Computers & ICT: Post your doubts here!

[Tkp]

Which variant, bro???

1

 

[AAnsarii]

Student of the year Tkp syed1995 ahifan

 

[Student of the year]

Student of the year Tkp syed1995 ahifan

Thats very nice & helpful......Jazakillah dear.....

 

[Student of the year]

1

w11_qp11_q5a

recording of info will help in:
establishing the inputs ,outputs & processing of the existing system.
identify problems with current system: the info will be used to see whether there is data duplication or weakness,etc.
identify hardware & software (for new system):know the volume of data to be used; the size & speed of processor required; no of storage devices; etc.
identify (user)requirements:see what each worker doing, & what they need in future.
produce requirements specification:list of features required-general & specific.


see the section 4.1 of the book.
it simply outlines the aspects of analysis stage alongwith recording of info,
so the other titles than recording info is the ans of this question.

Hope it helps you.....

 

[Dug]

Computing 9691 P1

No credits to me. I only compiled!! Most of this is copy-paste but I hope it helps!

========================================
- serial storage e.g Transaction log (a seperate file of all the changes that have been made since the last backup)

-bootstrap stored in ROM >>> other e.g (fonts within laser printers), (the 'character pattern' memory in cmd)
-User software and data stored in RAM >>> other e.g (parts of the OS in use)

-Network Basics:
>> Computers need to communicate so there is a need of special hardware attached to the processor, called a Network Card.
>> Cable to carry signals from one point to another on the network.
>> A network server is needed to control access to peripheral devices and to files on the shared hard drive.
>> To control the communications, a set of instructions that the network will follow is required. This is called Network software or Network OS.

** WAN uses telephone system to connect the computers.

-Difference b/w LAN and WAN:
>>LANs are networks covering a single site, while WANs are networks connecting geographically remote nodes
>>LAN uses its own communication medium while WAN uses third party
>>LAN more secure while WAN more open to attack


- Checksum is used for large blocks of data (e.g internet packets which use 32-bits checksum) while parity is used on smaller blocks of data.

-Protocols for devices like Computer and Printer:
1)Baud rate >> necessary because if the computer transmits at a different speed to that which the printer can recieve, the message will become jumbled.
2)Parity type >> because if the computer transmits using odd parity and the printer checks using even parity, correct bytes will never be accepted.


============================================

 

[Dug]

Defs

-Hardware: The physical parts of a computer system
-Software: Set of instructions which tell the computer how to perform a certain task

-Generic software: Software which is appropriate to many applications within a skill area.
-Application software: A set of instructions which make the computer do something useful.

Operating system: A (suite of) programs which run the basic functions of the computer/controls the hardware giving an environment in which to run application software.

-Distributed system: A distributed system is one which uses many storage locations on different machines to store software and files.
*adv*
Access to files can be speeded up because more than one file command can be carried out at a time.

-Algorithm: A sequence of step by step instructions for solving a problem
-Flowchart: A graph consisting of geometrical shapes that are connected by flow lines.It is another technique used to represent algorithms.

-Field: Storage space for one data item.
-Record: The data structure which contains all the information about an instance of an entity.
-Fixed length record: A record where each field is defined with a specific length.
-Variable length record: A record where at least one of its field has variable length.
-File: The data structure which contains the data of all the instances of an entity.


-Buffer: An area of fast access storage between two components/devices into which data is temporarily stored during data transfers between components/devices that operate at different speeds.

-Interrupt: A signal from the component/device to the processor, to indicate that it needs attention.

-Peripheral device: Any hardware device that is part of the computer system but is not part of the processor itself, is called a peripheral device.
Types: Communication devices, Storage devices, Input devices, Output devices

-LAN: the computers on the network are close to each other.
-WAN: the computers on the network are remote from each other.

-Serial transmission: Where data is sent only one bit at a time along a single wire. (e.g wires in a network)
-Parallel transmission: Where multiple bits are sent simultaneously. (Fast but not reliable as the bits can become muddled up - out of sync) (e.g internal components of a Computer)


-Simplex: Data can be transferred in one direction only. (e.g transmission of a television picture from transmitter to the recieving aerial)
-Duplex: Data can be transferred in both directions at the same time. (e.g a telephone conversation)
-Half-Duplex: Data can be transferred in both directions, but only one direction at a time. (e.g a walkie talkie where the handset needs to be set to either send or recieve mode)

-Network Card: A small electronic circuit board within a computer that controls the sending and recieving of data in a LAN. (e.g internal components of a computer use parallel bits and the network card translates the parallel signals to serial signals so they can be carried down the wire.)

-Bit-rate: The number of bits transferred in each second. (unit is BAUD= 1 bit per sec)

 

[Dug]

-Error checking and correcting
>> Echoes: A method of error-checking whereby the data that is recieved is sent back to the sender to check that it is unchanged. (very effective but have to send data twice taking longer than necessary and needs a duplex or half duplex system)

>>Parity: A parity bit, or check bit, is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd.

>>Checksum: A check sum is a value which is computed from a block of data and is transmitted or stored with the data in order to detect a change.

-Packet Switching: Where the message is split into a number of equal-sized packets. Each packet is labeled with the destination address and the packet number. Packet switching does not need a route to be established before transmission (packets are sent independent of each other through different routes). At each node, the label is checked and the packet is redirected. At destination the packets are rearranged according to their packet numbers.
*adv*Allows optimum use of the connections around the network because as many routes are in use at one time as possible.

-Circuit Switching: Where two computers that want to exchange data establish a path through a network, which is then used for the entire transmission.
*adv*The whole message is kept together so it does not have to be reassembled at destination + Very little processing required overhead
*disadv*When the connected devices do not transfer data continuously.The connection is idle and bandwith is wasted + Cannot connect computers or devices that operate at different transfer rates.

-Protocols: The set of rules that needs to be set up to allow the transfer of data to be carried out is known as a protocol.

-OSI model: The OSI (Open Systems Interconnection) model is a model that describes what happens to some information when it is being sent from one computer across a network to another.
**Information moves from one PC, through the 7 layers, across a network, up through the 7 layers again to another PC.
-layering: taking all of the protocols and standards and grouping them into one of the seven layers.

-Jackson structure diagram: The solution is gradually divided into modules which are more manageable. Jackson structure diagram is the representation of these modules in a hierarchical diagram.

-Data flow diagram: A drawing that depicts the transformation of data within an existing system by using three different graphical symbols connected by labelled, diected lines.

-Stock control: An application used to keep track of the stock being held by the organisation.

-Transaction log: A separate file of all the changes that have been made since the last back up.

-Data logging: When data is collected off line, often by sensors in remote locations, and then stored until ready for input to the system at a time that is convenient to the system.

-Data validation: Method of checking whether the data inputted to the system is reasonable and accurate.

Presence Check : Checks that data has been entered into a field and that it has not been left blank. e.g. check that a surname is always entered into each record in a database of addresses.
Type Check : Checks that an entered value is of a particular type. e.g. check that age is numeric.
Length Check : Checks that an entered value e.g. surname is no longer than a particular number of characters.
Range Check : Checks that an entered value falls within a particular range. For example the age of a person should be in the range 0 to 130 years.
Format Check : Checks that an entered value has a particular format. e.g. a new-style car registration number should consist of a letter followed by 1 to 3 numbers followed by 3 letters.
Check Digit : A check digit is a digit attached to the end of a string of digits. It is calculated from the other digits and used to help ensure that the whole string is inputted correctly.
Parity Check : Used in data communications to ensure that data is not corrupted when it is sent down a transmission medium such as a telephone line.


-Verification: Checking the input data with the original data to make sure there have been no transcription errors.

-Expert system: An expert system is one which contains as much data as possible about a restricted knowledge area. (e.g oil exploration system)
*4 parts* -Knowledge Base, -Rule base, -Interference engine, -HCI

-Timeliness: This is the concept that the data changes over time and that data is only a part of a sensible
solution for a short period of time before it becomes outdated.

-Relevance of data: This means that the data has a bearing or use, in a particular application.
============================================================


9. A school computer department has decided to invest in new hardware in the two
rooms that it uses for computer lessons in the school.
The teacher in charge has to decide between a network of computers or a collection
of stand alone machines. The teacher has asked your advice about which hardware
solution to implement.
a) State four advantages in implementing the network solution. (4)
b) State a disadvantage of using a network in this context and suggest a solution to the
problem. (2)
A.a)-Hardware can be shared. There is no need for a printer for each machine.
-Software can be shared. Only one copy of each piece of software is required.

-Pupils can access their files from any machine on the network, they do not have to
use a particular machine.
-Communication can be carried out between machines in the two rooms.
-Files stored on the disk drive only need to be updated once, so all machines can
access the same information in common files.
b) -Files are less secure because of reliance on single drive
-regular back up copies of files should be taken.
-Privacy of files is more difficult to control because of common access to hardware
-Use of passwords to control access to files.

=========================================================

-Is the solution technically possible?
-If the hardware or software does not exist then the solution cannot be implemented

-Is the solution economic to produce?
-If the cost of the new system will not reasonably be recoverable then it is not sensible to produce it

-Is the solution economic to run?
-If the running costs will not be smaller than at present then cost is not a reason for change

-Effect on the work force
-If the human cost (e.g. mass redundancy) is great then there may be unacceptable social costs

-Is the work force skilled enough?
-If there are no skilled workers to work the new system then it is not worth producing

-Will customers notice a difference?
-If there is no improvement in price/quality/reliability of the product then is the extra expense worthwhile?

-How long will the introduction of new system take?
-If it is too long then any beneficial effects may have been lost

-What are the legal implications?
-e.g. if the DPA says that it is not legal to use the data in this way then the proposed system cannot be used

 

[Dug]

=============================================================

Questionnaires:
*adv*
-Large number of people can be asked quickly
-All employees percieve that they have had a say
-Maintain anonymity
*disadv*
-Restricted responses possible
-Some may have difficulty completing them
-Few replies

Interviews:
*adv*
-Comments can be at length
-Extension questions can be asked as a result of user's answers to original questions
-Can squeeze out confidential information from employees
-Can leave a prepared script
*disadv*
-Lengthy
-Limits the number of views that can be sought
-Generalised answers

Group discussions:
*adv*
-Many people can air their opinions
-Cuts down the number of repeat views obtained in interviews

*disadv*
-Some people may hog the discussion
-Some people's views may not be heard

Observation of the work environment
*adv*
-Shows present system, not just views which may be clouded
*disadv*
-People tend not to act in the way they normally do
-Data and forms tend to be seen in isolation

Inspecting documents
*adv*
-Obtaining the format of input and output
*disadv*
-Volume collected
-Data and forms tend to be seen in isolation

===================================================

System changeover

Parallel running: (e.g exam marks processing system)
The old and new systems are run side by side until it is made sure that the new system is fault free.
*adV*
-The results of the two systems can be compared to ensure that there is no fault with the new system.
-The staff training on the new system can be carried out effectively.
-Always have a fall-back system in case of a system failure

*disadv*
-Very expensive and time-consuming
-Creates confusion among the staff
Pilot running:
The new system is implemented initially only in a certain part of the company such as a branch.
*adv*
-If there is a fault in the new system, it would affect the organization only in a relatively small area of data processing.
-It allows the analyst to test how the system would perform with a smaller amount of data.
-The staff who were part of the pilot scheme can help train other staff.

*disadv*
-If a part of the new system fails, there is no back-up system, so data can be lost.
-Its not possible to check how the system would perform with a large amount of data.

Phased implementation:
The system is implemented by replacing the parts of the old system gradually with the corresponding parts of the new system while the rest of the system is still running with the old system.
*adv*
-Can repair a faulty module without affecting other modules.
-It allows staff to be trained gradually

*disadv*
-The old and new parts may not be compatible.
-Takes relatively long time to implement the new solution.

Direct changeover:
The new system replaces the old system immediately and completely.If the new system does not work then the admin must shut down
*adv*
-Minimum cost and effort
-No confusion to the staff

*disadv*
-If the new system fails, there is no back-up system, so data can be lost.
-Allows no time for training and finding errors.

==========================================================

What is point of sale (POS)?
Point of sale is a terminal connected to a main computer.
The input devices used at a point of sale are:
1. Barcode reader – scans the barcode fixed to an item by recognizing the thickness of the bars
to
allow the interpretation of the item number.
2. Keyboard – allows the operator to input barcode, price and other details manually in case the
barcode reader cannot read the barcode.
3. Swipe card reader or the smart card reader
Allows reading data from a credit/debit/bank card or to send those details to the bank
4. Scales
To measure the weight of an item
5. Customer keypad
For the customer to input the PIN

The output devices used at a point of sale are:
1. Printer
To print the till receipt
2. LCD
To show purchase details and the cost of item
3. Buzzer
To confirm the reading of the barcode

************************************************

Design involves:

- Diagrams used to plan new solution/DFDs/Algorithms
– Designs of Input and Output screens / user interface...
– probably as prototypes with nothing behind them
– discussion between analyst + client/user
– hardware/software requirement considered
– Data structures will be designed
– Processing requirements will be decided
– Objectives agreed with client
– Design test strategy

Implementation involves:
– Purchase and installation of hardware
– Installation of software on the hardware
– Creation of data files
– Producing user manuals
– Consideration of need for training staff
– Method of changeover decided
– convert/transfer files
– Consideration of future maintenance of system
– Uninstalling the old system
– Monitoring initial performance of system

 

[Dug]

Computing 9691 P2

-----------------------------------------------

Dim VariableName As DataType 'for variables
Dim ArrayName(Size) As DataType 'for array
----------------------------------------------


---------------------------------------------------
Initialising:
Dim Array(10) As Integer
For i=1 to 10
Array(i) = 0
Next
--------------------------------------------------

----------------------------------------------------------------------------------------------
Public/Private Function FunctionName (Var1 As datatype1,Var2 As datatype2,...) As Datatype 'User-defined function
--------------------------------------------------------------------------------------------------

-----------------------------------------------------------
Public Type EmployeeRecord 'User-defined types
strEmpName As String
dtmHireDate As Date
sngHourlyRate As Single
End Type

Dim udtEmpRec As EmployeeRecord
udtEmpRec.strEmpName = "JOE SMITH"
udtEmpRec.dtmHireDate = #1/15/2001#
udtEmpRec.sngHrlyRate = 25.50
-----------------------------------------------------------------

 

[Dug]

-------------------------------------------------------------------------------
Describe how an array is initialised in the memory of a computer.

-Size of array calculated
--Location of array decided...
-according to data type/size
--Locations reserved
--Array named in the look up table
--Size of array stored in table
--Lower bound of array stored in table
-Upper bound of array stored in table
-Data type stored in table
--Adress of first element stored in table

Describe how an array may be searched serially to find a specific data item.
-Index set to 0
-Array(index) searched
--If = item then 'found'
--Else increment index and repeat
--Until found or error report

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@


Debugging Methods:

Cross Referencing (Checks Program for Duplicate Variables Used)
Tracing (Step-By-Step Checking Each Instruction until Errors are Found)
Variable Dumps (All values of Variables used are displayed to enable the User to compare them with the Expected Results)
Desk Checking (Dry Run which Programmer Tests Code for Errors Manually)

Testing Methods:

White Box Testing (Testing Code, All Paths) - Testing all possible routes through the program logic/ Testing knowing the code
Black Box (Testing All Outputs) - expected results compared with actual results/ Testing not knowing the code
Alpha Beta Testing (Alpha: People in Company Testing Code, Beta: Ordinary Users Testing The Actual Program)
Alpha Testing - Testing by programmer
Beta Testing - Testing by public/end-users/potential users

Loops:

FOR...NEXT
WHILE...ENDWHILE
REPEAT...UNTIL
DO...UNTIL

Errors:

Syntax Error - a statement does not follow the rules of a programming language e.g PLINT instead of PRINT
Arithmetic Error - inappropriate arithmetic is used e.g division by 0 is attempted
Overflow (Runtime) Error - an error that can only be detected while the program is being executed (can't be detected during compilation)
Logical Error - an error in the design of the code /OR/ a mistake in the structure of the code e.g a jump goes to the wrong line
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

1. How to initialize an array:
Dim Array(10) As Integer
For i = 1 to 10
Array(i) = 0
Next i

2. Declaration of variables:
Dim VariableName As DataType

3. Using loops:
While CONDITION 'Checks Condition at the Beginning
...
EndWhile

REPEAT
...
UNTIL Condition 'Check Condition at the End and does the code at least once

4. Structures:
STRUCTURE StructureName
DIM Var1 AS DataType
...
DIM VarX AS DataType
END STRUCTURE

4. Procedures & Functions:
PROCEDURE Name
Instructions
END PROCEDURE

FUNCTION Name
Instructions
END FUNCTION

6. Pseudocode
Write in simple and Understandable words like a story of events.

READ FILE
UNTIL NOT EOF, DO
INSTRUCTIONS
LOOP

*EOF = End Of File

 

[Dug]

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Input n
a=1
For i=1 to n
a=a*n
Next i
Output a
End

or

Function Factorial
IF n=1 THEN
Return 1
ELSE
Return n*Factorial(n-1)
END IF

-----------------------------------------------

Serial search on an array
The following pseudo-code can be used to search an array to see if an item X exists:

01 DIM Index As Integer
02 DIM Flag As Boolean
03 Index = 0
04 Flag = False
05 Input X
06 REPEAT
07 IF TheArray(Index) = X THEN
08 Output Index
09 Flag = True
10 END IF
11 Index = Index + 1
12 UNTIL Flag = True OR Index > Maximum Size Of TheArray

-----------------------------------------------------
Adding data
Serial file

Adding data is simple – it is added to the end of the file:

OPEN File in WRITE MODE
GOTO End of File
WRITE NewData
CLOSE File

--------------------------------------------------------

Sequential file

OPEN a NewFile in WRITE MODE
OPEN ExistingFile in READ MODE
READ First Record in ExistingFile
REPEAT
IF key of SelectedRecord in ExistingFile < key of NewRecord THEN
COPY SelectedRecord into NewFile
ELSE
COPY NewRecord into NewFile
COPY SelectedRecord into new file
END IF
READ Next Record in ExistingFile
END REPEAT when new record has been copied
COPY ALL remaining records from ExistingFile into NewFile
CLOSE NewFile and ExistingFile

----------------------------------------------------------

Random file

OPEN File in WRITE MODE
READ KeyField of NewRecord
Apply Hashing Algorithm to calculate DiskAddress
WRITE NewRecord to calculated DiskAddress
CLOSE File

THE HASHING ALGORITHM:

[DISK ADDRESS] = PrimaryKEY MOD NumberOfBlocks + [StartAddress]

----------------------------------------------------------

Searching for/retrieving data

Serial file

OPEN File in READ MODE
READ First Record
SET Variable Found = False
REPEAT
IF RequiredRecord = SelectedRecord THEN
SET Variable Found = True
ELSE
READ Next Record
END IF
END REPEAT when Found = True OR when EOF is reached
CLOSE File

-----------------------------------------------------------

Sequential file

OPEN File in READ MODE
READ First Record
SET Variables Found = False, Exists = True
REPEAT
IF RequiredRecord = SelectedRecord THEN
SET Variable Found = True
ELSE
READ Next Record
IF Key of RequiredRecord > Key of SelectedRecord THEN
Exists = False
END IF
END IF
END REPEAT when Found = True OR Exists = False OR when EOF is reached
CLOSE File

---------------------------------------------------------

Random file

OPEN File in READ MODE
READ KeyField of RequiredRecord
Apply Hashing Algorithm to calculate DiskAddress
READ Record at DiskAddress
IF Record does not exist THEN
OUTPUT “Record Not Found”
END IF
CLOSE File

---------------------------------------------------------------

 

[Esme]

Dug may I ask what all these notes are for?

 

[syed1995]

Dug

Chah gaye sir jee! Awesome stuff.. I didn't knew you had computing as well..!

 

[Dug]

Dug may I ask what all these notes are for?

A level Computing (9691)

 

[Esme]

A level Computing (9691)

Oh ok. I got confused cuz I have Applied ICT.

 

[Student of the year]

=============================================================

Questionnaires:


Interviews:
*

Group discussions:
*

Observation of the work environment


Inspecting documents


===================================================

System changeover

.

Phased implementation:

Direct changeover:


==========================================================


************************************************

Design involves:

-
Implementation involves:
–

I`m not a computing student bit this ones helpful for me too........
so JazakAllah bro..
& May Allah reward you for this help of yours to others.....Ameen.

 

[Tkp]

A level Computing (9691)

well i must appreciate you for the hard work.may God give u good grades in ur exm

 

[Esme]

ICT isn't my strongest subject so bear with me if this question is very childish
Is intranet the same as LAN?
And is WAN/Internet the same as extranet?
If not, please tell me how they're different

 

[iFuz]

I need answers to following questions:

• How memory is classified on basis of speed?
• Differences b/w main and secondary memory?
• Difference b/w SRAM and DRAM?
• Define Cache and its use? [3]
• Whats PROM?
• Whats EPROM?
• Whats EEPROM?
• How data is removed from EEPROM?
• What is data-rate?
• What is seek time?
• One nibble = ____ ?
• What is access time?
• What is transfer delay?
• Explain Two's compliment?
• What is drum plotter?
• Where electrostatic printer is used?
• How data is stored and retrieved from a hard disk?
• What is Flash Memory? Explain its importance?
• Differences between DIRECT ACCESS MEMORY, SEQUENTIAL ACCESS MEMORY ?
• What is Auxiliary Storage?

 

[syed1995]

Reviving the thread.. Computing P1 coming up!