AS Computing

The Internet

a publicly accessible international collection of interconnected networks, gateways, servers and computers using a common set of telecoms protocols to link them together. Information on the internet is Instantly available to a potential audience of hundreds of millions.

Connecting to the Internet

when you connect to the Internet, you do not connect directly to the Internet backbone, you connect to an ISP which connects to the backbone.

WWW

Generic name given to all hypertext-based HTML documents on the Internet.

Intranet

A collection of web pages held locally on the server of an organisation. These typically contain information that should not be made publicly accessible, as INTRANETS are only available to members of an organisation who have authorisation to access them and the necessary login details.

Advantages for businesses

Internal job adverts

Internal telephone and e-mail directories

Various forms used for admin purposes

Staff holiday dates

Forthcoming events for staff such as Christmas party

Internal communications

Extranet

Available to people who are not members of the organisation, such as customers. Access is allowed upon password verification and from anywhere in the world.

Advantages

Exchange large volumes of data

Share product catalogues exclusively with trade partners

Collaborate with other companies on joint development efforts

Jointly develop and use training programs with other companies

Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks

Disadvantages

Doin a practice paper

1 a) Using electronic mail will save on resources such as paper. Letters can be personalised quickly and easily using the athletes’ personal details (name, etc) through mail merge and templates. However, emails may end up in the users’ spam or trash can, causing the customers to miss out on potentially valuable marketing information. 2 Email arrives same day/quicker than traditional letters

b) Data must be lawfully obtained and processed in accordance with the data subject’s rights

Data must not be processed outside of the EU without protection of the user’s freedoms/rights

Data must not be adequately relevant and not excessive

Job 1: Managing Resources

Manages peripherals such as input and output devices and communicates with and sends data output to a printer, monitor, keyboard, etc

Memory Protection

Each program is given an area of memory to use. If a program attempts to use another’s memory, a Memory Protection error is displayed and the program is halted.

Time Slice:

Time slicing allows the users/applications to share the processor. The processor allows a finite amount of time or a time slice for each process (job) that it has to execute. At the end of the time period, the processor moves on to the next job and so on. The method allows many applications to be run seemingly at the same time.

Spooling:

Data is stored on a hard disc/in memory/in a queue

Document is printed when printer is free/in correct order

User can carry on working/log off while waiting for the job to print

Job 2: Managing Backing Store

Ensures that data is stored and can be retrieved correctly from the hard disc drive or other storage devices such as CD ROM drive / DVD drive and communicates with and sends data output to a printer, monitor, keyboard, etc

Hierarchical Structure:

The OS is responsible for making sure files are stored in a hierarchical structure. The top level of the hierarchy is called the root directory.

Related files can be stored together

Files are easier and quicker to locate

Can easily identify the path to file

Files can have the same name if stored in different directories

Job 3: Memory Management

Manages memory (RAM) by allocating the right amount of space for the programs when they are loaded so they do not get corrupted

GUI:

The most common type of GUI is WIMP

Advantages:

Instinctive to use

No need to learn a set of commands to use the interface

Disadvantages

Uses a lot of processing power

Runs relatively slower than command line interfaces

Command Line:

This type of interface requires typed input from the user which the system executes to produce the desired output. The user must be proficient in the commands for the interface to be used efficiently. This type of interface is mainly suitable for experienced users who are familiar with the commands. MS DOS 6.0 is an example of a command line interface.

Advantages

Can be installed and used on low spec machines

Very quick to execute commands

Disadvantages

Need to learn the commands before using the interface

Other

Manages virtual memory by swapping files between the hard disc and RAM using Page Files

Manages processes by allocating a time slot for each process (time slicing)

OCR: Optical Character Recognition

Recognises the pattern of dots as a letter and stores the ASCII code in the file being created.

For example, the dots are recognised as the letter A, which is the ASCII code 65, which is then stored in the file being created.

Step 1: SCAN the document

Step 2: RUN the OCR software

Step 3: EDIT using a WORD PROCESSOR

Applications of OCR

Scanning books to make them available online/digitally

Scanning a questionnaire for data analysis

Other forms of input

Applications of Voice Input

Dictation systems

Giving commands to the computer

A voice enabled SECURITY system

Issuing commands to a mobile phone

Applications of Handwriting Recognition

Mobile phones and PDAs

Tablet PCs such as iPads

Applications of Biometrics

SECURITY ENTRY systems to prevent unauthorised access

To verify/validate traveller identity at air ports

Advantages

Fingerprints are unique to a person

Passwords can be guessed but fingerprints are hard to copy

Passwords can be forgotten

Passwords need added security eg being changed regularly

Disadvantages

For people affected with illnesses such as diabetes the eyes get affected resulting in problems when using biometric scanners

Bit: Binary Digit: the smallest unit of storage in a computer - can hold either a 0 or a 1.

8 bits are required to store a character.

Byte: 8 bits

World Length

A word is the size of data that can be fetched from memory and processed by a processor in one go

More powerful processors may use 16 or 32 bits words. In a 32 bit computer, the data bus and registers will all be 32 bits.

A computer with a word length of 32 bits will process data twice as fast as one with 16 bits.

Address Bus

The number of wires in an address bus shows the number of locations in RAM.

(3 wires = 8 locations. 2^3 = 8.)

Unidirectional (CPU to RAM)

Data Bus

Each bit of data has its own wire; number of wires determines the size of the location

Each memory location is 1 byte

Bidirectional

Control Bus

The Central Processing Unit (CPU)

ALU: Arithmetic and Logic Unit

does the arithmetic calculations and places the result in the accumulator

MAR: Memory Address Register

sorts out all the internal paths needed inside the microprocessor to make sure that details fetched from the right place are taken to the right place

instructs the ALU which logical operations to be performed

controls the Fetch-Decode-Execute sequence

PCR: Program Counter Register

holds the address of the next piece of data/instruction that needs to be fetched from the main memory

when the address of the current instruction has been dealt with, the program counter is incremented by 1, so the processor is ready to fetch the next instruction

CU: Control Unit

IR: Instruction Register

the binary digits of the most recently fetched instruction are held here so that the instruction decoder in the Control Unit can decode them

MDR: Memory Data Register

holds the address of the instruction (or data) currently being accessed

Address Bus

Data Bus

Main Memory

ROM and RAM

Contains programs and data currently in use.

How programs are executed by the CPU

The Fetch Execute Cycle

1: Fetch

2: Decode

3: Execute (and back to 1)

Stored Program Concept (aka Von Neumann architecture): a computer with this stores program data and instruction data in the same memory

Register

A special high-speed storage area within the CPU. All data must be represented in a register before it can be processed: MAR MDR IR PC A

Accumulator

Disk Cache

-a portion of RAM used to speed up access to data on a disk

-before reading the data from the disk, the operating system first checks if the data is in the cache

-data can be accessed from RAM much faster than from a disk

-disk caching increases performance

-may also predict what data is needed next so they can place that data in the cache ahead of time

RAM Cache

-RAM cache memory is (part of the main store) between the CPU and the rest of memory

-use of cache memory reduces processing time

Device Drivers

-required when devices (printers, PCs, etc) need to communicate

-enables devices to interface with each other

-a driver is a piece of software that ensures device and PC understand each other

0 marks

One character requires one byte, while 6 characters require six bytes (48 bits).

2) Complete the table below to show the value of each variable when the algorithm is performed on the data given. [2]

Line 6: 4, 81, 4, true

3 marks

5 rather than 4 in both columns i and X. Follow algorithm within the loop until it is ended.

5 a) Giving an example in each case, define the computer terms bit and byte. [2]

0 marks 

Again: One character requires one byte, while 6 characters require six bytes (48 bits).

7) Discuss the differences between fixed and variable length records. [6]

5 marks

Give some examples of when each type may be used (e.g. hospitals).

8 a) Write down one example of a meaningful identifier from the algorithm and explain why programmers use meaningful identifiers. [2]

1 mark

Out of "set Found = false" the "Found" part is not needed.

12) Amend the algorithm to correct this problem. You may cross out and replace any lines of the algorithm. [2]

0 marks

(NumberRemaining < 10) rather than (NumberRemaining <= 0)

13 b i) Describe a suitable validation check... [2]

0 marks

Wrote the description for a type check, but instead called it a format check.

15 a iii) to temporarily store data or control information used for a specific purpose [1]

0 marks

Write down one example of a self documenting identifier from the algorithm. Describe in detail why programmers use self documenting identifiers.

o Should explain its use to the programmer returning to the code or a new programmer

o Highest Even is an identifier that stores the highest even number

o Number Output is the even number calculated and output

It is beneficial for programmers to use self documenting code rather than anything random such as X or Y

If algorithm is given, try to use an example from it

Write down an example of repetition from the algorithm opposite. Describe in detail the purpose of repetition in computer programs.

2/3

Create an AutoExec macro

If you have already created a macro that contains the actions that you want to occur when the database starts, just rename the macro AutoExec, and it will run the next time that you open the database. Otherwise, follow these steps to create a macro:

On the Create tab, in the Macros & Code group, click Macro.

In the drop-down list at the top of the Macro Builder, select the action that you want to perform. If applicable, type the appropriate values in the argument boxes.

Repeat step 2 for each additional action that you want to occur.

Click Save, and in the Save As dialog box, type AutoExec.

Option Compare Database

Option Explicit

Private Sub cmbActivities_BeforeUpdate(Cancel As Integer)

Me.cmbSwimming.Visible = False Me.txtDistance.Visible = True Me.txtSpeed.Visible = True

If Me.cmbActivities = "Running" Then Me.cmbSwimming.Visible = False Me.txtDistance.Visible = True Me.txtSpeed.Visible = True

ElseIf Me.cmbActivities = "Cycling" Then Me.cmbSwimming.Visible = False Me.txtDistance.Visible = True Me.txtSpeed.Visible = True

ElseIf Me.cmbActivities = "Swimming" Then Me.txtDistance.Visible = False Me.txtSpeed.Visible = False Me.cmbSwimming.Visible = True End If

End Sub

Private Sub cmdNew_Click()

End Sub

Private Sub txtDate_BeforeUpdate(Cancel As Integer)

If Me.txtDate = "" Or IsNull(Me.txtDate) Then MsgBox ("Please enter date.") Cancel = True 'force the cursor to remain inside the textbox End If

End Sub

Private Sub txtDistance_BeforeUpdate(Cancel As Integer)

If Me.txtDistance = "" Or IsNull(Me.txtDistance) And (Me.cmbActivities = "Running" Or Me.cmbActivities = "Cycling") Then MsgBox ("Please enter distance.") Cancel = True 'force the cursor to remain inside the textbox End If

If Me.txtDistance <= 0 And (Me.cmbActivities = "Running" Or Me.cmbActivities = "Cycling") Then MsgBox ("Please enter valid distance.") Cancel = True 'force the cursor to remain inside the textbox End If

End Sub

Private Sub txtFinishingTime_BeforeUpdate(Cancel As Integer)

If Me.txtFinishingTime = "" Or IsNull(Me.txtFinishingTime) Then MsgBox ("Please enter finishing time.") Cancel = True 'force the cursor to remain inside the textbox End If

If Me.txtFinishingTime <= 0 Or Me.txtFinishingTime <= Me.txtStartTime Then MsgBox ("Please enter valid finishing time.") Cancel = True 'force the cursor to remain inside the textbox End If

End Sub

Private Sub txtStartTime_BeforeUpdate(Cancel As Integer)

If Me.txtStartTime = "" Or IsNull(Me.txtStartTime) Then MsgBox ("Please enter start time.") Cancel = True 'force the cursor to remain inside the textbox End If

If Me.txtStartTime <= 0 Then MsgBox ("Please enter valid start time.") Cancel = True 'force the cursor to remain inside the textbox End If

End Sub

Private Sub txtWeight_BeforeUpdate(Cancel As Integer)

If Me.txtWeight = "" Or IsNull(Me.txtWeight) Then MsgBox ("Please enter weight.") Cancel = True 'force the cursor to remain inside the textbox End If

If Me.txtWeight <= 0 Then MsgBox ("Please enter valid weight.") Cancel = True 'force the cursor to remain inside the textbox End If

End Sub

Private Sub cmdMenu_Click()

DoCmd.OpenForm ("frmMenu")

End Sub

Private Sub cmdSubmit_Click()

Me.txtActivityTime = Me.txtFinishingTime - Me.txtStartTime

If Me.cmbActivities = "" Or IsNull(Me.cmbActivities) Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If If Me.txtDate = "" Or IsNull(Me.txtDate) Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If If Me.txtStartTime = "" Or IsNull(Me.txtStartTime) Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If If Me.txtFinishingTime = "" Or IsNull(Me.txtFinishingTime) Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If If Me.txtDistance = "" Or IsNull(Me.txtDistance) And (Me.cmbActivities = "Running" Or Me.cmbActivities = "Cycling") Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If If Me.txtWeight = "" Or IsNull(Me.txtWeight) Then MsgBox ("Please fill in missing forms.") Exit Sub ' exit subroutine End If

If Me.cmbActivities = "Running" Then

Me.txtSpeed = Me.txtDistance / Me.txtActivityTime

Me.txtCaloriesBurned = 472 / 5 * Me.txtSpeed Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight End If

If Me.cmbActivities = "Cycling" Then

Me.txtSpeed = Me.txtDistance / Me.txtActivityTime

Me.txtCaloriesBurned = 354 / 11 * Me.txtSpeed Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight End If

If Me.cmbActivities = "Swimming" And Me.cmbSwimming = "Backstroke" Then Me.txtCaloriesBurned = 413 / Me.txtActivityTime Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight

ElseIf Me.cmbActivities = "Swimming" And Me.cmbSwimming = "Breaststroke" Then Me.txtCaloriesBurned = 590 / Me.txtActivityTime Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight

ElseIf Me.cmbActivities = "Swimming" And Me.cmbSwimming = "Butterfly" Then Me.txtCaloriesBurned = 649 / Me.txtActivityTime Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight

ElseIf Me.cmbActivities = "Swimming" And Me.cmbSwimming = "Freestyle, slow" Then Me.txtCaloriesBurned = 590 / Me.txtActivityTime Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight

ElseIf Me.cmbActivities = "Swimming" And Me.cmbSwimming = "Freestyle, fast" Then Me.txtCaloriesBurned = 413 / Me.txtActivityTime Me.txtCaloriesBurned = Me.txtCaloriesBurned / 80 * Me.txtWeight

End If