F451 Explain

Question 1

Explain how the Program Counter is used in the functioning of the processor.

Answer 1

Stores the address of next instruction. control order of instructions executed. Number incremented after read.

Question 2

Explain why the problem must be defined accurately before the analyst starts work.

Answer 2

Client understands full potential of the system. Client expert in the problem, analyst expert in solution. Defined accurately so we know whether the problem is solvable and the right problem is solved. Final product might not match requirements (too little or too many features)

Question 3

Explain why it is important to the client and to the analyst to evaluate the finished system.

Answer 3

Determines whether analyst would be paid based on the final product produced. Make sure all the requirements have been met that the client requested. To prove that the system works as intended. Opportunity identify areas that are lacking.

Question 4

Explain how communication links are established between devices.

Answer 4

Handshake signal is sent from the one device and acknowledged by another to agree that they are ready to communicate. Logical protocols are agreed such as baud rate, parity.

Question 5

Explain why text files and streamed video may use different bit rates.

Answer 5

Video file is larger therefore sending across more data therefore sending more bits per second. Time sensitivity is factor. Streamed video is sent real time so has to be received instantaneously.

Question 6

Explain why a menu based interface is offered to visitors, rather than a GUI.

Answer 6

limited choices available limiting access to restricted parts of the program therefore finding their destination quicker. You do not need to be very computer literate to use a menu based interface/more universal. Can be touch screen therefore less vandalism. It is easy to use.

Question 7

Explain what is meant by the character set of a computer.

Answer 7

Symbols that the computer may recognise. Each symbol has a unique code. e.g. ASCII (8 bits per code), UNICODE (16 bits per code)

Question 8

By referring to two examples of applications that need character sets of different sizes, explain how codes are used to represent character sets.

Answer 8

Word processing software/Spreadsheet software. Each character has a unique binary code. The more bits in the character set the more symbols it can have. e.g. ASCII (8 bits per code) - max 256 characters, UNICODE (16 bits per code) max 512 characters

Question 9

Explain the difference between system software and applications software.

Answer 9

Applications software allows the user to perform useful tasks whereas systems software manages the hardware and provides a platform for the applications software to run on. SS has housekeeping utilities.

Question 10

Explain why a batch operating system is used to produce the payroll.

Answer 10

large amounts of data is collected inputted and stored over a long period of time. once its collected it is processed. e.g. once a week/month. No human interaction is required therefore can process at night. All similar data goes through a similar process

Question 11

Explain the need for legislation to govern the use of computers for storing personal data.

Answer 11

Information is confidential and sensitive Information must be accurate Clients must have confidence that measures are taken to protect
their data (Data stored must be refreshed regularly to) ensure irrelevant data is not kept Worry about identity theft/fraud.Stop data being passed on

Question 12

Explain the changes to the staff’s work expectations following the introduction of the computerised system.

Answer 12

(Worry about) job loss (Worry about) competence/training
More information available/available when needed Change of stress levels More chances of improved qualifications/training makes workers
more skilled enhanced job prospects/more pay Expected to be more literate with system Increased work load to bring new system on line

Question 13

Explain why a handshake signal is necessary.

Answer 13

To ensure that both devices are ready for data transmission. To ensure that same protocol are being used. e.g. agree error detection rules

Question 14

Explain the difference between the hardware and the software of a computer system.

Answer 14

Hardware is physical parts of system Software is instructions/code/programs

Question 15

Explain the importance of accurately defining the problem to be solved and state what each
of the analyst and the manager are able to contribute to the problem definition.

Answer 15

The two people involved will have very different ideas of the problem /
Necessary that they solve problem which they agree on… …or manager will be unhappy/software will be useless… …analyst will not be paid.Analyst is expert in use of computers Manager is expert in area of problem

Question 16

Explain how echoes can be used to check data transmissions.

Answer 16

Data is transmitted from sending device to receiving device. A copy of received data is retransmitted back to sending device. There the data transmitted is compared to what was originally sent. If any differences the data is retransmitted from sending device.

Question 17

Explain why custom-written software is often used rather than generic applications software.

Answer 17

Process is a unique/a one off
Generic software will not exist (to just do this)
The generic control software will have many unused features/bespoke written specifically for this purpose
Custom written software can be written to allow ease of changes to production

Question 18

Explain why the quality of the interface design is important in applications.

Answer 18

Critical nature of application.
Large amount of information…
…only one operator.
…operator may miss seeing some important piece of information
…information must be ordered in terms of importance r according to a logical pattern.
…danger of information overload
Remove irrelevant information
…need for information presentation to be prioritised according to importance
some information is crucial eg possible conflict between signal and points arrangement
Use of colour must be consistent.
Consistency of presentation
Use of sound must be minimal otherwise it will be ignored
Must consider operator eg is the operator colour blind/deaf

Question 19

Explain why the protocol used to create an interface between two devices is layered.

Answer 19

Enables manufacturers to design for a particular layer
Layers are ordered…
…which simplifies the creation of the protocol
Changes can be made by altering a single layer…
and the links to the other layers in contact with it

Question 20

Explain why verification is not required when data is read automatically into a computer.

Answer 20

Verification checks for errors created by copying data from the original document into the computer manually
Data has no been transcribed/no human involved in input…
…so there is no possibility of a transcription error/no room to introduce error to the data

Question 21

Explain the double entry method of data verification for data entered manually.

Answer 21

Verification checks for errors creating by copying data from the original document into the computer manually.
data is manually inputted twice. The computer compares the two sets of data that have been entered. When there is a difference between the two sets of data the user is asked to reenter the data.

Question 22

Explain what information would be stored in order for the payroll system to work.

Answer 22

Nation information about individuals eg NI number/tax code
Personal information eg address, phone number/payroll number
Financial information eg Bank account number/previous earnings
Holiday dates/grade of pay
Health issues

Question 23

Explain one method of checking data to ensure that it has been transmitted without corruption

Answer 23

Block of data is sent and received, received block is then returned to transmitting device where it is compared to the block that was originally sent. if there is a difference the entire block is re-sent. This is an echo error check.

Question 24

Explain the analysis stage of the systems life cycle including any diagrams that the analyst will be expected to use during the analysis.

Answer 24

Feasibility study will be carried out, outputs and inputs required will be found. forms that inputs/outputs take. types of data that are held. form in which data is held.

Question 25

Explain the main difference between a multi-user operating system and a network system.

Answer 25

A multi user system allows a number of users to use one computer at the same time. a network. a network system allows a number of computers to share other resources at the same time.

Question 26

Explain what is meant by data validation.

Answer 26

The comparison of the input data with rules that the data must follow. validation carried out by the computer/system, not the user. checks data for being sensible, not for being correct.

Question 27

Explain three differences between circuit switching and packet switching when transmitting data on a network.

Answer 27

PS has no established route/CS establishes a route for duration of message
PS means packets being sent on individual routes/CS sends packets all on same route
PS message cannot be intercepted/CS message can because all on same route
PS packets (arrive out of order and) must be reordered/CS packets remain in correct order/must be reassembled
PS maximises use of network/CS ties up large areas of network

Question 28

Explain how the binary value of a number can be used to produce the octal value.

Answer 28

Take the binary value of number. group them into groups of 3 from right to left. Take the decimal value of each if the groups. e.g. 10110101, 101 = 5, 110 = 6, 10 = 2 so 10110101 in octal is 265.

Question 29

Explain how a check sum is used to check transmitted data for errors.

Answer 29

Blocks of bytes are added before transmission. To give a total, with ‘carries out of the total’ ignored. This total is transmitted with the block. The same calculation is done on the data blocks at the destination. The result is compared with the transmitted value, if different, there is a transmission error.

Question 30

Explain how parity checks of data blocks can sometimes be used to correct transmission errors automatically.

Answer 30

Each byte and bit have a parity bit. All parity is checked. If there is an error in the parity for a byte and the parity for a place value, then where they intersect will be a faulty bit. If it’s 0 change it to 1 and vice versa. If there is more than 1 error in the block, data is re-transmitted.

Question 31

Explain why the control software is stored on ROM.

Answer 31

Will not need to be changed
Cannot be changed
Will not need loading/installing
Immediately available when switched on

Question 32

Explain why it is necessary to have some RAM.

Answer 32

Need to allow user to enter data
Processor must have some RAM as working memory/buffer
Used to load data from disk when playing/currently running programs/data in use

Question 33

Explain why a systems analyst needs to identify the information requirements of a system.

Answer 33

Need to ensure analyst understands the organisation requirements…
or system produced may not meet requirements
Need to ensure correct hardware and software
Interview/one to one situation/can change course of questions/Boss or client
Questionnaire/many have their views considered/time saving/large workforce
Observation/can see process in action/may not act as they would because being observed
Meeting/can get views from many people at once/may be taken over by one or two people
Document collection/indicates what data is actually collected.

Question 34

Explain why optical mark reading (OMR) is a sensible way of marking candidates’ papers.

Answer 34

Optical Mark Reader/Recognition Positions of marks on a document… Equate with information Document is scanned for coordinates of marks

Question 35

Explain the use of code to represent a character set.

Answer 35

The characters that are recognised by the computer Each character is represented by a unique binary number Often matches the characters available on a keyboard/accept
reasonable description of data

Question 36

Explain the need for firms to back up and archive the customer data and the procedures for carrying out these processes.

Answer 36

Need for back up and archive:
Back up necessary in case of corruption of data…
…either maliciously or accidentally
If data destroyed then firm will have to shut
Archive necessary to keep copy of data for future use
Frees up space for new material…
…by removing little used or redundant data
Used by firm for mail shots, the following year
Procedure for back up:
Length of time between back ups/daily
Mention of medium used/DVDRW

Question 37

Explain why some customers may be concerned about giving their personal details to a company.

Answer 37

Information can be looked at by others
Information may be hacked/worries about privacy
Data can be used to commit fraud/steal from accounts Worries created by reports in the press
Information may be sold on/passed on
Information used to send junk mail
Customer does not know what use may be made of the data

Question 38

Explain the importance of evaluating the system and the criteria that should be used in the evaluation.

Answer 38

(Client must evaluate system to) ensure that the requirements have been met
Analyst must evaluate system to provide evidence that they should be paid -the criteria should be the agreed set of objectives of the system
This will be done by the rigorous testing of the system…
including normal and abnormal data…/functional testing
and using the end user as a tester/acceptance testing

Question 39

Explain how the student can use file handling utilities with the computer.

Answer 39

Copying of files from one medium/place to another/to take into school/make backups
Deletion of files from storage when coursework handed in/more recent version stored
Security measures/access management
Storage of files on secondary storage…
use of folders/directories/different file extensions
Opening files/folders to retrieve data when required/use of shortcuts created on desktop

Question 40

Explain why it is important to define the problem accurately.

Answer 40

The analyst and client will have different ideas of the problem so it is necessary to agree on what the problem is to prevent the wrong solution being made. If that happens, the client will not be satisfied since the software does not solve the problem and the analyst will not get paid.

Question 41

Explain how a knowledge-based system would be used.

Answer 41

Data about a certain topic is collected and inputted into the system. The user then asks questions using the prompts from the system. The system would then give answers based on the queries.

Question 42

Explain, giving examples, the relationship between bit rates and the time sensitivity of the information being communicated

Answer 42

Some data is not used immediately, and is downloaded onto storage so it does not need to be transmitted at a fast rate. It is not time sensitive because it is saved. E.g. A picture. However some data must be used real time, and is time sensitive because if it is not used immediately it will lose its value. E.g. Streaming a video

Question 43

Explain the difference between a batch operating system and a real-time operating system.

Answer 43

In a batch operating system, the data is collected first and the processed all together while as in a real time operating system, data is processed immediately.

Question 44

Explain what is meant by an archive of a file and why it is necessary.

Answer 44

Contains data no longer in use in case it is needed again. Frees up space on the storage of the system. Stored in a secure location/away from the computer system

Question 45

Explain how the measures of the Data Protection Act are designed to protect the privacy of data.

Answer 45

Customer has the right to see the data and to ask for it to be corrected if wrong so that they are not responsible for incorrect data.
data must be lawfully collected so that Customer rights are not flouted.
data can only be accessed by/changed by authorised people so that malicious alterations are not made.
data is only used for the specified purpose so that junk mail is not encouraged.
data should be accurate and up to date so that customers are not held responsible for goods they have not bought

Question 46

Explain why sign and magnitude form is rarely used for computer arithmetic.

Answer 46

Because there are 2 types of data in the same binary value which must be treated differently so it makes arithmetic algorithms complex

Question 47

Explain the design stage of the systems life cycle, including the use of prototyping, that the analyst will be expected to use during the design.

Answer 47

Design of input screens/methods of input Design of the output screens/hard copy outputs/other forms of output
Design of the data structures to be used to hold data
Design of the processing required to change the input data into acceptable output.
Data flow diagram/to show how data moves through the system.
including where it will come from, what processing is carried out and where results will go.
Data required is dependent on outputs required which in turn dictates the required input to the system.
The processing required dictates the type of storage to be used and the data structures required.
The form of the output will dictate the peripheral devices that are uses

Question 48

Explain the role of the printer buffer in the transfer of a job from the computer to the printer.

Answer 48

Buffer is filled by the computer with job which needs to be done.
Printer then downloads contents of Buffer and carries out printing.
This is necessary to allow the computer to continue with other work while the Printer is occupied.

Question 49

Explain why an interrupt is necessary during the transfer of data from the computer to the printer.

Answer 49

Operating system needs to know when the Buffer has been emptied/filled so it can be refilled.
The interrupt is sent from the Buffer/accept Printer to the computer.
The interrupt is sent from the Buffer/Printer to the computer requesting more data to be transferred.