Category Archives: Computing Higher

2. Software Development, Computing Higher

ADITDEM lesson!

We began the lesson discussing our coursework. We went over ADITEM.

Analysis:
is the understanding of the problem, which the systems analyst would perform. The systems analyst would use their techniques to gain information and produce a problem specification of basically what the customer wants the program to do.

Design:
The design in ADITDEM is a plan of the program will do. Two types of design are pseducode and structured diagrams. These designs involve steps taken to make the program. This makes it smaller and easier to understand.

To help us understand the concept of design we were given a task. We were given two pieces of paper, with which on one we had to make a shape/diagram e.g. paper aeroplane or oragami and on the other we had to write our steps taken to make this shape/diagram. We than were given a final piece of paper and swapped our steps with someone else. Each of us had then to use that person’s steps and make their shape. This task proved very difficult as hardly anyone’s shape was the same as the right one. This task told us that in design our pseducode and structured diagram had to be very detailed to work. We decided we need a way to help us design. Rules!
Our pseducode had to make rules. In our coursework the design stage is worth 6 marks. Our design must be understood by anyone to pass. It is worth looking over.

Implementation:
We use visual basic in class for implementation, however, there are a lot more. There are various, different languages and different sources.

Testing:

  • exceptional – values not expected, defensive program, assume the programmers don’t understand e.g. always check and verif
  • extreme – allowed but at limits, right on limit,  sensible data, e.g. you could enter the wrong PIN as long as it is in the rang
  • Normal – allowed e.g. enter a number between 1 and 5. The number 3 will be accepted.

TEST TABLE:
A test table will check the limits of the program e.g.

PRESSED          EXPECTED          ACTUAL
yes                          quit                        quit
no                       don’t quit           don’t quit

The program works, however, we cannot be sure of errors.

2. Software Development, 6. External Sites, Computing Higher

Software Development 2010 – where we are

You should find the powerpoint I used in class attached at the bottom of this entry.  Here are some of the example I used in class.

Squeakland – the home of etoys

Sugar on a stick – OLPC’s OS

Please see the PT ICM blog for minecraft

Software Development Catchup

The code we have created so far at the end of the period is given below, please see if you can finish it off.

Option Explicit
Private Sub CmdStart_Click()
‘Set up variables
Dim multiple As Integer
‘Get Multiplier from user
Call GetValue(multiple)
‘Display table
Call DisplayTable
End Sub
Private Sub GetValue(ByRef intvalue As Integer)
intvalue = InputBox(“Please enter the value”)
End Sub
Private Sub DisplayTable()
End Sub
Computing Higher

Printers and screens

Today we learned all about printers and all the different types that you get, including their cartridges and about different types of screens.

Mr Stratton began by recapping what we had talked about in the previous lessons, cameras, analogue to digital converters, videos etc.

He began the lesson by taking the printer to pieces to show us the cartridge and explained that not all of them contain bombs. Ink-jet printers are based on a mixture of three different types of technology : continuous flow ink-jet, liquid ink jet and phase-change ink-jet. Mr Stratton then went on to explain about how liquid ink-jet works. Liquid ink-jet works by squirting tiny drops of ink onto the paper, the ink is firstly heated up by the electric current through a coil, this creates a bubble which then forces the ink from the printer to the paper.
We then went on to talk about how laser printers work. Mr Stratton went on to explain that the lasers “write” a page image onto a special drum as an electrostatic charge, the charged drum draws the toner particles which then transfers onto the page to make an image.

In today’s lesson we also learned about different types of screens/monitors. We learned that multi-screen monitors are used for desktop computers and are based on technology which is similar to that of a TV screen, these both use a CRT-Cathode Ray Tube. CRT improves the quality of the images on screen. A Cathode Ray Tube is a miniature version of the lights that are in a classroom and are meant to last roughly 10,000 hours but because of the size and different parts required to make it work it turns out to be reasonably complicated and expensive to make. TFT-Thin-Film Transistors are much more robust as they are a lot cheaper to produce and do not take as much time to make. This means that overall it would be practical to use a TFT monitor rather than a CRT just because they are a lot more reasonable in price, however, the CRT is actually better because the screen is brighter and far more realistic.

We then began to have a natter about how TFT screens brake if they are twisted unlike the latest LED screens that are able to be moulded for flexibility. So if you want a laptop that rolls up like a newspaper in your pocket you might want to wait till they are released.

To end the lesson Mr Stratton then began to talk about- “the project“. He spoke about how the old exams used to be and how you could pick your own subject and work away at it, which he loved, and how it has now changed so that we all have to do the same, which he doesn’t really like that much. He also mentioned what he aims to do tomorrow-give out two different projects to the separate groups, tell us to decide what is good and which is bad, give them a mark and then give us the marking scheme= tomorrows lesson.

That’s all folks. 🙂

1. Computer Systems, 3. Multimedia, Computing Higher

Cameras and printers

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Today we learned about cameras.

We learned that different types of will have different frame rates. Cheap £20 phones will have very poor video quality. HD video on a phone is better, a digital camera is better than that, a professional camera will be better and a proper TV camera will produce the best quality.

Some cameras have a digital delay.

We also learned that AVI stands for Audi Video Interface. AVI is a windows base format which interleaves video sound and video data.

QuickTime – CODEC was developed by apple but can be used by both Mac and PC. It, like AVI, interleaves sound and video data.

We learned that accurate depends on compression technique, frame rate and resolution.

Speed – Hardware must be fast enough to cope with stream of to memory and to the hard disk.

A digital TV tunes can turn a computer into a digital TV. Good for people who want a computer and TV.

Film replaced by an array of photosensitive cells. Images stored electronically using photosensitive diodes called shared coupled devices (CCDs). The intensity of light is recorded in an image.

Analogue values converted to digital using ADC. Compression usually takes place. Bitmap files are turned into JPEG.

Accuracy is measured in pixels and mega pixels. More is better and less is worse. The accuracy depends on the array of photosensitive cells. The more sensors the smaller they are the higher the resolution.

But depth is in proportion to the number of colours that can be represented. Bit depth is very important on cameras.

Ink is very advanced and difficult to make. That is why it is to expensive.

Inside the pint of a cartage there is a chamber. It is heated and the liquid expands into a bubble. This bubble slowly pops and that is how ink is printed.

Computing Higher

Scanners

Today in Class we learned about scanners and why they are used.
The period started with mr Stratton talking about the previous lesson in which Peripherals mainly the keyboard were discussed.

The Qwerty keyboard has its roots in mechanical typewriters, this type of keyboard was designed in on order to slow down operators in order to avoid jamming the keys.

After a recap on the previous lesson Mr Stratton started discussing with the class about scanners .
A flat bed scanner allows for up to a4 size documents, the document is placed downwards on a glass panel and then scanned, a light beam reflects the light form the document and the photocells measure the light reflected. Also when scanning Analogue data it needs to be converted to digital.
Mr Stratton also told us that Modern Scanners use high bit depths to allow high resolutions.
Furthermore we learned that images that are being scanned must match their purpose meaning that there is no point in scanning at a resolution of more than 75 dpi for a screen based display. Likewise there is no point in scanning at 600 dpi for a printer that is rated at only 300 dpi.

Then we learned about the accuracy of scanners. In scanners accuracy is measured by how close the image is to the original. Resolution was described as the dots per inch (dpi) that can be detected by the scanner hardware.
For example a 600 dpi scanner has 600 photocells per linear inch.
Also the Bit depth of a scanner is usually 24 bits meaning it consists of 8 red bits, 8 green bits and 8 green bits.

Mr Stratton then continued the lesson by teaching us about the capacity of scanners. Such as there is little internal buffering and they rely on different techniques to transfer the data. Also storage can be high for example A4 page at 600 dpi requires 33.28 mb for 8 bit and around 100 MB for full colour.

Then Mr Stratton spoke about the cost of Scanners which have dropped dramatically in recent years and bundles software is often the major selling point.

The towards the end of the period Mr Stratton taught us briefly about sound.
Naturally occuring sound- is analogue in form. To input sound to a computer software samples the incoming signal and then proceeds to convert the signal into digital form and then usually compresses the file.
Then at the end of the lesson we were told to make some music using www.jamstudio.com in order to show us how the process works.

The End!

Computing Higher

Today’s Lesson ((:

The lesson began with the talk of yesterday’s lesson. Unfortunately I was not in so I can not comment too much about it.

But pupils had a problem that they could not implement a program, some made the program from scratch which was a waste of time as they could take the program before hand and change this. This is useful as it does not waste time going through a huge code again.

A program was described as Lego. You can build it and then finish it, it may look pretty but you can add pieces or take away pieces to make it a lot more complex and intricate. This idea goes with a program; you can also do this to a program which will make the program better.

The class was introduced to procedures. We had to understand the input and output and this was shown by a structured diagram- which is similar to pseudcode, but is a visual version of it. They can get complex on the other hand which is a disadvantage of using one.

Now using one, every one knows that efficiency is relevant! If we use the same part of a program then we don’t have to keep testing, error checking or even re-writing a program. This saves time and money and makes life easier…the phone went.

To start our structured diagram, we wanted a program that would add 2 numbers together and displayed the answer. It shows each different part of the program using boxes. It looks very similar to a family tree, with the sub-programs expanding down and then along to the right.

Parameter passing consists of a Global Variable (which is a variable which is used throughout the program) and a Local Variable (which is used at one part of the program). The input and output of the program we were writing contains a By Val and a By Ref. By Val is a copy of the variable (read only). And a By Ref is the actual variable (read + write) which can be changed at any time.

An example of parameter passing

1) Set up variables (BY REF)
Output NumA, NumB

2) Get 2 numbers
Input/Output NumA, NumB

3) Display Answer (BY VAL)
Input NumA, NumB

The phone wrung one last time before we left.

By Corrie 😛 x