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Control Unit Input Unit ALU Output Unit Main Memory Backing Storage Control signals Data flow... - Backing storage units need for high capacity data storagedevices that can store data

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 inputdevice, processes it by performing arithmetical and logic operations inaccordance with a program of instructions and returns the results through anoutput 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 :

 program counter (PC)

 memory data register (MDR)

 general purpose register

- The function of each components of CPU:

 ALU:

 performs all arithmetic <addition, subtraction,multiplication, division & exponentiation> and logiccomparision two values functions required bycomputer

 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

Memory Address Register

Memory Data Register

Status Register

General Purpose Register

Basic components of a CPU

Control Unit Input Unit ALU Output Unit

Main Memory

Backing Storage

Control signals Data flow

- Backing storage units need for high capacity data storagedevices that can store data in a more permanent form for laterretrieral, updating and referencing.

- Backing storage is also called secondary storage externalstorage and auxiliary storage

Chapter 2: MICOPROCESSOR.

Question 1 Cache Memory?

- Cache memory is a small amount of very fast store with fasteraccess time than the main memory

- Cache memory is used to temporaryty store data instructionsthat are likely to be retrieved many times, thus speeds up theprocessing of data

- Sits between main storage and the processor acting as holdingarea 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 andbacking store

- In a virtual memory sys, each user has the illusion that hisprogram 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 devicewhich is usually magnetic disk

- The movement of the unused portion from the backing store tothe mian memory is transparent to the users

- Please refer to diagram for virtual memory

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 datahas 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 responsetime

- Dis:

 Time between recording and processing of sourcedocument 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 isbeing transacted There information will be processedimmediately 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 operatorprocess each transaction separately

 More expensive than batch processing

Question 3 Real Time Processing System?

- Def: One which controls the environment by receiving dataprocessing them and returning results sufficiently quickly toaffect 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

2 Calssifying printers according to method of printing

a Impact printers

Use hammers or prints to strike a print rebbon in order to form thecharacter on the paper

b Non impact printers

Use more silent methods of printing

Eg: Thermal printers

Ink Jet printersLazers printers

3 Classifying printers according to print quality

Kinds of quality printersDraft 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

f Thermal printers

- Uses special heat sensitive paper and a matrix of print wires thatbecome hot when exposed to an electric current The heatedwires come into close contact with the paper, burning the image

of the character onto it

- The more advanced thermal printers are using thermal transferprinting

- They have a special heat sensitive ribbon and a print head withwires that become hot when a currents is applied

- The heat from the print wires causes the ink from the ribbon tofuse to a piece of regular paper

g Inl Jet Printers

- The ink jet prints by using a small droplet generator to breakspecial inks into tiny drops, which are then forced towards apaper supply

h Lazer printers

- Using a photoconductive drum

- A lazer is then used to write the image of the character onto thedrum

- After exposure to the lazer, the drum rotates through adeveloping 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 anorifice 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 thepaper on which it is transfixed by pressure(cold fusion)

j Electrostatic printers

- Letterheads and logos are created electrostatically from achangeable 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 minuterecording heads

- As the drum rotates it becomes covered with these magneticspots so as to from a latent image of the page to be printed

- Dry ink particles are brought into contact with the drum’s surfaceand these adthere to the magnetised spots The ink was thenpressunal on to the surface and subsequently transferred ontothe paper

Question 3 Characteristics of a page printers?

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 twomagnetic disk cartridges are loaded

- The drive consists of a control unit and a spindle housing thatrotates continuously when switch on

- The cartridge are loaded by the operator so as to provide thedata currently needed for the job in hand

- Bach tracks is devided up into sectors(often 4 or 8), sectors areread 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 aremoved

- 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 centralsprindle When mounted it rotates at a high speed enabling data

to be read from or written to it The data is recordedmagnetically on both surfaces of each disk in the form ofconcertric tracks



 Certain models of disk units also have a number offixed read/write heads in addition to the movableheads

 The fixed head are positioned permanently overcertain of the outer tracks, there being one head pertrack, 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 anairtight enclosure

- All dust is excluded thus perimiting the read/write heads to bepositioned even closer to the surfaces and so enabling greaterrecording densities to be employed

- The disks have greater storage capacity and a higher rate ofdata transger

- It has the lubricated surfaces allowing the heads “land” when theplatters cease to rotate, so eliminating head crashes

- Winchester platters are either 14 in, 8 in, 5¼ in or 3½ indiameter

Question 4 Floppy disks?

- Diskettes, generally called floppy disks, are single disks made offlexible 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 coursethe drive needs to be correspondingly equipped

- Both the drives and the floppy disks themselves are inexpensivewith the result that they have come into extensive used by smallbusiness and home computer buffs.

- The range of capacities is from 1/4 to 2 megabytes and transferrates around 125 to 250 kilobytes per seconds

Question 5 Optical disks?

- Optical disk are comparatively new development for datastorage

- Optical disks consist of a single removable glass, plastic or metaldisk coated on one side with tellurium and protected by a 1 mmlayer 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 thetelliurium coating by a finely-focused lazer beam

- Optical disks hold between 0.7 and GBs, this is about 20 timesgreater than magnetic dis cartridges

- The data is read by a low power laser beam which moved acrossthe surface and is reflected into a photo cell

- Optical disks rotate mostly at 1500 r.p.m which, allowing for themovement 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 whennecessary by transferring data from a number of “datacartridges” house in cells

- Each cartridge consists of a 3 in wide magnetic modium inside aprotective cover

- In order to load the disk system, the data cartridges are movedautomatically from the cells

- A typical system consists of 9440 cartridges giving a storagecapacity of 472000 million bytes

Question 7 Magnetic drums?

- A magnetic drum consists of a cylinder upon the surface of whichdata is stored in magnetic form in tracks running around itscircumference, 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 ofholding an electric charge, thus representing a bit

- The squares are in the form of an array 64 x 64 holding 4096bits

- It is very impact

- CCD is volate lity storage

Question 9 Magnetic Bubble Memory?

- A thin wayer of magnetic garnet is capable of containing tinydomains or cylinders of magnetism, called bubbles.

- By erasing unwanted bubbles, the resultant presence of abubbles 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 mediumrather than a primary method of backing storage

- It is often used as a depositony for disk dumped from fixed datastorage

- 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 asmany drives are needed as reels during a processing run

- It is used as a backing medium than a primary method ofbacking storage

- The seconds usually have to be sequence where store inmagnetic tape

Chapter 7: COMPUTER FILES.

Question 1 File Processes?

d The need of sorting has dimished in line with the demise ofmagnetic tape as backing storage

b Record merging

 The records from two or more “input” files,usually in the same sequence, are combinedone record in the output file

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 certainsequence and the resultant file is in the same sequence

c Records to be summarized are generally of a similar type

Question 1 Storage and Access Modes?

There are 3 principal modes for storing and accessing accords on a disk ordrum:

1 Serial mode:

- The record are stored contigously regardless of their keys

- The sole way of accessing serial seconds is to search through thecomplete file starting with the first record

- It is sometimes possible to partition a serial files thus reducingthe search time by starting the search at the beginning of aknown partition

- A serial file is normally of a temporary nature awaiting sortinginto a useful sequence

3 Indexed_sequential/ selective_sequential mode

- Indexed_sequential is a mode of storage where by records areheld 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’skey 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 nosearching is involved

 Transaction do not need storing, thus saving time

 New records are easily insertly into the random fileprovided they are not excessive in number

 Dis

 The main problem with the random mode is inachieving a uniform spread of records over thestorage 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(oraddress)

1 Self addressing:

- Self addressing is a straight forwards method because a record’saddress 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 thestored 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 thekey required a little processing to turn it into the record’saddress

- This leads to either a pricise address

3 Matrix addressing

- In somes case, it is necessary to find the add of a record heldwithin a multi dimensional matrix of record it’s called matrixaddressing

Question 3 Direct Access Searching?

- Where as addressing determines the location of a record byusing algorithmic methods, searching finds the record byscanning groups of records, and index, or both

- ]The simplest method is to examine every record a file until therequired 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 thehighest 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 wantedkey this directs the search to the appropriate blockindex

 The block index a similarly examined and the search

 The block is searched record by record until thewanted record is found

2 Binary searching( binary chopping )

- The key in the index to be binary search must be in sequenceand form a complete set

- The search starts at the midpoint of the index and then moveshalf way to the left or right(down or up) depending upon whetherare wanted key is less than or greater than the midpoint key

- In pracice, the index is unlikely to as convenient as this examplebecause it is not always possible to exactly halve each sucessivemove(complete exact holvingis possible only when the totalnumber of keys in the index is 20-1)

- The average number of examinations comparisons is (log2k)-1 ( k

is the number of keys in the index)

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 allthe keys together with a directory showing the brachesstemming 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 keyexamination 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 thatare beyond the seach of conventionally programmed computers

2 Natural language systems (everyday native language)

- Natural language systems are programs that understand thenative language of the user, such as E

- The most popular natural language systems are those that act asinterfaces to data bases

3 Simple perception systems (for vision, speed and touch)

- They can interpret visual scenes and decide if object meetinspection 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 withupdating databases because of the difference in the type ofinformation and in the cause and effect relationship contained inknowledge bases

- A knowledge in the area, when databases may be modified by anormal 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 normallyrequires 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

- An assistant

 Is the leasts expert or lowest level ESs

 It helps a decision maker by doing routine analysisand porting out those portion of the work wherehuman expertise is required

 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 developedThere 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 testassumptions about how to encode the facts, the relationshipsand the knowledge of experts

- The prototype permits the knowledge engineer to gain theexpert’s commitment and to develop a deeper understanding ofthe 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

- The main work in this phase is the addition of a very largenumber of rules

- The knowledge base has to be expanded to full knowledge baseappropriate to the real world and the user interface has to bedeveloped

2 Phase 4 – Evaluation of the system

- This phase involves testing the system against the performanceestablised 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 otherdatabases, instruments and hardware

6 Phase 6 – Maintenance of the system

- The maintenance of the ES involves is updating, charging in thesystem when operating When operating, more problems occur inthe 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 themaintenance 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?

- 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

- 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

- To octal

100101101

 1st step change into denary = 1.28 + 1.25 + 1.23 + 1.22 + 1.20

= 256 + 32 + 8 + 4 + 1

=(301)10  2nd step: convert to octal 301 8

61 37 8

(301)10 = (455)8 (100101101)2 = (455)8 - To hexadecimal 110111011011 1st step = 1.211 + 1.210 + 1.28 + 1.27 + 1.26 + 1.24 + 1.23 + 1.21 + 1.20 = 2048+ 1024 + 256 + 158 + 64 + 16 + 8 + 2 + 1 = (3547)10 2nd 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

3 1

1 1

0 1 (247)10 = (11110111)2

= 0 1111011 x 2 normalized exponential form

Question 3 Integer and Floating – point arithmetic?

3

1 3

1 Floating – point Addition

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 performadditions, subtraction, multiplications, divisions and exponentiations

2 Input/ output instructions

They direct the computer to read data values from the specified inputdevices into the main store for processing

They also include instructions to write the contents of memory locationsholding the result of processing to a specified output device