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Computer system
Computer System
Book I: computer system fundamentals.
Chapter 1: INTRODUCTION TO COMPUTER.
Question 1. What is a computer?
A computer may be defined as a machine which accepts data from an input device, processes it
by performing arithmetical and logic operations in accordance with a program of instructions and
returns the results through an output unit.
A computer is basically an electronic machine operating on current.
Question 2. Components of a Computer system?
A computer system comprises of the following components:
1. Central Processing Unit (CPU).
- CPU is the heart of the whole sys
- CPU consists of the :
• control unit (CU)
• arithmetic logic unit (ALU)
• accumulator (ACC)
• program counter (PC)
1
I
N
T
E
R
N
A
L
• instruction register (IR)
• memory address register (MAR)
• memory data register (MDR)
• status register (SR)

• general purpose register
- The function of each components of CPU:
• Control unit:
 control and co_ordinate all hardware functions of the CS.
 examine and decode all program instructions to the computer and
initiate their execution by sending the appropriate signals.
• ALU:
 performs all arithmetic <addition, subtraction, multiplication,
division & exponentiation> and logic comparision two values
functions required by computer.
• ACC:
 holds the first operand of the temporary result of the ALU.
• PC:
 contains the add of the next instruction to be excuted.
• IR:
 contains the current instruction to be executed.
Main memory
• MAR:
 holds the address location to or from which data is to be transferred
• MDR:
 contains the data to be written to or read out of the addressed
location.
• SR:
 keeps track of the status of the accumalator.
• General Purpose Register:
 for general purpose procedures.
Please refer to diagram for an illustratin of the basic components of the CPU.
CPU

Control unit

Arithmetic Logic Unit
Accumulator
Program Couter to main
Instruction Register memory
Memory Address Register
Memory Data Register
Status Register
General Purpose Register
2
B
U
S
Basic components of a CPU.


Control Unit
Input Unit ALU Output Unit

Main Memory
Backing Storage
Control signals
Data flow
Components of a CS.
2. Input units
- Used to enter data( raw unprocessed facts) and instructions to the computer.
3. Output units
- Used for delevering the processed result from the computer in useful form.
4. Backing storage units
- Backing storage units need for high capacity data storage devices that can store
data in a more permanent form for later retrieral, updating and referencing.

- Backing storage is also called secondary storage external storage and auxiliary
storage.
Chapter 2: MICOPROCESSOR.
Question 1. Cache Memory?
- Cache memory is a small amount of very fast store with faster access time than
the main memory.
- Cache memory is used to temporaryty store data instructions that are likely to be
retrieved many times, thus speeds up the processing of data.
- Sits between main storage and the processor acting as holding area through which
all data and instructions pass.
- Old data in the cache memory is over written by new then cache is full.
Question 2. Virtual Memory?
- Virtual memory makes use of both the main memory and backing store.
- In a virtual memory sys, each user has the illusion that his program is in the main
memory all the time.
- The sys maintains this illusion by keeping some of the “unused” portion of the
program’s code and data on a backing store device which is usually magnetic disk
- The movement of the unused portion from the backing store to the mian memory
is transparent to the users.
- Please refer to diagram for virtual memory.
Backing Store Main Memory
3
A3
A1
A2
A3
Virtual Memory

Chapter 3: BATCH/ ONLINE AND REAL TIME PROCESSING SYSTEM.
Question 1. Batch Processing System?

- Def: Computer processing does not begin until all the input data has been
collected and grouped together called Batched Generally data is accumulated for a
certain period of time or unitl a certain quantity.
- Ads:
 Response time is not critical.
 Need to process large volumn of data.
 Computer efficiency is more important than response time.
- Dis:
 Time between recording and processing of source document is long
 Rereen normally required if errors are encountered.
 Data is not current.
 Error correction is more difficult.
Question 2. Online Processing System?
- Def: Inputs data enters the computer directly as soon as it is being transacted.
There information will be processed immediately and updated into the master file.
- Ads:
 Enter availability of information for decision making.
 More accurate data capture.
 Schedules suits user.
- Dis:
 CPU time is used less efficiently.
 Random arrival of transactions, terminal operator process each
transaction separately.
 More expensive than batch processing.
Question 3. Real Time Processing System?
- Def: One which controls the environment by receiving data processing them and
returning results sufficiently quickly to affect the functioning of the environment
at that time.
- Ads:
 Response time is very critical and sufficient quick.

- Dis:
 Expensive hardware & software.
 Very complex in terms of hardware & software.
Chapter 4: PRINTERS AND TERMINALS.
Question 1. Classification of printers?
1. Classifying printers according to speed.
a. Serial printers
Slow printers that print one character at a time.
Eg: Dot matrix printers
Daisywheel printers
b. Line printers
Medium to high speed printers that can print in excess of 2000 lines per minute.
Eg: Chain Printers
Band Printers
Drum Printers
2. Calssifying printers according to method of printing
a. Impact printers
Use hammers or prints to strike a print rebbon in order to form the character on the
paper.
b. Non impact printers
4
A2
A1
Use more silent methods of printing.
Eg: Thermal printers
Ink Jet printers
Lazers printers
3. Classifying printers according to print quality
Kinds of quality printers
Draft quality

Near letter quality(NLQ)
Letter quality
Graphic quality
Question 2. Describe some types of printer?
1. According to speed:
a. Dot matrix printer
- Serial impact printers that can print draft, near letter quality and a limited amount
of graphics.
- The print resolution is generally lower than lazer printers.
b. Daisywheel printers
- Are serial impact printers, the speed of a daisywheel printer is slow(20-55
characters per second), noisy in operation.
- The print head has the letters arranged at the end of spokes round a central hub.
c. Chain printers
- The chains printers has its characters set rapidly rotating on a print chain.
d. Band printers
- The band printer has rotating scalloped steel band.
e. Drum printers
- Are line printers, the print character are raised in bands around a heavy metal
drum which rotates at very high speed.
- The print hammers strike the paper and a print ribbon against an apropriate
character on the line. An entire line of the same character is printed on one
rotation of the drum.
f. Thermal printers
- Uses special heat sensitive paper and a matrix of print wires that become hot when
exposed to an electric current. The heated wires come into close contact with the
paper, burning the image of the character onto it.
- The more advanced thermal printers are using thermal transfer printing.
- They have a special heat sensitive ribbon and a print head with wires that become
hot when a currents is applied.

- The heat from the print wires causes the ink from the ribbon to fuse to a piece of
regular paper.
g. Inl Jet Printers
- The ink jet prints by using a small droplet generator to break special inks into tiny
drops, which are then forced towards a paper supply.
h. Lazer printers
- Using a photoconductive drum.
- A lazer is then used to write the image of the character onto the drum.
- After exposure to the lazer, the drum rotates through a developing station, picks up
toner and transfers it to the paper.
- The character is fused onto the paper by heat.
i. Ion deposition printers
- Ions are created in a cavity, and directed electrically through an orifice onto the
dielectric surface of a rotating cylinder.
- The required characters are formed as an electric charge image on the cylinders
surface.
- Toner is the applied to the charged image and transferred to the paper on which it
is transfixed by pressure(cold fusion).
j. Electrostatic printers
5
- Letterheads and logos are created electrostatically from a changeable metal
cylinder.
k. Magnetic printers
- A drum in the printer has a surface that can be coated with sows of tiny spots of
magnetion by means of thousands of minute recording heads.
- As the drum rotates it becomes covered with these magnetic spots so as to from a
latent image of the page to be printed.
- Dry ink particles are brought into contact with the drum’s surface and these
adthere to the magnetised spots. The ink was then pressunal on to the surface and
subsequently transferred onto the paper.

Question 3. Characteristics of a page printers?
- Speed
- Characters sets
- Copies
- Intelligence
- Output
Chapter 5: DATA STORAGE MEDIA.
Question 1. Data storage Requirements Characteristics?
- Low access time: fast speed
- Storage capacity: much enough
- Interchangeability: can be change easily
- Security: safe enough
- Transfer rate: fast enough
- Cost: economic
Question 2. Magnetic disks?
- This comprises a drive unit onto which one or perhaps two magnetic disk
cartridges are loaded.
- The drive consists of a control unit and a spindle housing that rotates continuously
when switch on.
- The cartridge are loaded by the operator so as to provide the data currently needed
for the job in hand.
- Bach tracks is devided up into sectors(often 4 or 8), sectors are read or written or
more at a time as blocks by means of a read.
- There are usually one head for each surface, all the heads are moved.
- Sunchronously across the tracks.
- Once in position all the data on the equiradial tracks can be read or written
without further movement of the heads.
- Cylinder is a set of equiradial tracks.
- A cartridge comprises several flat disks mounted on a central sprindle. When
mounted it rotates at a high speed enabling data to be read from or written to it.

The data is recorded magnetically on both surfaces of each disk in the form of
concertric tracks.
•
 Certain models of disk units also have a number of fixed read/write
heads in addition to the movable heads.
 The fixed head are positioned permanently over certain of the outer
tracks, there being one head per track, so climimating the need for
head movement.
- The heads are very close disk surface.
- Curshion of air carried by the rotating disk.
Question 3. Winchester disks( hard disks )?
- Comprises a number of platters(disks) permanently into an airtight enclosure.
- All dust is excluded thus perimiting the read/write heads to be positioned even
closer to the surfaces and so enabling greater recording densities to be employed.
6
- The disks have greater storage capacity and a higher rate of data transger.
- It has the lubricated surfaces allowing the heads “land” when the platters cease to
rotate, so eliminating head crashes.
- Winchester platters are either 14 in, 8 in, 5¼ in or 3½ in diameter.
Question 4. Floppy disks?
- Diskettes, generally called floppy disks, are single disks made of flexible plastic
and permanently housed is an envelope.
- The data on floppy disks is in concentric tracks on the outer part of the surfaces
and access to it is via slot in the envelope.
- The most common size are 3½ in, 5¼in, and 8 in diameter disks, the 3½ in disks
have the advantages of a shutter.
- Floppy disks may be either single or double sided and of course the drive needs to
be correspondingly equipped.
- Both the drives and the floppy disks themselves are inexpensive with the result
that they have come into extensive used by small business and home computer

buffs.
- The range of capacities is from 1/4 to 2 megabytes and transfer rates around 125
to 250 kilobytes per seconds.
Question 5. Optical disks?
- Optical disk are comparatively new development for data storage.
- Optical disks consist of a single removable glass, plastic or metal disk coated on
one side with tellurium and protected by a 1 mm layer or transpacent plastic.
- The disk diameters are mostly between 8 in and 14 in they rotate on a spindle in a
similar fashion to magnetic disks.
- The data is recorded in the form of minute pits burned into the telliurium coating
by a finely-focused lazer beam.
- Optical disks hold between 0.7 and GBs, this is about 20 times greater than
magnetic dis cartridges.
- The data is read by a low power laser beam which moved across the surface and is
reflected into a photo cell.
- Optical disks rotate mostly at 1500 r.p.m which, allowing for the movement of the
laser unti, given access time of between 16 & 500 ms and data transfer rates of 0.6
to 3 MVs per second.
- The draw back of optical disks is that the data cannot be erased so making them
non-rewriteable.
Question 6. Mass storage media?
- Mass storage media is a high capacity disk system as when necessary by
transferring data from a number of “data cartridges” house in cells.
- Each cartridge consists of a 3 in wide magnetic modium inside a protective cover
- In order to load the disk system, the data cartridges are moved automatically from
the cells.
- A typical system consists of 9440 cartridges giving a storage capacity of 472000
million bytes.
Question 7. Magnetic drums?
- A magnetic drum consists of a cylinder upon the surface of which data is stored in

magnetic form in tracks running around its circumference, each track has its own
read/write head.
- A typical magnetic drum has 800 tracks each capable of holding 5000 bytes.
Question 8. Charge_coupled Device Memory (CCD)?
- CCD consists of thousands tiny metal squares each capable of holding an electric
charge, thus representing a bit.
- The squares are in the form of an array 64 x 64 holding 4096 bits.
- It is very impact.
- CCD is volate lity storage.
Question 9. Magnetic Bubble Memory?
7
- A thin wayer of magnetic garnet is capable of containing tiny domains or
cylinders of magnetism, called bubbles.
- By erasing unwanted bubbles, the resultant presence of a bubbles represent a 1 or
a 0 bit.
- The main ads are low power consumption, compactness, robustness reliability and
non-volitility.
Question 10. Megnetic tape?
- The magnetic tape usage is now more as a backup medium rather than a primary
method of backing storage.
- It is often used as a depositony for disk dumped from fixed data storage.
- It is in reells of up 3600 feet and is made of Mylar plastic tape, 1/2 in wide and
coated with a magnetic material on one side.
- The data is read from one read and written to another.
- A reel of tape is loaded on a magnetic tape drive, and so as many drives are
needed as reels during a processing run.
- It is used as a backing medium than a primary method of backing storage.
- The seconds usually have to be sequence where store in magnetic tape.
Chapter 7: COMPUTER FILES.
Question 1. File Processes?

1. Sorting
a. The records in logical file are brought into some sequence as determined by key in
the records.
b. A computer is capable of sorting record into a “nested” sequence.
c. Sorting is done by a “sorting generator”. This is part of the computer’s software
and comprises several sophisticated sorting techniques that are called into use
according to the file and the sort requirements.
d. The need of sorting has dimished in line with the demise of magnetic tape as
backing storage.
2. Merging
- Merging implies that two or more files in the same sequence are combined into
one file.
a. File merging
 Two or more separate files of similar seconds and in the
same sequence are marged together so as to form one file.
b. Record merging
 The records from two or more “input” files, usually in the
same sequence, are combined one record in the output file.
3. Matching
a. Two or more input files (generally in the same sequence) are compared records
against record in order to ensure that there is a complete set of records for each
key.
b. Masmatched records are highlighted for subsequent action
4. Summanizing
a. Records with the same key in one file are accumulated together to form one
record in the output file.
b. Summanizing usually applies to a file presorted into a certain sequence and the
resultant file is in the same sequence.
c. Records to be summarized are generally of a similar type.
5. Searching

a. Searching is looking for records with certain keys or holding certain data and in
some way making a note of these.
b. An instance is a search for and count of all records with a debt balance of above a
certain amount.
6. Information retrieval
a. Information retrieval is the process that involves the bringing together of data
from several files.
b. Data may also be extracted from several files and combined before being
presented as information.
8
Chapter 8: DIRECT ACCESS FILE ORGANIZATION AND STRUCTURES.
Question 1. Storage and Access Modes?
There are 3 principal modes for storing and accessing accords on a disk or drum:
1. Serial mode:
- The record are stored contigously regardless of their keys
- The sole way of accessing serial seconds is to search through the complete file
starting with the first record.
- It is sometimes possible to partition a serial files thus reducing the search time by
starting the search at the beginning of a known partition.
- A serial file is normally of a temporary nature awaiting sorting into a useful
sequence.
2. Sequential mode:
- direct access sequential mode normally involves accessing sequential a file that is
stored sequentially.
- sequential mode is often associated with a master file held in a certain sequence
and updated by a transaction file sorted into the same sequence.
3. Indexed_sequential/ selective_sequential mode
- Indexed_sequential is a mode of storage where by records are held sequentially
and accessed selectively.
- Groups of unrequired records are skipped past.

- Indexed sequential files may also be accessed haphazandly.
4. Random modes:
- Each record is stored in a location determind from the second’s key by means of
an add generation algorithm.
- The only erricient way to find a record is to use the algorithm
- Random mode is applicable to master files
• Ads of random modes
 No index is required thus saving storage space
 It is a fast access method because little or no searching is involved
 Transaction do not need storing, thus saving time
 New records are easily insertly into the random file provided they
are not excessive in number
• Dis
 The main problem with the random mode is in achieving a uniform
spread of records over the storage are allocated to the file
Question 2. Direct Access Addressing?
- The key of record is used to identify by record
- The key of record also is used to decide its storage location(or address)
1. Self addressing:
- Self addressing is a straight forwards method because a record’s address is equal
to its key’s value
- The file is inevitably stored in key sequence
• Ads of self addressing
 It leads directly to the wanted record
 No indexing or searching is required
 The key itself need not necessarily be held within the stored
record- although it generally is
• Dis
 The storage space per second has to be the same
 When records one missing, storage locations related to its must be

left empty
2. Self addressing with key conversion
- This method a basically similar to self addressing except that the key required a
little processing to turn it into the record’s address
9
- This leads to either a pricise address
3. Matrix addressing
- In somes case, it is necessary to find the add of a record held within a multi
dimensional matrix of record it’s called matrix addressing.
Question 3. Direct Access Searching?
- Where as addressing determines the location of a record by using algorithmic
methods, searching finds the record by scanning groups of records, and index, or
both.
- ]The simplest method is to examine every record a file until the required record is
found a shortcut is generally desiable.
1. Indexed sequential searching
- A cylinder index is created to hold the highest cylinder’s key
- Associated with each cylinder is a block index holding the highest key in each
block within that cylinder
- When searching for a record’s key in the index
 The cylinder index is examined key_by_key until one is found that
is larger than or equal to the wanted key this directs the search to
the appropriate block index
 The block index a similarly examined and the search
 The block is searched record by record until the wanted record is
found
2. Binary searching( binary chopping )
- The key in the index to be binary search must be in sequence and form a complete
set
- The search starts at the midpoint of the index and then moves half way to the left

or right(down or up) depending upon whether are wanted key is less than or
greater than the midpoint key
- In pracice, the index is unlikely to as convenient as this example because it is not
always possible to exactly halve each sucessive move(complete exact holvingis
possible only when the total number of keys in the index is 2
0
-1)
- The average number of examinations comparisons is (log
2
k)
-1
( k is the number of
keys in the index)
3. Block searching
- A block is a subdivision of an index. A block is devised to contain, roughly the
square root of the number of keys in the whole index
- The search is first through the block index to find the appropriate block and then
through this to find the wanted key
- The average number of examinations is square – root –
k
(k is the total number
of keys)
4. Balanced binary tree searching
- A binary tree is a relationship of keys such that the examination of any key leads
to one of two other keys
- The binary tree is actually in the form of an index containing all the keys together
with a directory showing the braches stemming left and right from each key
- Binary tree searching is suitable for an unsequenced file
- The search is similar to binary searching in that each key examination holves the
rinaining keys, on average

Chapter 11: INTRODUCTION TO ARTIFICAL INTELLIGENCE.
Question 1. AI?
Atificial Intelligence
It has three braches
1. Expert systems (or knowledge- base system)
- ESs are programs that contain the knowledge of human expert, encoded so a
computer can understand it with encated- knowledge seasoning machinism, ES
can tackle problem that are beyond the seach of conventionally programmed
computers.
10
2. Natural language systems (everyday native language)
- Natural language systems are programs that understand the native language of the
user, such as E
- The most popular natural language systems are those that act as interfaces to data
bases
3. Simple perception systems (for vision, speed and touch)
- They can interpret visual scenes and decide if object meet inspection standards
and quality control criteria, or move a robot to the proper location ot grasp a part
for manufacturing
Question 2. Who does the updates?
- Updating the knowledge bases is very diffirent when with updating databases
because of the difference in the type of information and in the cause and effect
relationship contained in knowledge bases
- A knowledge in the area, when databases may be modified by a normal users
Chapter 12: EXPERT SYSTEMS.
Question 1. What is an ES( Expert system )?
An ES is a knowledge-intersive program that solves a problem that normally requires human
expertise
• Characteristics of ESs
- They solve problems as well as or better than human experts

- They use knowledge in the form of rules or frames
- They can consider multiple hypotheses simultaneouly
• Types of ES
- An assistant
 Is the leasts expert or lowest level ESs
 It helps a decision maker by doing routine analysis and porting out
those portion of the work where human expertise is required
- A colleage
 The new discusses the problem until a joint decission is reached
 When system is going wrong, the user adds more information to
get it back on track
- True ES
 Is a system that advises the user without question
 There are no practical areas today in which decission
Question 2. A ES Life Cycle (ESLC)?
- An accepted SDLC for expert systems has yet to be developed
There are 6 phases life cycle in an ES
1. Phase1 – Selection of an Appropriate Problem
- Phase 1 involves finding an appropriate problem for an ES, indentifying an expert
to contribute the expertise
- Establishing a preliminary approach
- Analysing the cost and benefitsPreparing a development plan
2. Phase 2 – Development of a prototype system
- A prototype sys is a small version of an ES designed to test assumptions about
how to encode the facts, the relationships and the knowledge of experts
- The prototype permits the knowledge engineer to gain the expert’s commitment
and to develop a deeper understanding of the field of expertise
- Other subtasks in this phase:
 Learning about the domain and the task
 Specifying performance criteria

 Selecting an ES building tool
 Developing an implementation plan
 Developing a detailed design for a complete system
3. Phase 3 – Development of a Complete System
11
- The main work in this phase is the addition of a very large number of rules
- The knowledge base has to be expanded to full knowledge base appropriate to the
real world and the user interface has to be developed
2. Phase 4 – Evaluation of the system
- This phase involves testing the system against the performance establised in
earlier stages
5. Phase 5 – Intergration of the system
- The ES has to be intergrated into the data flow and work patterns of the
organization
- In this stage, the expert system has to be interfaced with other databases,
instruments and hardware.
6. Phase 6 – Maintenance of the system
- The maintenance of the ES involves is updating, charging in the system when
operating. When operating, more problems occur in the system, so it is necessary
to continue take care the system by expert in a fix period of time
- So expert system, are so complex that in a few year the maintenance costs will
equal the development costs.
BOOK II: Computer systems architecture.
Chapter 1 – 2: NUMBER BASES.
Question 1. Common number bases used in computer hardware operation?
• Decimal(denary) system:
- The base is ten – there are 10 different symbols, the digits 0, 1, 2, etc upto 9
- To represent value less than ten involves only one digit larger values need two or
more digits
• Binary system

- The base must be two, with only the digits 0 and 1 available
- To show values of two or ever require two or more binary digits
• Octal system
- Octal system has eight as its base, it uses the symbol 0, 1, 2 up to 7 only
- Two or more digits are needed for values of eight and above
• Hexadecimal system(hex)
- Hexadecimal system has sixteen as its base, it use the symbols 0, 1, 2 ,9 & A, B,
C, D, E, F, to stand for the “digits” ten, eleven, twelve, thirteen, fourteen, fifteen.
Question 2. Converting from Bases To Bases?
1. Change the decimal
- Binary:
Eg. (2559) 10
2559 1
1279 1
639 1
319 1
159 1
79 1 (2559)
10
= (10111111111)
2
39 1
19 1
9 1
4 0
2 1
0 0
- Octal:
7690 8
49 96,1 8

10 16 120 8

40 15 8

12
2 1
0
7 1
1

(7690)
10
= (17012)
8
- Hexadecimal:
6396 16
159 399 16
156 79 24 16

C F
(6369)
10
= (CF81)
16
2. Convert to others from binary
- To decimal
(101010)
2
(?)
10

1.2
5
+ 0.2
4
+ 1.2
3
+ 0.2
2
+ 1.2
1
+ 0.2
0
= 42
(101010)
2
= (42)
10

- To octal
100101101
 1
st
step change into denary
= 1.2
8
+ 1.2
5
+ 1.2
3
+ 1.2

2
+ 1.2
0
= 256 + 32 + 8 + 4 + 1
=(301)
10
 2
nd
step: convert to octal
301 8
61 37 8

(301)
10
= (455)
8
(100101101)
2
= (455)
8
- To hexadecimal
110111011011
1
st
step
= 1.2
11
+ 1.2
10
+ 1.2

8
+ 1.2
7
+ 1.2
6
+ 1.2
4
+ 1.2
3
+ 1.2
1
+ 1.2
0
= 2048+ 1024 + 256 + 158 + 64 + 16 + 8 + 2 + 1
= (3547)
10

2
nd
step
3547 16
384 221 16
27 61
(3547)
10
= (CCA)
16
(110111011011)
2
= (CCA)

16
3. Convert into binary and display the answer in normalized exponential form
247 1
123 1
61 1
30 1
15 1
7 1
13
1
2
2
1
1
5
8
1
1
1
5 5
4
1
1
1
3
1
3
3 1
1 1
0 1

(247)
10
= (11110111)
2

= 0. 1111011 x 2
normalized exponential form
Question 3. Integer and Floating point arithmetic?–
1. Floating – point Addition
a. (0.1011 x 2
5
) + (0.1001 x 2
5
)
= (0.1011 + 0. 1001) x 2
5
= 1.0100 x 2
5
= 0.10100 x 2
6
b. (0.1001 x 2
3
) + (0.1110 x 2
5
)
= (0.001001 x 2
5
) + (0.1110 x 2
5
)

= (0.001001 + 0.111000) x 2
5
= 1.000001 x 2
5
= 0.1000 x 2
6
(here have truncation)
(0.1000001 x 2
6
)
2. Floating – point subtraction
a. (0.1110 x 2
7
) – (0.1100 x 2
7
)
= 0.0010 x 2
7
= 0. 10 x 2
5
b. (0.1001 x 2
8
) – ( 0.1000 x 2
5
)
= (0.1001 x 2
8
) – ( 0.0001 x 2
8
)

= 0.1000 x 2
8
3. Floating – point multiplication
a. (0.1010 x 2
3
) x (0.1100 x 2
3
)
= (0.1010 x 0.1100) x 2
6
= 0.01111 x 2
6
= 0.1111 x 2
5
b. (0.11110 x 2
3
) x ((0.01011) x 2
4
)
= (0.11110 x 0. 01011) x 2
7
= 0.001111 x 2
7
= 0.1111 x 2
5
4. Floating – point division.
a. (0.11010 x 2
6
) : (0.001 x 2
6

)
= (0.11010 x 2
6
) : (1 x 2
3
)
= 0.1101 x 2
6
: 1x 2
3
= 0.1101 x 2
3
b. (0.110111 x 2
6
) : (0.1001 x 2
4
)
= (0.110111 : 0.1001) x 2
2
= (1101.11 : 1001) x 2
2
= 1.100001 x 2
2
= 0.1100001 x 2
3
Chapter 3: TYPES OF INSTRUCTION AND ADDRESSING.
Question 1. Types of instructions used in CS?
1. Arithmetic instructions.
Arithmetic instructions include directives to the computers to perform additions, subtraction,
multiplications, divisions and exponentiations.

2. Input/ output instructions.
They direct the computer to read data values from the specified input devices into the main
store for processing.
They also include instructions to write the contents of memory locations holding the result of
processing to a specified output device.
3. Decision or control instructions.
Most data processing application will contain situations where alternative calculations or
procedures will have to be executed based on the result of condition tests carried out.
4. Data handling instructions
They include the copying of the content of one memory location to another or setting a
memory locations to an initial value.
Also include the management or insertion of characters into data items
14
Examples of such instructions include branch instructions, jump instruction & stop
instruction.
Question 2. Types of addressing?
1. Direct addressing
The operands of each machine instructions is used to retrieve the data
2. Indirect addressing
The operands is used to specify the memory address which contains the address of the data to
be processed
Op – code
OP – CODE OPERAND OP – CODE OPERAND
12345
Data item
12345
Data item
Main storage
Direct addressing
Indirect addressing

3. Indexed addressing
- The main applications of this type of addressing technique is to enable to access of
sequential locations in memory that are adjacent to each other
- Each adjcent memory address has value n+1, where n is the address of the
previous location
- When the first of the location have been accessed, the next memory location in
sequence is accessed by simply increasing the add of the present location by 1 &
using accessing it
- The starting address of the series of locations is specified in the operand of the
instruction
- In order to access the next location in sequence, the content of the index register is
increased by 1 a added to the opreand address
- This is done repeatedly until the last memory location in the series is processed
Indexed addressing.
OP – CODE OPERAND

Index Register
Chapter 4: PROGRAMMING LANGUAGES.
Question 1. Program and level of language?
Program is group of constructions that is linked together to perform specific task. It’s
necessary for a computer program to be written in a “PL” because at a computer program is
created by a programing using a sys analyst’s specification of the job in the hand.
1. Machine language
- ML is the set of bit(0,1) that can performed considered by CPU
- Ads
 fast
 short prog
 store in small memory
- Dis
Data 1 Data 2 Data 3 Data 4

15
 difficult to understand & remember its code
 takes a lot of time to programming
 difficult to use
2. Low level language
- LLL is used to dercribe exactly procedure of performance of CPU at certain time
- Features:
 Instruction is written by natrural English or natural language
 More powerful and so the prog is shortest
 Need less instruction
 Is a one to one relationship between the written instruction and the
machine instructions
 It’s instruction tend to be machine. It runs in OS
- Ads:
 Easy to write
 Easy to understand
 Known the processing data in CPU
 Prog writing is shortset
- Dis:
 Must be complier
 The time of running prog is longer than machine language
3. High level language
- HLL was developed in order to further easy the work of programmers by making
the programming language more procedure oriented
- Features:
 The statements of HLL are closer to natural english or other natural
language
 A HLL source program must be translated into machine code by
means of a compiler or an interpreter
- Ads:

 Easy to wirte
 Easy to understand
 May be used for everybody
 Closed to natural languages english language
- Dis:
 Must be interpreter by compiler or an interpreter before processing
by the computer
 The prog is long
 The time to run the prog is longer than low level language
Question 2. Some High Level Languages (HLL)?
1. COBOL: Common Business Oriented Language
- COBOL is an exetensively used HLL and since around 1960 several versions have
appeared
- The original intention was that COBOL should be capable of being compiled and
run on any model of computer
- COBOL is now employed for many business data processing applications, and so
a brief explaination of its structure follows
- A COBOL program consists of 4 divisions:
 Identifycation division this identifies the prog
 Enviroment division specifies the computer to be used for
compiling and processing
 Data division specifies the format and relates to these to the names
used in the procedure division
16
 Procedure division comprises the statements in the source program,
this is the main part of a COBOL program
2. BASIC: Beginners ALL purpose Symbolic Instruction Code
- BASIC is a straightforward HLL intended for use in a time-sharing environment in
this respect it is particularly beneficial in educational institutions
- One of the difficulties with BASIC is the welter of dialects currently in use

- Essentially BASIC consists of statements made up of verbs & variables. The verbs
are similar to those in COBOL but there is a large to them that in effect become
the addresses of their locations in the main store
- A variable name must be unique and generally consists of one or a few alphabetic
characters, purhaps followed by a digit
3. PASCAL: named after the famous 17
th
century French mathematician
- It was expressly designed as a language to make programming more systematic
and discriplired and in these respects lends itself to structured programming
- It is however more difficult to learn than are COBOLS BASIC and so is unliked to
be accepted as a language for microcomputers are geared to BASIC only
Question 3. Operating Systeim?
- Concept of OS:
 An OS consists of a suite of programs, one of which, the master,
kernel or exeactive program, remains resident in the main store.
This program controls the other OS programs in th suites and
between them they controls the application programs
 Often the operating system includes various application packages
among its suit of programs. Ex of such software include: word
processing, electronic mail, networking, speadsheet, graphics and
file handling
- Function of OS
 Pricrity assignment:
Jobs waiting execution are scheduled according to either a predetermined or a dynamic
assignments plan
 Control of multiprogramming
Control of accomplish multiprogramming an “executive” or “supervisor” program is
employed to control the application programs
 Communication

Control of data transmission between terminals and the computer, and computer to
computer
 Database
Control of DBMS
 Software control
Control of assemblers, compilers, utility software, and subroutines so that these are
imediately available when required
 Spooling
The control of input/output peripherals in order to achieve their best utilisation
 Dynamic allocation
Of main and backing storage, including virtual storage
 Operating allocation
Via the console printer or VDU
 Debugging and editing new programs
In confunction with the compiler, and passing error msgs to the user
 Operation log
Maintaince of details of all jobs carried out by the computer
 Application package control
Especially with microcomputers, as describe above
Chapter 6: TRANSLATORS.
Question 1. Translators?
1. Assemblers
17
• Def: A program that translates assembly language into machine code. Dos machine
instruction is generated for each source instruction
- The resulting program ran only be executed when the assembly process is
completed
• Operation:
- Translates mnemonic operation codes into machine code & symbolic address into
machine address

- Includes the neressary linkages for closed subroutines and inserts appropriate
machine code for macros
- Allocates area of storage
- Detects and indicates valid source language instruction
- Procedures the object program on tape or disk required
- The lesting may also include error codes if appropriate. To illustrate the methods
used just think about an assembly program. We must first look at the directives
 A directive is used to control the assembly process, it is not
asembled but is obeyed by the assembler when it is encouteded, e.g
”END”, is sometimes called a pseudo-operation code on pseudo-
opcode
2. Interpreter
A program which translates and executes each source statement in logical sequence as the
program one instruction at a time, completely translating and executing each instruction before it
goes onto the next
- Interpreter, which deals with the source program one instruction at a time,
completely translating and executing each instruction before it goes onto the next
- Interpreter seldom produce object code but call upon inbuilt routines instead
- Some intermediate code is usually produced tempororily
- If an interpreter is used, the source program will be translated every time the
program is executed
- Interpreters are widely used, particular for the programming language Basic on
small computers
• Interpriter are used for such things as:
- Handling user commands in an interactive sys
- Debugging programs as they run
- Handling software produced for or by a different computer
3. Compilers:
A program that translates HLL into a machine orientated language, often the machine code.
Many machine instructions are generated for each source statement

- The compiler:
 Translates the source program statements into machine code
 Includes linkage for closed subroutines
 Allcocates areas of main storage
 Generates the object program on cards, tape and disc as required
 Produces a printed listing of the source and objected programs
when required
 Tabulates a lish of errors found during compilation
- Compilers are commonly used for the translation of HLL program
- Compiler translates the whole of the HLL source program into a machine code
object program prior to the program being loaded into main memory and executed
- If a compiler is used, the same program need only be translated once
• Stages of compilation
 lexical analysis
 systatical analysis
 code generation
18
Chapter 7: SOFTWARE.
Question 1. Application software?
- Application software comprises the programs that are written specifically to
achieve resulting appertaining to the company’s activities
- Application software comes from two source
 They produce by themselves
 Buy from an external agency
1. Ads and dis of using application packages in house
• Ads
- The requirements of the application are more easily met
- There is more control in testing and debugging
- The more control over the usage and support obtained
• Dis

- There is a waiting period before the application can be implemented
- Development cost is higher than buying a package
2. Ads and dis of using application package
• Ads:
- The packages can be used immediately
- Documentation is generally good
- It can be used on a varisty of machines
- It is cheaper as the costs of the packages are shared between many users
- Comprehensive on line help information and guided tutorials available
- Easily remembered command syntax
- Can be used in confunction with other software in an integrated fashion
• Dis:
- Modifications may be difficult for some applications
- Package may be two generalized to suit user needs
- Some features purchased may not be required
- Support given depends on stability and professionalison of the vendor
- User are required to comply with the owner’s regulations
Question 2. Utility software?
- Certain processing is common to a high proportion of computer users, and so
utility software has been created to cater for this need
- Utility software is intended to be sufficiently flexible to meet most user’s
requirements and is tailored to meet their precise needs by means of parameter
entered prior to use
- Some of the utility programs described below may be incorporated into the OS
that is used with a particular computer
 File conversion: this convers the transference of data from any
medium to any other
 File copying: an exact copy of a data set is made on to another lot
for the same type of storage medium
 File reorganisation: direct access, files over flow records are stored

in designed blocked, this is acceptable up to a point but from time
it si necessary to reorganise the file so as to remove the overflow
 File maintenance(amendment): this procedure involves the
straightforward insertion and deletion of records into or form
sequential files
 Sorting: is frequently necessary in order to arrange a set of records
into a certain sequence based on their key values
 Dumping routines: a dump routine is used in confunction with a
restfirt program
19
 House keeping operations: there are programs or parts of a
programs not directly concerned with the solution of the problem in
hand
 Trace routines: these entails, the dumping, display or printing of th
program or other contents of the main store during program testing
to facilitate error detection
- Utilitys are commonly used to perform these functions:
 Copying of files
 Sorting of data
 Merging of files
 Data recovery
 Reformating of records by reamanging their fields
 File reorganization
 Reporting of sys status and usages
Question 3. System software?
There are three main types of memory placement policy:
- First fit
- Best fit
- Worst fit
1. First fit policy, an incoming job is placed in the first available free space large enough to

fit it. This allows the placement decision to be made quickly
2. Best fit policy, an incoming job is placed in the free space in which it fits most tightly
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 and
thus free up a portion memory

- Virtual storage systems have evolved to meet these needs. Virtual storage systems
allow programs to be as large as necessary, even larger that the physical storage
capacity of the computer
20
- Translating the user’s view of the program into the physical reality of computer
storage is one of the major task performed by virtual memory OS like IBM’s MVS
and digital VMS
- Virtual storage system included non paged systems
Paged systems
Chapter 9: NETWORKING.
Question 1. Types of network layout?
Network topology is the name given to the various types of network layout
1. Start network(or centralised network)
- This network all communications go through a central node
Node A
Node D
Central(Hub) active
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
- Work stations connect to the ring
- More cabling requiring than BUS
- The connectors used with a lot of problem
- Cable is used UTP, STP
4. Bus network( or multidrop network)
A B
- All workstations are connected the same cable segment
- Commonly used for implomenting ethenet at 10 mbps(Mb/s)
- The cable is terminalled at each end
21
- Writing is normally store point to point
- A faulty cable or work station will take the entire LAN down
Question 2. Network control?
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

This method allows for transmission in one direction only
b. Half duplex transmission
This method means that’s data can be transmitted in both directions, but is only on direction at a
time
c. Full duplex trasmission

This method of transimission allows for transmission in both directions simultaneously
* Two modes of transmission are used when transmitting data over communication lines.
They are
 asynchrorous
 synchronous
Asynchronous:
- One character at a time is transmitted or received
- Each character is preceded by a start bit and a stop bit
 The start bit is used to indicate or character is being sent
 The stop bit is used to indicate the end of the character
- Asynchronous transmission is used for low speed devices
Direction of transmission
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
22
Computer
Computer
Modem
Modem
- 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
- Proprietorship by a single organisation
• Features:
- LAN is after used in offices & it connects of fire equipment to provide a variety of
data communication. Service with light transmission rate and low errors rate
- The majorities of LANs are connected by coxial cable, and the protocol(rule for
communication) is very simple
• Three other important aspects of LANs:
- Acess method (protocol)

Central control
CSMA_CD
Empty slot access
Token access/token passing
• LAN transmission modes:
There are 2 main types of LAN transmission modes
a. Baseband transmission: is essentially & binary method, each bit being
represented by one of two states of an electric pulse passing through the network.
Baseband is nevertheless suitable for most LANs, and is the mode employed by
Ethernet and Cambridge Ring network
b. Broadband transmission: the data is modulates into a carrier wave. Broadband
transmission has a much greater band width than baseband, it can transmit sth
like ten times as much in a given time
• LAN is one of the distributed processing designs
- LAN are considered loosely coupled system processors are located in separate
machines and communicate at relatively low speeds
- LAN is the means by which distribution takes places, regardless of what are
distributed
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
7. Distributed data processing sys is one of which interconnected points at which processing
power and storage capacity are availble
Question 2. Fibre Optics?
23
• Fibre optics is that data and other information is transmitted in the form of light through
very fine glass fibres
• Ads:
- High bandwidth eg data transmission capacity
- Low cross – talk eg interference between adjacent fibres
- Low attenuation eg loss of signal strength
- Freedom from interference from external electrical and electromagnetic
equipment
- High reliability
- Safe because no heat, sparks or electrical voltages are created
- Economic because glass is loss expensive than copper
Chapter 11: DISTRIBUTED PROCESSING.
Question 1. Client/ Server Model?
- It’s common way to employ distributed processing that is client/server architecture which
splits into components
- Server store & main palates the actual data & provide secenity, losting function
transaction logging recovery capabilities
- Client/ server model seems like PC lan each server support more users
- Data request in form of SQL(structure quenf language) command travel across the
network from client to server
Client Server Database
Request

LAN Response
Question 2. File sharing VS client server?
Network


Client Server
The file sharing model

<< Continuousting to page 28>>


Network

Interface Interface
The client/ server model
24
Application
tool process
Application
tool process
Database
Application tool
process
Database
engine process
Database
Database
engine process
SQL execute
commands

File sharing
- File are shared for a lot of machines
in the network(each machine can
access to the shared files)
- It can create heavy network
traffic(each access to a large file can
potentially block of the file, showing
the system amount of information
temporarily unavailable to other user)
Client server
- Database are stored in the server
machines and client machines
can send request for appropriate
data
- Only the records matching the
request criteria raresent back to
client machines so the sys never
has heavy traffic
Question 3. Distributed Database Topology?
- With distributed processing system, user can access data, that is located among a number
of physically separate servers. It provides user with a globol view of the data.
- With distributed database, the problems with implementing still exists.
- Developing distributed database application requires extensive planning to anticipate the
many complex possibilities.
- For a large number of transactions travelling across the network the capacity of
communication lines and the possible impact a system must be carefully considered.
Chapter 12: THE TCP/IP PROTOCOL SUITE.
Question 1. The OSI model? <Open System Interconnection>
- OSI model, adopted in 1983 by IOS <International Organization Standardization>, which
is a framework for defining standards for linking hetenogenerous computer

- The communication function are pastitioned into a vertical set of layers. Each layer
performs are lated subset of the functions required to communicate with other sys
- The OSI layers
 Physical: concerned with transmission of unstructured bit stream
over physical medium, deals with the mechinical, electrical,
functional, and procedual characteristrics to access the physical
medium
 Data link: provides for the reliable transfer of information across
the physical link, send blocks of data with the necessary
synchronization, error control, and flow control.
 Network: provides upper layers with independence from the data
transmission and switching technologies used to connect systems,
responsible for establishing, maintaining and terminating
connections
 Transport: provides rediable, transparent transfer of data between
end points, provide end_to_end error recovery and flow control.
 Session: provides the control structure for communicaton between
applications, establishes, manages, and terminates connections
between cooperating applications.
 Presentation: provide independence to the application processes
from difference in data representation(syntax)
 Application: provide access to the OSI environment for users and
also propvides distributed information services
User oriented Application Users of transport
Presentation service
End to end Session
connection oriented Transport
Network
Point to point Data link Network service
link oriented Physical

Perspectives on the OSI architecture
Question 2. Protocols?
Both OSI and the TCP/IP protocol suite deal with communications among hetrnogenerous
computers
Both are based on the concept of protocol and have many similarities
a. TCP/IP protocol architecture
25