3. Worst fit policy, an incoming job is placed in the largest possible hole of free
space
Question 4. Types of scheduling?
- Scheduling of job is also an important part of any OS. It involves keeping
track of and deciding which job is to be executed
- Types of scheduling
 Deadline scheduling
 First in first out scheduling(FIFO)
 Round robin scheduling
 Shortest job first(STF) scheduling
 Shortest remaining time scheduling(SRT)
- More details about types of scheduling
 In deadline scheduling certains are scheduled to be
completed by a specifir time or deadline. Deadline
scheduling can be very complex requiring substantial
overhead in resource management
 FIFO scheduling: processes are dispatched according to
their arrival time in the ready queue. This type of
 Round robin scheduling is similar to FIFO scheduling but
the difference lies in that each job is given a slice of CPU
time
 SJF scheduling: shorter jobs are more favoured than longer
one. SJF selects job that ensures the next jobs will complete
& leave the sys as soon as possible
 SRT scheduling: the job will the smallest estimated
remaining run time is executed first. In SRT, a running job
may be replaced by a new job with a shorter estimated run
time
Chapter 8: MEMORY MANAGEMENT.
Question 1. Virtual Storage System?
- Instructions and data not currently needed might even be stored on the disk

V
i
e
w
e
r
w
w
w
.
d
o
c
u
-
t
r
a
c
k
.
c
o
m
Click to buy NOW!
P
D
F
-
X

m
Passtive
Node C
Node B
- The centra of star network is the hub which performs the function of
routing msgs and data within the network
- The hub manages & senvices all incoming and outgoing communication
traffic. It’s also provide info services from a large central data bases
2. Mesh network (or distributed network)
- This network may be fully connected or partially connected
A E B
D C
- Data can get from one node to another node via different route
- Multi point to point
3. Ring network( or loop network)

A B
D C

e

V
i
e
w
e
r
w
w
w
.
d
o
c
u
-
t
r
a
c
k
.
c
o
m
Click to buy NOW!
P
D
F

c
o
m
1. Modems(modulation demodulation)
A telephone line B

Modem modem
Digital signal analog signal
OR
Data transmission Using a Modem
- To communicate between computers via telephone line, there is a need to
convert signals from the computer into a form suitable for transmission
over the telephone line or convert from digital signals into analogue
signals, and convert back from analogue signals to digital signals
- From source: digitals signals are converted into analogue
signals(modulation)
- At the received end analogue signals are converted back into digital
signals (demodulation)
- A device to handle modulation, demodulation process is called Modem
2. Bandwidth and Fibre Opties
The major benefits of fibre opties are:
- Fibre optic cables are much lighter and smaller in size
- Greatly increased speed in data transmission
- Greatly reliability
- Greater secerity as lines can not be tapped
3. Transmission
a. Simplex transmission

F
-
X
C
h
a
n
g
e

V
i
e
w
e
r
w
w
w
.
d
o
c
u
-
t
r
a
c
k

u
-
t
r
a
c
k
.
c
o
m
S S S S
T T T T
A 11000001 O 1111111 A 11000010 O
R P R P
T T
Synchronous:
- The speed of transmission is much faster
- Transmission groups of character can be send down the line without the
start and stop bits
Direction of transmission

000111000001011100000011
Question 3. LAN_Local Area Networks?
 Def: A LAN is a communication network in that connects office
equipment to provide a variety of data communication service which
features high transmission rates and low error rates
 Characteristics:
- Utilisation of some type of switching topology
- Locality restricted to a few miles or in the same bulding

D
F
-
X
C
h
a
n
g
e

V
i
e
w
e
r
w
w
w
.
d
o
c
u
-
t
r
a
c

c
u
-
t
r
a
c
k
.
c
o
m
Chapter 10: DATA COMMUNICATIONS.
Question 1. Write a short note of?
1. Communication is an extensive subject in its own right, encompassing not only
data transmission but also sound and video transmission via telephone lines, radio
links and satellite links.
2. Multiplexing is a means of combining together data from several sources so that it
can be transmitted along one comminication line
3. Front – end processing: A front – end processor is usually a minicomputer or a
microcomputer interposed between the main computer and the multiplexor
Its purpose is to relieve the host computer from the bunden of communications
housekeeping
4. Concentrators are device used to gather the bit from each terminal or group of
terminal and hold them on buffer store unit until there are sufficient to justify
forward transmission
5. Protocol is an “agreement” where by devices can communicate is a fully
understand manner
6. Multidrop line<multipoint line> has several terminals on concentrator attached to
it

P
D
F
-
X
C
h
a
n
g
e

V
i
e
w
e
r
w
w
w
.
d
o
c
u
-
t
r
a

o
c
u
-
t
r
a
c
k
.
c
o
m