Bit Patterns & The Binary Number System

To represent binary we use a to the power of 2 scale or measurment. So from 1,2,4,8,16,32,64,128 and doubles each time. We read it from right to left so the opposite to how i just wrote it, so 49 would be represented as 00110001.
To add Binary we can use the old primary school method of addition by putting one binary number above another and adding them that way which makes things easier. If a zero and zero are added then we put down a 0 and move on. If a one and zero are added the result is 1 and dont carry anything. If a one and one are added then the result is 1 and no carry, but if three ones are added then we put down 1 and carry a 1. 

Multiplying numbers, we change all the 1s to 0s from the original binary code then we add a 0 to the end of the code. Finally convert the binary to denary.
To subtract we have to use the two's complement method to convert the number we are subtracting into negative then add them like normal binary numbers.

Systems Life cycle

There are 5 main factors to the development of a system. These are Analysis, Design, Implementation, Testing and finally the evaluation.
Using this Structure it can significantly reduce the risk of the project failing, it losing money/funding or in bad situations the risk of human fatality.
A new system my be needed because new laws have been introduced or a new business opens.
There are a number topics that need to be addressed for each part of the life cycle.
In Analysis:
Is it feasible
Time needed
Skills needed
Etc

For Design:
Buildings
Data inputs and outputs
Hardware/Software

Implementation:
Build the system
Training
Data migration

Testing:
Test Individual parts
Test as a whole
Test the people operating the system.

Finally the Evaluation:
Does it do what it was built for
Fix any problems
Add any new features to optimize it

Sound storing/playing

Sound is either analog or digital. Analog has an infinite possibility of values whereas digital has to be a single value at a time depending on how accurately your measuring it. We speak in analog but computers can only read digital signals so we must first convert our analog voices into digital signals if we want to store/play them throgh a computer. We use a transducer to do this which could be a microphone.
We use a microphone to pick up the analog sound then a ADC converts it to digital signals using the lower part of the possible frequencires it could be. The computer then uses a DAC to play it back through a speaker.
The two factors that influence the quality of the sound are the sampling rate which is how often per second you take a sample of the sound and the sound resalution which is the number of bits availiable to encode each sample you take.
We must sample the frequency of the sound at least twice the frequency of the highest part of the sample; so if the frequency is 200hz - 2khz then we should sample it at 4khz per second and store it using 16, 32,64 bits for each sample.
We use mpeg files to store sound and they discard any sound/frequency that we can't here so the file size is about 10% the size of the original WAV file type.
Digital sound is easier to mix because it can only be certain values and this can help music companies and djs.
To synthesis sound using MIDI we store the instructions to make the sound not the sound itself, this is like storing drawing instructions for vector graphics.

Bitmaps and Vectors

Bitmaps use pixels to display an image. Today we use 24bits per pixel so we can create around 16 million different colours, this is called true colour and is as many colours as we can see with our eyes. The problem with bitmaps is if we use less pixels the images quality gets dramatically worse, so the less pixels we use the worse the resolution is if its the same screen size. Bitmap graphics also take up more memory compared to vector graphics and suffer scaling problems which vector graphics do not.
Vector graphics do not suffer from scaling problems because they are made from a drawing list, this is the geometric information and properties needed to recreate the image. Vector graphics are no good for photos from cameras etc because the camera can't see the image being drawn so has no drawing lists.
Because they use drawing lists instead of pixels the file size of a vector graphic is very small in comparison to a bitmap. This also helps them to load faster from storage.
Lossless compression is a method of reducing the file size but not loosing any information and little quality. This includes telling the computer the number of blocks that are the same colour and grouping them together rather than writing the information for each individually. This is called RUN LENGTH ENCODING (RLE).
The other method is called lossy compression which is removing bits of an image that we won't notice are missing.

Logic Gates

AND logic gate
This will only be activate if both switches are true or both are false, they have to be the same.

 OR logic gate 
This logic gate will only activate if the inputs are different and not the same except if they are both true or 1 then it activates too. So true and false or false and true wouldn't turn it on.

NOT logic gate 
This logic gate will reverse any input, so a false would become a true or a 0 would be a 1.

 

XOR logic gate
Xor gates only turns on if the inputs are different so it's like a stricter OR gate.

NAND Logic gate
 It will activate when both inputs are turned to false/0 or if the inputs are different. Its a combination of AND and the NOT logic gates.

NOR Logic gate
This is like to the NAND gate as it turns on when the inputs values are both false but it won't activate if the inputs are different or both true.

Hardware Devices

Input Devices

Mouse
An LED light is beamed to the surface beneath the mouse which is reflected to a CMOS sensor which calculates the movement on an x-y axis which corresponds to the cursor on the screen. 

Voice Recognition
The computer converts the analog signal from a voice into bits of digital data that the computer can analyze and then guess the word. .

Graphics Table

The tablet picks up the information in the pens tip from sensors behind the screen  in order to determine the position and other information like pressure. Since the grid provides the power to the pen, you don't need batteries for the pen. There can also be lasers across the screen to determine position and pressure.

Digital Camera
It uses lenses to focus light to create an image, it focuses it to a semiconductor device which turns it into electrical data that a computer can use to turn into digital data and an image. 

Keyboard
They electrical parts of a keyboard scan the keys to see if they have been pressed they send a key scan code to the computer which interprets it and puts it on the screen

Smart Card Reader
This reader picks up the binary message in the embedded integrated circuit and reads its content which is usually encrypted for the individual user/business.

Magnetic Strip Reader
The strip on a bank card or I.D  can be read by and electromagnet which activates when the card is slid down it. It tells the computer what it is and the other info about the product is stored in a separate database.

Radio Frequency Identification Reader
Objects will give out a radio frequency wave that will be picked up by a Radio Frequency Identification Reader. The two devices need no physical or electrical contact to transfer data.

 Optical Mark Reader 
 A form is put under a light sensor which reflects light off the paper and it senses the degree of intensity that it is reflected back at. the computer then converts it into digital data.

Optical Character Recognition

Optical Character Recognition systems use scanners to input images of text that is then analysed as digital data which is then used to recognise the characters.

Fingerprint Scanner 
 A bright light scans your fingerprint picking up tiny details which it turns into a digital image. The scanner then changes this digital image into a fingerprint code which is saved and used when the device is activated.

Retina/Iris Scanner 

Works by taking scans of parts of the eye which it then analyses and turns into a mathematical

representation of the eye.

Flatbed Scanner

A pane of glass covers the components of the scanner. Sensors below this pane contain shades of blue, green and red. The sensors run along the object detecting the levels of intensity of the light being reflected. This is then used to make up the image.

Output Devices

Cathode Ray Tube Monitor

 A CRT contains a cathode. It consists of a thick, heated wire that is contained within a glass tube. This tube is vacuum-sealed to stop resistance. The cathode gives out  a stream of electrons into the tube, which travel down. After the electrons are sped up to extremely high speed, they hit a phosphorescent screen at the end of the tube which causes it to glow. 

Color television screens use three electron beams at once. They use one each for red, blue and green. These three colors are used in the phosphor coating on of the picture tube. When each color is struck by its  electron beam, it glows and creates a color picture.  The human eye has been trained into assembling these small dots into a clearer picture. Obviously the more dots per inch, the higher the resolution and the clearer the picture. The highest quality pictures may consist of hundreds of thousands of "dots per inch" creating an extremely clear picture.

Liquid Crystal Display

An LCD screen is made of two pieces of polarized glass which has a Liquid Crystal material between them. A backlight shines light thrugh the first layer of lglass while electrical currents control the levels of light which pass throgh the second that creates the images we see.

Plasma Screen

Plasma TVs use thousands of sealed, low pressure glass chambers filled with a mixture of neon and xenon. Behind these chambers are coloured phosphors, one red, one blue, and one green for each chamber. When heated, these chambers give out invisible UV light. The UV light strikes the red, green and blue phosphors on the back glass of the display making them produce visible light.

Inkjet Printer

This printer sprays ink at high speeds, the printer software has to first process the command. The printer then sprays the paper using dozens of nozzles which print words/images line by line.

Laser Printer

When a text or image is entered into the Computer, it many varying voltages. This controls a LED in the printer. This emitts flashes of laser, when it falls on a charged photoconducting drum. The area corresponding the text or image will either be neutrilized or oppisitly charged. A toner which has the same charge as the background is sprayed onto it. It only sticks to the text or image and is repelled by the background. A fresh paper is now pressed onto the toner and is slighlty heated so that it sticks on the paper.

Types of Software

Software breaks down into many sections but they start with 2 main ones - System software and Application software. System software is used to operate and run hardware where as Application software is used for non-computing tasks such as writing letters. System software then breaks up into operating systems, library programs, utility programs and translators. Operating systems make it easier to operate the hardware and hides most complexities of using a computer- Windows 7. Library programs use commonly used functions such as printing routines and network accessing routines. Utility programs do specific jobs such as virus scans and Translator software that translates high level languages into machine code that the computer can read.
Translators are split into three groups like application software, these are: Assembler, Compiler and Interpreters. Assemblers convert assembly code which is very basic into machine code that computers can read. Compilers covert high level language like java and pascal into machine code but is slow because it does it all at once. Finally Interpreters convert and execute high level language line by line into machine code. I is slow because it is being executed at the same time. Often you will get an Interpreter and a compiler.

Application software is split into 3 groups- General purpose,Special purpose and Bespoke software.
General purpose are applications with many uses such as spread sheets. Special purpose software such as accounting software which isn't commonly used. Finally Bespoke software which is built to specific purpose and is very expensive, these include airport traffic software and the London stock exchange software.