Reaching conclusions from a sample
(b) Analyzing statistical data
(c) Applying statistical methods
(d) Developing statistical theories
25. Which of the following is not correct? A belief becomes a scientific truth when
(a) Is established experimentally
(b) Is arrived logically
(c) Is accepted by many people
(d) can be replicated
26. The experimental study is based on the law of
(a) Single variable
(b) Occupation
(c) Replication
(d) interest of the subject
27. Fordoing external criticism (for establishing the authenticity of tin a) a rese must verify
(a) Signature and handwriting of the author
(b) The paper and ink used in that period which is under study
(c) Style of prose writing of that period
(d) all of the above
28. Survey study aims at
(i) Knowing facts about the existing situation
(ii) Comparing the present status with the standard norms
(iii) Criticizing the existing situation
(iv) Identifying the means of improving the existing situation
(a) (i) And (ii) only
(b) (i), (ii). And (iv)
(c) (i), (ii), (iii) And (iv)
(d) (ii) And (iii) only
29. Which of the following is not the characteristic of a researcher?
(a) He is industrious and persistent on the trial of discovery
(b) He is a specialist rather than a generalist
(c) He is not inspirational to his chosen field but accepts the reality
(d) He is not versatile in his interest and even in his native abilities
(e) He is versatile in his interest even in his native abilities
(f) He is objective
30. The validity and reliability of a research will be at stake when -
(a) The incident was reported after a long period of time from that of its occurrence
(b) The author who is the source of information is biased, incompetent of dishonest
(c) The researcher himself is not competent enough to draw logical conclusions
(d) All of the above
31.
A researcher wants to study the future of the Congress I in India. For the study which tool is most
appropriate for him?
(a)
Picnics/excursions
(b)
mock-parliament
(c)
Celebration of festivals
(d)
all of the above
32. seeing a very big it was reported that JD will win the election, the conclusion was based on
(a) Random sampling
(b) Cluster sampling
(c) Purposive sampling
(d) Systematic sampling
33. A researcher divides his population into certain groups and fixes the size of the sample from each
group. It is called
(a) Stratified sample
(b) Quota sample
(c) Cluster sample
(d) all of the above
34. Which technique is generally followed when the population is finite?
(a) Purposive sampling technique
(b) Area sampling technique
(c) Systematic sampling technique
(d) None of the above
35. Which of the following is a non-probability sample?
(a) Quota sample
(b) Simple random sample
(c) Purposive sample
(d) (a) and (c) both
36. A researcher selects a probability sample of 100 out of the total population. It is
(a) Cluster sample
(b) A random sample
(c) A systematic sample
(d) A stratified sample
37. A good hypothesis should be
(a) Formulated in such a way that it can be tested by the data
(b) Precise, specific and consistent with most known facts
(c) Of limited scope and should not have global significance {d) all o these
38. While writing research report a researcher
(a) Must arrange it in logical, topical and chronological order
(b) Must not use the numerical figures in numbers in the beginning of sentences
(c) Must compare his results with those of the other studies
(d) all of the above
39. Which of the following is a primary source of data?
(a) Official records - governments documents, information preserved by social religious organization etc.
(b) Personal records, letters, diaries, autobiographies, wills, etc.
(c) Oral survey of traditions and customs
(d) All of the above
40.
A farmer considers the age-old method of ploughing better then the latest methods available to him.
In arriving at this conclusion, he is being influenced by: «
(a)
Tradition
(b)
Experience
(c)
Reason
(d)
Experimentation
41.
Consider the following statement: 'Observations, in themselves, are of little statement.' What is the
basis of making such a statement?
(a)
They are without any purpose
(b)
They must be related to other facts for generalization
(c)
They are not systematic and not amenable to scientific interpretation
(d)
They are meaningful only if collected by a scientist
42.
(a)
(b)
(c)
Logic of induction is very close to
The logic of sampling
The logic of the controlled variable
The logic of observation
(d) none of the above
43. Field study is related to
(a) Real life situations
(b) Laboratory situations
(c) Experimental situations
(d) None of the above
44.
A researcher divides the populations into PG, graduates and 10+2 students and using the random digit
table he selects some of them from each. This is technically called.
(a)
Settled sampling
(b)
Stratified random sampling
(c)
Representative sampling
(d)
None of these
45. Generalized conclusion on the basis of a sample is technically known as
(a) Statistical inference of external validity of the research
(b) Parameter inference
(c) Data analysis and interpretation
(d) all of the above
46. Validity of a research can be improved by
(a) Taking the true representative sample of the population
(b) Eliminating extraneous factors
(c) %
(d) Both the above measures
   None of these
47. In higher education, research and education are two activities that:
(a) Cannot go together
(b) Can go only in sequential order
(c) Can go together
(d) Can go together but at the expense of each other
48. for a proposition to be true, it is necessary that it should have all of the following excepts:
(a) It must be objective
(b) It must be in tune with accepted beliefs
(c) It must be consistent
(d) It must be testable
49. Which of the following is not the requirement of a hypothesis? It should:
(a) Be based on facts
(b) Be conceivable
(c) Contradict the knowledge of nature
(d) Allow consequences to be deducted from it
50. Which of the following is most reasonable about teaching and research activities?
(a) Both are entirely different activities
(b) Both cannot be done side by side
(c) Both are two aspects of the same coin
(d) Both could hinder one another
51. My reaction to the statement: "A good teacher is essentially a good researcher" is that this is:
(a) My firm belief
(b)
(c)
(d)
Difficult to agree to
It is an opinion
Only a hypothesis
52.
The first question that a researcher interested in applying statistical techniques to his problem has to
ask is:
(a)
Whether data could be qualified or quantified
(b)
Whether appropriate statistical techniques are available
(c)
Whether analysis of data would be possible
(d)
Whether worthwhile inferences could be drawn
53.
The main difference between an administrator and researcher lies in the fact that:
(a)
The former is more concerned only with the what of things while the researcher is interested in both
the what and why of things.
(b)
The former approaches problems in a practical manner while the later is purely theoretical
(c)
The former takes a global view while the later penetrates deep into specific issues
(d)
The former is more interested in social outcomes while the later in finding out as to why things happen
as they do.
54. Which would be acceptable for establishing a fact?
(a) Opinion of a large number of people
(b) Traditional practice over a lone period of time
(c) Availability of observable evidence
(d) reference in ancient literature
55. Research aim at:
(a) Control of concerned matter
(b) Understanding of concerned matter
(c) Human welfare with help of concerned matter
(d) Prediction of concerned matter
56.`The research supervisors require the following as essential qualities:
(a) `Expertise of subject matter
(b) `Methodological
(c) `Interdisciplinary
(d) `Which is true
(i) ``Only A
(ii) `Only B
(III) Both A & B
(iv) `All
57.
(a)
(b)
(c)
(d)
A good research always begins with:
An original idea
Preparation of plan and design for study
Study of relevant research methodology
Review of literature
58.
In every field research promotes systematic and gradual advancement of knowledg but still discoveries
are rare:
(a)
It requires a continuous critical investigation
(b)
Experimental work needed for discovery is not easily forthcoming
(c)
Most people lack depth of knowledge for it
(d)
Not able to think beyond a point
59. Sin - qua- non of good research is:
(a) Well formulated hypothesis
(b) Good research supervisor
60. Which of the following is not a quality of scientific research?
(a) Imagination
(b) Creativity
(C) Objectivity
(d) Subjectivity
61. Objectivity in research implies:
(a) Correct judgment of truth
(b) Finding consistency with reality
(c) Research - researcher agreement
(d) Methodological sophistication
62. One undertakes research:
(a) To verify what has already been established
(b) To refute what has already been accepted as a fact
(c) To describe and explain a new phenomenon
(d) one or more of above
63. The valid base of knowledge lies in:
(a) Customs and traditions
(b) Authority
(c) Scientific enquiry
(d) Personal experience
64. Research process and scientific thinking are
(a) Unrelated process
(b) Process of enquiring new knowledge with different emphasis
(c) Synonymous
(d) Similar in some situations and dissimilar in others
65. Building up of theory is the aim of:
(a) Action research
(b) Fundamental research
(c) Historical research
(d) Applied research
66. Action research has its origin in:
(a) Modern human organization & theory
(b) System approach to education
(c) Logical thinking process
(d) Educational technology
67. Random sampling doesn't:
(a) Make the sample: representative of population
(b) Ensure generalization of result
(c) Reduce error and increase precision of experiment
(d) Maximum experimental variance
68. Which one of the variable is not discrete variable?
(a) Age
(b) Company bonds
(c) Place of residence
(d) Sex
69. For a proposition to be true, it is necessary that it should have all of the followings:
(a) It must be objective
(b) It must be consistent
(c) It must be testable
(d) It must be in tune with accepted beliefs
70. What is not correct?
(a) A beliel becomes a scientific truth when it is established experimentally
(b) It is arrived at logically
(c) It is accepted by many people
(d) It can be replicated
71. from the following qualities which are essential for research scientists:
(a) Keenness
(b) Persistence
(c) Faith
(d) Logical reasoning
72. What is statistical inference?
(a) Reaching conclusion from a sample
(b) Analyzing statistical data
(c) Applying statistical methods
(d) Developing statistical theories
73. Sample is to population as:
(a) Large: Small
(b) False: True
(c) Part: Whole
(d) Commerce: Science
74. The process from where one proceeds from some given truth to an unknown truth is:
(a) Stating a conclusion
(b) Stating a premise
(c) Making a judment
(d) Making a inference
75. Qualitative research differs from quantitative research as it:
(a) Views phenomenon in a holistic manner
(b) Uses survey instead of experimentation
(c) It is cross sectional in nature
(d) It is highly objective
76. Two variables are correlated:
(a) If with the change in one variable other variable also changes
(b) Change of variables are in opposite direction.
(c) "Two variables are similar in nature
(d) Two variables are dissimilar
77. The sampling design the purpose of which is to reduce per unit cost:
(a) Simple random
(b) Cluster
(c) Systematic
(d) Stratified

ANSWERS


(1) b (2) b (3) a (4) d (5) a (6) c (7) c (8) a (9) a (10) d (11) d (12) a (13) a (14) d (15) d (16) b (17) c (18) d (19) c (20) b (21) b (22) b (23) c (24) a (25) a (26) a (27) d (28) b (29) d (30) d (31) a (32) b (33) b (34) c (35) d (36) b (37) d (38) d (39) c (40) a (41) b (42) a (43) a (44) b (45) a (46) c (47) c (48) b (49) a (50) c (51) a (52) a (53) d (54) c (55) c (56) iv (57) d (58) a (59) d (60) b (61) b (62) d (63) c (64) d (65) b (66) a (67) d (68) a (69) d (70) c (71) d (72) a (73) c (74) d (75) b (76) a (77) b

Saturday, 18 February 2012

Notes on OperatingSystem

Chapter 1 – Introduction to OS

What is an Operating System?

§       Operating System is a Resource Manager.
      Handles multiple computer resources: CPU, Internal/External memory, Processes, Tasks, Applications, Users, etc…
      Manages and allocates resources to multiple users or multiple jobs running at the same time (e.g., processor time, memory space, I/O devices)
      Arranges to use the computer hardware in an efficient manner (maximize throughput, minimize response time) and in a fair manner.

§       It is a Control Program.
      Manages all the components of a complex computer system in an integrated manner. 
      Controls the execution of user programs and I/O devices to prevent errors and improper use of the computer resources.
      Looks over and protects the computer.

§       It is an extended/virtual machine
-      An interface between the user and hardware that hides the details of the hardware (e.g., I/O).
-      Constructs higher-level (virtual) resources out of lower-level (physical) resources (e.g., files).
-      Definition: Is a collection of software enhancements, executed on the bare hardware, culminating in a high-level virtual machine that serves as an advanced programming environment


Why Operating System?

§       Computer hardware is developed to execute user programs and make solving user problems easier.

§       An operating system makes a computer more convenient to use.
-      It acts as an interface between user and computer hardware. Therefore, the end-users are not particularly concerned with the computer’s architecture, and they view the computer system in terms of an application.
-      To programmers, it provides some basic utilities to assist him in creating programs, the management of files, and the control of I/O devices.



Operating System Objectives

§       Convenience
-      Makes the computer more convenient to use
§       Efficiency
-      Allows computer system resources to be used in an efficient manner
§       Ability to evolve
-      Permit effective development, testing, and introduction of new system functions without interfering with service

Services Provided by Operating Systems

§       Facilities for program creation
-      Editors, compilers, linkers, debuggers, etc.

§       Program execution
-      Loading in memory, I/O and file initialization.

§       Access to I/O and files
-      Deals with the specifics of I/O and file formats.

§       System access
-      Resolves conflicts for resource contention.
-      Protection in access to resources and data.

§       Error detection and response
-      internal and external hardware errors
§       memory error
§       device failure
-      software errors
§       arithmetic overflow
§       access forbidden memory locations
-      operating system cannot grant request of application

§       Accounting
-      collect statistics
-      monitor performance
-      used to anticipate future enhancements
-      used for billing users

Computer System Components

§       A computer system can be divided in to four components.

-      The Hardware: Provides basic computing resources (CPU, memory, I/O devices).

-      The Operating System: Controls and coordinates the use of the hardware among the various application programs for the various users.

-      The Application Programs: Define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs).

-      The Users: Users (people, machines, other computers).



§       These components can be viewed as layers, where each layer uses the services provided by the layer beneath it.

 













A Static View of System Components



Dynamic View of System Components
Another view of computer system components

History of Operating Systems

§       Let’s see how operating systems evolve over time.
§       This will help us to identify some common features of operating systems and how and why these systems have been developed as they are.

Evolution of Operating Systems

§       Early Systems (1950)
§       Simple Batch Systems (1960)
§       Multiprogrammed Batch Systems (1970)
§       Time-Sharing and Real-Time Systems (1970)
§       Personal/Desktop Systems (1980)
§       Multiprocessor Systems (1980)
§       Networked/Distributed Systems (1980)
§       Handheld Systems (1990)

Early Systems

§       Structure
-      Single user system.
-      Large machines run from console.
-      Programmer/User as operator.
-      Paper Tape or Punched cards.
-      No tapes/disks in computer.

§       Early software: Assemblers, Libraries of common subroutines, Device Drivers, Compilers, Linkers.
§       Significant amount of setup time.
§       Low CPU utilization.
§       But very secure.

Simple Batch Systems


§       Mainframe machines. Input devices were card readers. Output devices were line printer, tape drives, and card punch.
§       A job (a single program+ associated data + control information) usually on the punch cards submitted to the operator.
§       The output consisted of the results of the program or memory dump in case of error.
§       The operator used to batch together similar programs and run as a group to reduce setup time.
§       No user interaction while the job is executing.
§       Current examples include .bat files under Dos – Windows and shell files under Unix/Linux.
Example of card deck of a job

§       The operating systems (called resident monitor) manages the execution of each program in the batch.
-      Monitor utilities are loaded when needed.
-      Resident monitor is always in main memory and available for execution.
-      The resident monitor usually has the following part.
§       Control card interpreter – responsible for reading and carrying out instructions on the cards.
§       Loader – loads systems programs and applications programs into memory.
§       Device drivers – know special characteristics and properties for each of the system’s I/O devices.


§       In batch systems:
-      Initial control is in monitor.
-      Load next program and transfer control to it.
-      When a job completes, the control transfers back to monitor.
-      Automatically transfer control from one job to another (Automatic job sequencing).

Problems

§       Slow Performance – I/O and CPU could not overlap; card reader very slow.
§       CPU was often idle.

Solutions

1.    Off-line Operation
-      Speed up computation by loading jobs into memory from tapes while card reading and line printing is done off-line using smaller machines.


2.    Use spooling (Simultaneous Peripheral Operation On Line).
-      Cards are read directly from the card reader onto a disk and location of card images are kept in a table by the operating system.
-      The output is sent to the disk and when the job is completed then the output was actually printed.
-      I/O and computations were overlapped. While executing one job, the OS:

-      Reads next job from card reader into a storage area on the disk (job queue).
Outputs printout of previous job from disk to printer.
§        


Uniprogramming Until Now

§       I/O operations are exceedingly slow (compared to instruction execution).
§       A program containing even a very small number of I/O operations will spend most of its time waiting for them.
§       Hence: poor CPU usage when only one program is present in memory.



Memory Layout of Uniprogramming















Memory layout of a simple batch processing system

 

Multiprogrammed Batch Systems


§       Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.















§       If memory can hold several programs, then CPU can switch to another one whenever a program is waiting for an I/O to complete – This is multiprogramming.

 


OS Features Needed for Multiprogramming


§       I/O routine supplied by the system.
§       Memory management – the system must allocate the memory to several jobs.
§       CPU scheduling – the system must choose among several jobs ready to run.
§       Allocation of devices.

Time Sharing Systems (Interactive Systems)

§       TSS extends Batch multiprogramming to handle multiple interactive jobs – It’s Interactive Multiprogramming.
§       Multiple users simultaneously access the system through terminals.
§       Processor’s time is shared among multiple users, that is, the CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory).
§       On-line communication between the user and the system is provided; when the operating system finishes the execution of one command, it seeks the next “control statement” from the user’s keyboard.
§       TS system provides each user with her/her own virtual machine.

 

Multitasking

§       TS eventually supports multitasking.
§       A time share system that supports multiple processes (program in execution) per user is called a multitasking system.

Why Does Time Sharing Work?

§       Because of slow human reaction time, a typical user needs 2 seconds of processing time per minute.
§       Then many users should be able to share the same system without noticeable delay in the computer reaction time.

Batch Multiprogramming




Vs. Time Sharing


Batch Multi-Prog.
Time Sharing
Principle obj.
Max. Processor use
Min. response time
Source of inst. To OS
JCL provided with the job
Commands entered at the terminal

OS Features Needed for Time Sharing Systems

§       On-line file system must be available for users to access data and code.
§       Should do memory management
§       Should do CPU scheduling
§       Should do job synchronization and have communication facilities.
§       Should ensure that dead lock and indefinite waiting does not occur.
§       Should allow sharing of computer resources.

Personal Computer Systems

§       Personal computers – computer system dedicated to a single user.
§       Have a wide variety of I/O devices – keyboards, mice, display screens, small printers.
§       User convenience and responsiveness are of prime importance.
§       Can adopt technology developed for larger operating system.
§       Often individuals have sole use of computer and do not need advanced CPU utilization of protection features.
§       May run several different types of operating systems (Windows, MacOS, UNIX, Linux)
Two Categories of Computer Systems

§       Single Instruction Single Data (SISD)
-      Single processor executes a single instruction sequence to operate on data stored in a single memory.
-      This is a Uniprocessor.

§       Multiple Instruction Multiple Data (MIMD)
-      A set of processors simultaneously execute different instruction sequences on different data sets.
-      This is a Multiprocessor.

Multiprocessor Systems


§       Multiprocessor systems have more than one CPU in close communication.
-      Tightly coupled system – processors share memory and a clock; communication usually takes place through the shared memory.
§       Advantages of parallel system:
-      Increased throughput
-      Economical
-      Increased reliability
§       Graceful degradation


Multiprocessor architecture

Symmetric Multiprocessing (SMP)


§       Each processor runs an identical copy of the operating system.
§       Each processor can perform the same functions and share same main memory and I/O facilities (symmetric).
§       The OS schedules processes/threads across all the processors (real parallelism).
§       Existence of multiple processors is transparent to the user.
§       Incremental growth: just add another CPU!
§       Robustness: a single CPU failure does not halt the system, only the performance is reduced.
§       Many processes can run at once without performance deterioration.
§       Most modern operating systems support SMP

Asymmetric multiprocessing

§       Each processor is assigned a specific task; master processor schedules and allocated work to slave processors.
§       More common in extremely large systems


Distributed Systems



§       Distribute the computation among several physically separated processors.
-      Loosely coupled system – each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.
§       Advantages of distributed systems.
-      Resources Sharing
-      Computation speed up – load sharing
-      Reliability and fault tolerance
-      Communications
§       Requires networking infrastructure - Local area networks (LAN) or Wide area networks (WAN)
§       May be either client-server or peer-to-peer systems.





 
















General structure of client-server


Peer-to-peer systems

Network Operating System

§       Provides file sharing
§       Provides communication scheme
§       Runs independently from other computers on the network

Distributed Operating System

§       Less autonomy between computers
§       Gives the impression there is a single operating system controlling the network.

Clustered Systems

§       Clustering allows two or more systems to share external storage and balance CPU load.
§       Asymmetric clustering: one server runs the application while other servers standby.
§       Symmetric clustering: all N hosts are running the application.






Real-Time Systems


§       Note that not all Operating Systems are general-purpose systems.
§       Real-Time (RT) systems are dedicated systems that need to adhere to deadlines, i.e., time constraints.
§       Correctness of the computation depends not only on the logical result but also on the time at which the results are produced.
§       Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems.
§       Real-Time systems may be either hard or soft real-time.




Hard Real-Time System

§       Must meet its deadline.
§       Conflicts with time-sharing systems, not supported by general-purpose operating systems.
§       Often used as a control device in a dedicated application such as industrial control and robotics
§       Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM).


Soft Real-Time System

§       A critical real-time task gets priority over the other tasks (Deadline desirable but not mandatory).
§       Limited utility in industrial control of robotics
§       Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.

Hand Held Systems


§       Personal Digital Assistants (PDAs)
§       Cellular telephones
§       Issues:
-      Limited memory
-      Slow processors
-      Small display screens.