Vector Graphics

There are two types of graphics, bit-mapped and vector. Vector graphics are made through a series of shapes which allow the maker to re-size the image(which you cannot do with bit-mapped) without any loss in quality making them resolution independent  To store the image only the attributes of the image are stored not the colour of the pixels(like in bit-mapped)  e.g. the coordinates of the shapes, line width, shape colour, radius etc. Due to these only being stored the file size tends to be lower than bit-mapped .If the image is stored as a vector the appearance of the image will be better if the monitor display has a higher resolution, with bit-mapped the resolution is fixed and doesn’t change if the monitor has a better resolution. Vector graphics are commonly found in images like logos and billboards as they will be scaled to fit various items and therefore they wont have any loss in quality when the image size is changed. Some types of formats used to store vectors are SVG (Scalable Vector Graphics)  and VRML ( Virtual Reality MarkUp Language).


Technical Terms (sound)

Clipping – Clipping is the process of removing sounds that are distorted. This has to be done as the track can only be recorded to a maximum volume before distortion occurs.


Stereo – This is when two tracks are played together which creates the feeling of the music coming from a specific direction.


Fade – This is the process in which the volume and frequency is gradually lowered or raised.

Surround sound – This is a way of improving the experience you have when listening to music as it will involve more speakers so it wont be heard better from one direction

Bitmapped graphics – technical terms

Dithering: this is the process used to trick the human eye into seeing new colours and shades by slightly fading the already present pixels. If you look closely at the picture you can see the different colours even though that colour isn’t actually used, it is just a faded form of the surrounding colours.

Anti-aliasing: this is used to give picture a more smooth look so it becomes more appealing. When a computer doesn’t have enough resolution for the picture you can see the image has a blocky look around the border. Anti-aliasing blends the background colour with the colour of the border pixels to give it a more satisfying look.

Increase resolution (re-sampling):  this involves changing the pixels dimensions but will result in loss of quality. It uses a process called interpolation which causes blurring when the size of the image is changed.

The Processor

The processor is essentially the brain of the computer that controls everything that goes on. Processors can be found in a lot of everyday items such as microwaves, phone and washing machines. The ALU (arithmetic and logic unit),part of the processor, carries out the calculations and logical operations such as AND,OR,NOT. Each one of the memory address locations must be unique so they are easy to find. The control unit is the processor works with the fetching,decoding and executing of instructions that can be as simple as changing a page. The Registers act as temporary storage locations like memory but are much faster. The MAR is the memory address register which is used to keep the address of a memory location where data is kept. If you want to write data the MAR has to get the address of where it needs to go and the MDR (memory data register) which is the data that is being written. Once done the write line on the control bus activates and the data in MDR is sent to the address specified in the MAR, along the data bus. For reading the MAR needs the address of where the data is located and once that is achieved the read line on the control bus is activated. After doing so the address bus finds where the data is and the data is sent back through the data bus to the MDR. The data is then decoded and executed. These read and write operations are used to load instructions and are found in programs as there are lots of instructions within them. This is known as the fetch and execute cycle. The control bus always has 4 functions – read, write, clock and interrupt. Read tells the memory the data is to be sent to the processor from a specified memory location. Write tells the memory that the data is to be sent and stored to a specified memory location. Clock regulates the speed the information travels at by generating a constant pulse. Interrupt ensures that if something interrupts the current task the task will be put on hold and stored in a temporary memory location called the stack and will be returned to once the interruption is complete. The interruption could be caused by things being put into the computer such as USB or other programs being loaded. 

Vector and Bitmapped graphics

WIth bitmapped images they are stored through the pixels they are made up of which takes up a lot of memory but with vector graphics the image is only stored through the attributes it consists of. Due to vector graphics having to store less than bitmapped the file size tends to be smaller but can change depending on the image itself. bitmapped is the type of image that is tended to be used with most images as it gives a more vivid and clear picture and vector graphics are used for things like logos. Vector graphics have advantages over bitmapped such as they can be re-sized, smaller file size and if it is sent to another location the resolution of the image is able to change if the location has a higher resolution. The advantages to bitmapped is that you have the ability to edit your images to pixel level, so you can make changes in detail and the file size of the image is fixed.

Data Representation

Positive numbers- These are represented on a computer using binary. In a 8 bit binary system meaning the number is between 0 and 255 the numbers 1 and 0 are put under the correct numbers in the binary system so it adds up to the decimal number e.g.

128 64 32 16 8 4 2 1
0    0   1   0  1 1 0 1 = 45

Negative numbers- These can be represented through either two’s compliments or signed bit. Signed bit uses the starting number to determine wether the number is negative or positive. 1 = negative
0 = positive. This causes an error though as it can produce 0 and -0. The better method is to use two’s compliment. This is done by getting the positive form of the number in binary, changing all the 1s to 0s and 0s to 1s then adding 1. e.g.

00101101 = 45
11010011 =-45

Real numbers are produced in binary by using floating point representation. If the number is a fraction a decimal point is put into the binary to represent it, as after the decimal point the numbers go 1/2, 1/4, 1/8 etc. however the computer doesn’t understand decimal points which is where floating point representation is used. The decimal point is moved all the way to the left leaving the binary number without it and calling it the mantissa. The mantissa is then x by 2 to the power of how many places it was moved (exponent).e.g.

mantissa= 00010101 exponent = 5
00010101 x 2^5

To represent text we use ASCII (American standard code for information interchange) which gives each character a unique, 7 bit, binary code. However ascii can only store 128 characters so extended ascii was made. This uses 8 bits to store a character and can store 256 characters. However there are languages that have more that over 256 characters so they cant use this system which is where unicode is used. Unicode uses 2 bytes (16 bits) to store characters. This can store 65536 characters.

Bitmapped graphics – A screen is made up off lots of tiny dots called pixels. Each individual pixel stores colours. The more colours the more bits used to store the colours in each pixel. With more pixels the quality of the image is increased and with more colours in each pixel the finer the detail. Each pixel holds a binary number which represents the colour it holds. with more colours you need more binary numbers so you need to increase the bit size to get bigger numbers. 1 bit only stores 2 colours, black and white. 2 bits 4 colours etc. true colour(the most colours a human can recognise) is 24 bits(3 bytes) which is 16777216 colours.

Standard algorithms

The two standard algorithms I will be talking about is count occurrences and linear search.

Count occurrences is a type of algorithm in which a number that is defined by the user will be run through a list that is either also defined by the user or hard coded into the program. The amount of times the number is found will be relayed back to the user once all of the list has been searched.

Linear search also gets a number from the user and runs it through a list(defined by user or hard coded) and the program will look through the code and find where it is. Once done the program will tell the user what position in the list it is.