1.4c Secondary Storage Media

Differences:

• Optical vs. Magnetic
• Max Size
• Sequential vs. Direct Access
• Read Speed
• Portability

1.4b Types of Primary Memory

ROM (Read-only)

Small permanent memory that holds a small program called the bootstrap - Looks for OS when "Booting"

RAM (Random Access Memory)

• Holds OS / Data / Programs that are IN USE.

• Emptied when PC is switched off.

ROM
  - Non-volatile (Doesn't Change)
RAM 
- Volatile (Able to Change)

1.4a Control Unit, Memory Unit, and Arithmetic Logic Unit

Arithmetic Logic Unit:

• Does Maths
• Works out Logic (IF, Else)
• Holds I/O while Control unit decides what to do

Memory Unit (Stores)

• Holds all the instructions to be used
• Holds all the data to be used

Control Unit

• Decides next instruction
• Gets it
• Deciphers it
• Tells the other parts what they need to do.

1.3j Back up vs Archiving

Backing up

• Store data for current data that may be required data that they are currently need (Short term)
• Backs up data that can be accessed fast
• done as often as possible

Archiving

• Done less frequency
• Cheaper media
• long term

1.3g Different Storage Types

Saving to serial storage:
Tape

• No storage
• slow to load
• takes to long to find data
• Brilliant for saving
• order that they arrive are saved
• cheapest method of saving
• physical method of storage

Sequential

• looks whats on the and saves in order
• slows down saving
• much quicker to find data

Index Sequential

•  Very fast
• Access to data that uses index's through different menus
• On credit card = hashing algorithm

Example:
Credit card

• type of card- 
1. visa 
2. country
3. banks
4. branches

Random Access

• following a hashing algorithm to decide where to store every piece of data is stored in a specific
• If it is not complicated enough it can result in clashes
• Fast

1.3 Fixed length records

Each field limited to:

• Name -
• 255

• Age - 
• 8 (Int)

• Price - 
• 16 (Dec)

• Boolean - 
• 1 bit

1.3 LIFO & FIFO

FIFO:
First In first Out
Queues are tubes
Queue have two pointer, a Head and Tail pointer



Example:
Print Queue














LIFO
Last In First Out
Stack - writes down the return address when a procedure is called
Only one pointer
Example: 
stack of paper

Do while save = false
slot = slot + 1
Get Array (Slot)
If Array (Slot) is empty
then save data
saved  = tru
slot = slot +1
loop
If saved = false then
 msgbox ("not saved")

Program 9.4

Program 9.4 has two parts

Public Class Form1

    Private Sub btnNewName_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNewName.Click
        Dim Name, NewName As String
        Name = txtname.Text
        NewName = UpperCaseFirstLetter(Name)
        lblNewName.Text = NewName
    End Sub
End Class

Part to (Module part)
Module Module1
    Function UpperCaseFirstLetter(ByVal OldString As String) As String
        Dim FirstLetter As Char
        Dim NewString As String
        FirstLetter = Char.ToUpper(OldString.Substring(0, 1))
        Mid(OldString, 1, 1) = FirstLetter
        NewString = OldString
        Return NewString
    End Function
End Module

Program 9.2

Option Strict On
Public Class Form1
    Dim Total As Integer
    Dim NumberOfMarks As Integer

    Private Sub btnOK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOK.Click
        Dim Number As Integer
        Number = CInt(txtMark.Text)
        lstMarks.Items.Add(Number)
        Call ProcessOneNumber(Number, Total, NumberOfMarks)
        btnShowMean.Enabled = True
        txtMark.Text = ""
        txtMark.Focus()

    End Sub

    Private Sub btnShowMean_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnShowMean.Click
        Dim Mean As Double
        Call Calcmean(Total, NumberOfMarks, CSng(Mean))
        txtMean.Text = CStr(Mean)
        txtMean.Visible = True
        lblMean.Visible = True
        txtMark.Enabled = False
        btnOK.Enabled = False

    End Sub

    Private Sub btnQuit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnQuit.Click
        Me.Close()
    End Sub

    Private Sub txtMark_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtMark.TextChanged
        btnOK.Enabled = True

    End Sub
    Sub ProcessOneNumber(ByVal ExamMark As Integer, ByRef MarksTotal As Integer, ByRef CountOfMarks As Integer)
        MarksTotal = MarksTotal + ExamMark
        CountOfMarks = CountOfMarks + 1
    End Sub
    Sub Calcmean(ByVal MarksTotal As Integer, ByVal CountOfMarks As Integer, ByRef Average As Single)
        Average = CSng(MarksTotal / CountOfMarks)

    End Sub
End Class

Program 9.3

Public Class Form1

    Private Sub btnCalcInterest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalcInterest.Click
        Dim Interest, AmountInvested As Decimal
        Dim RateOfInterest As Single
        Dim Years As Short
        AmountInvested = txtamountinvested.text
        RateOfInterest = txtInterestRate.Text
        Years = txtYears.Text
        Interest = CalculateInterest(AmountInvested, RateOfInterest, Years)
        lblinterestrate.Text = Format(Interest, "Currency")

    End Sub
    Function CalculateInterest(ByVal Principal As Decimal, ByVal InterestRate As Single, ByVal numberYears As Short) As Decimal
        Dim Interest As Decimal
        Dim Year As Short
        Interest = 0
        For Year = 1 To numberYears
            Interest = Interest + ((Principal + Interest) * InterestRate / 100)
        Next Year
        Return Interest
        CalculateInterest = Interest
    End Function


End Class

Program 9.1

Public Class Form1

Private Sub hsbRed_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ScrollEventArgs) Handles hsbRed.ScrollMe.BackColor = ColorTranslator.FromOle(RGB(hsbRed.Value, hsbGreen.Value, hsbBlue().Value))End Sub
Private Sub hsbGreen_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ScrollEventArgs) Handles hsbGreen.ScrollMe.BackColor = ColorTranslator.FromOle(RGB(hsbRed.Value, hsbGreen.Value, hsbBlue().Value))End Sub


EndPrivate Sub hsbBlue_Scroll(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ScrollEventArgs) Handles hsbBlue.ScrollMe.BackColor = ColorTranslator.FromOle(RGB(hsbRed.Value, hsbGreen.Value, hsbBlue().Value))End Sub Class

Procedures and Functions

A function is a set of commands which return a value. For example, if we had a function called “add” and passed it two “parameters” ‘a’ and ‘b’ and it added ‘a’ and ‘b’ together, then the value it returned would be “a + b” and we could write our function something like:

add(a, b) {
total = a + b;
return total;
}

What is a procedure?
A procedure could be considered as something which is a set of commands which do not return a value.

The easiest way to think of a procedure is it is a “doing” thing and a function is a “calculating” thing. For example:

procedure open_door(door_id, angle_to_open) {
                start_door_opener(door_id);
                while (find_open_angle(door_id) < angle_to_open) {
                                continue_opening(door_id)
                                }
                stop_door_opening(door_id);
}

So, we have a procedure which opens a door. It doesn’t “return a value”, because it is doing something. We pass it 2 parameters
 the ID of the door to open door_id2.        how far to open the door. angle_to_openThe procedure then starts opening the door, and continues to open the door while the function “find_open_angle” is less than the requested “angle_to_open”.

What are WIKI'"s, Blog's, Micro Blog's and RSS

Wiki: A web-based mechanism to store information, it can be edited by many different users (sometimes using an authorisation system). The best example is http://www.wikipedia.org/
Blog: A web-based mechanism to allow an open discussion on a topic. http://www.farq.co.nz/ (for a laugh!) Alternatively, you could try a more traditional blog site e.g. http://transportblog.co.nz/
Micro blogging: Similar to a Blog, except the comments are usually smallier in size. An example would be http://twitter.com/
RSS: “Real Simple Syndication”. It is a format used to disseminate information in a standard way. It is based on XML. Most news websites have RSS feeds available, e.g. http://snowreports.co.nz/syndication/xml/allfields_brief.cfm

Prep

Name example
how does it work? RE: people and info
an example of how it can be used and who uses it

wiki
blog
microblogging
RSS

Hardware Software

Everything that happens in a computer goes from:
Input - Processor - Output         
             //
       Storage

The CPU infact does not connect directly with the hard drive but instead with the RAM stick. As trying to connect the CPU to hard drive is like talking to someone from a jet plane to a bike.

Software:
Software = sets of instructions which tell the system how to do something. These instructions are collected together in a workable group which is called a program.

Operating system

• User interface software
• Provides a GUI
• Provides a Platform for apps top go on it
• Middle ,am between apps and hardware i.e. Word does not know anything about printers but OS does.
• translate software (TS)
• An OS provides its own TS
• Translate high level language into Machine 'Code' - Source code to the object code
• Untilities
• Allows you to change the system to a certain extent
• Applications
• Common Applications (Any app that is used around the world
• iPhoto
• MYOB
• Genetic Applications (Any piece of software that is used for multiple applications)
• Word
• Power Point
• Custom Software (unique, it is only written for a unique task)
• Off the Shelf Software (bought from a shop)
• Downside
• Paying for all the software you don't use