System
A system is an assortment of software and hardware that, from physical or digital input, creates an output that is intended and useful to you. For a system to work you first need an input, then for the system to process the information, then for you to get the output. If a system has no output it is useless.
Reliability
Reliability is the measurement for how much faith and trust you have in a system working. If a system you use will work without fail it is reliable however if your system has a chance of breaking then it isn't reliable, however reliability cannot be guaranteed. This can be extremely dangerous as some systems (like in aeroplanes) could result in death if they aren't reliable.
In most systems reliability is important (you don't want your pc to crash whole doing something) however in some systems that we rely on every day reliability is one of the most vital components. For example on a rocket if the computer failed everyone
Input> Process> Output
Embedded Systems
An embedded system is a computerized system, usually within a larger device that has a specific set of functions or tasks. This could be anything from temperature control in a washing machine to air bags, abs or traction control in a car. Embedded systems are useful because they have low power, low cost and can still have a sophisticated functionality.
Regulations and Data Protection
Regulations exist to protect your identity from being stolen, for example in 2010 in fewer than 6 months $900,000 of one mans debit card was taken out of his account after they put keystroke malware on his computer. "It was nasty," he said, admitting that he even contemplated suicide. "I just couldn't take it. I didn't feel like a man anymore. I was violated and I didn't know what to do."The data protection act contain eight principles that say data must be:
1. Processed fairly and lawfully.
2. Obtained for specified and lawful purposes.
3. Adequate, relevant and not excessive.
4. Accurate and up to date.
5. Not kept any longer than necessary.
6. Processed in accordance with the “data subject’s” (the individual’s) rights.
7. Securely kept.
8. Not transferred to any other country without adequate protection.
The Copyright, Designs and Patents Act says that you cannot take things (like music, films and software) without their permission. 95% of music downloaded online is illegal; 42% of software in the world is illegal; the three most downloaded programs illegally are Adobe Photoshop, Microsoft office and Nero 9; 91% of files on Cyberlockers like Megaupload, Rapidshare and Mediafire are copyrighted material; 2/3rds of bit torrents online are copyrighted material.
http://dataprotectionact.org/1.html
http://www.infographicsarchive.com/interesting-facts/online-piracy-in-numbers-facts-and-statistics/
http://www.infographicsarchive.com/interesting-facts/online-piracy-in-numbers-facts-and-statistics/
Kernel
A kernel is the lowest level in an operating system. It controls the hardware. It manages the inputs and outputs of the operating system. It is also responsible for the management of the hardware like the memory.
Binary Logic
In a Not gate the output is the opposite of the input.
In an OR gate you will always get an output of 1 unless both inputs are 0.
In the AND NOT gate the output is always the opposite of the and gate (where there was once a 0 there is now a 1)
Binary is a number system using only ones and zeros. One being ON and zero being OFF. These systems also use logic gates. These are used to manipulate the signals.
Ram
Ram is "random access memory" and the main source of memory in a computer system. RAM is needed to run any application or operating system. This means that the more RAM the more applications can run at any one time resulting in better performance. When a program is loaded it goes from the hard disk to the RAM then finally to the CPU via the cache,
There is two types of RAM:
Dynamic RAM- Only has one transistor and capacitor that can hold a small charge for a few milliseconds.
Static RAM- does not need to be refreshed as they have four or five transistors that have a constant charge.
Input and Output Devices
An input device is anything that can control the output device. Without input or output devices you couldn't control a computer or see/hear etc. what the computer wants you too.
An example of an input device is the mouse which navigates your pointer on the screen (output device).
Some input or output devices are for users with specific needs, for example the braille keyboard which is a specialist keyboard for people who have a visual impairment and cant see a normal keyboard.
Secondary Storage
Secondary storage is a non-volatile way to store data. your primary storage is your hard drive but then your secondary storage is another way to store your data outside your hard drive. you do this because secondary storage can be useful for many reasons.
1. Portability, You can buy a small 16GB usb stick for £7 which you can carry around with you wherever you go.
2. Speed, You can buy a SSD for £45 which are much faster and reliable than your normal hard drive.
3. Durability, most secondary storage is more durable than normal hard drive.
Binary
Binary is a number system using just ones and zeros to represent all denary numbers in base 2. Numbers form 1 to 15 are represented in four numbers or a "nibble" and numbers 15 to 255 are represented as 8 numbers or a "bite". The four or eight numbers represent denary numbers like this:
128/64/32/16/8/4/2/1
Therefore an example would be 128=10000000, or 50= 00110010.
Hex
Hex is a base 16 number system used to represent binary in a simpler form. The numbers from 0-9 are represented as themselves but from 10-15 are represented as letters. Hex works by the first number being what you imes by 16 and the second number is what you add on after, for example the hex number 32 means 3*16+2=50.
ASCII
ASCII (American Standard Code for Information Interchange) is a set of 127 codes that represent all characters on an English keyboard (56 UPPER and lower case alphabertic characters, all numbers 0-9, 32 punctuation and other symbols (space, !"£$%^&*()_) and 32 codes reserved for non-printable control codes) there is also an additional code for "null" (00000000). ASCII was first used for telegraph systems in the 1960s.
Instruction Sets
An Instruction Set is a set of programming instructions, which allow a computer system to carry about commands necessary for operation. Instruction Sets vary by the design of a processor. A program instruction has two parts, the instruction part that tells the CPU what to do (operator) and the data part that the CPU what to apply the operation to (operand). When the CPU fetches the data from the memory it cannot tell the difference between instructions and data but does what it expects to based on the program its running.
File sizes
Bit- The most basic unit of information, most commonly a 1 or a 0
Nibble- 4 bits
Byte- 8 bits or 2 nibbles, can represent numbers 0 to 255
Kilobyte- 1024 bytes
Megabyte- 1048576 bytes or 1024 kilobytes
Gigabyte- 1024 Megabytes
Terabyte- 1024 Gigabytes
Images
Images are represented digitally in binary where each bit represents a pixel that each have a different colour. Images stored like this are called bit mapped images, the more pixels in a given area the higher the resolution of the image, giving it a higher quality. The higher the resolution the higher the file size as well because there are more bytes.
Colour depth is the number of colours that can be used to represent a single pixel, for example in a 8 bit image there is 256 colours.
Metadata is data about the data; it is useful to provide extra information about a file, in a image this could be: the height, width, colour depth.
Development software
Editors
To write programs you need an editor, they are cut down word processers that do not save formatting . There are some advanced editors that enable "pretty printing" which can detect errors and make them a different colour.
Compilers
Compilers turn high level code back into machine instructions so the CPU can execute them. Each statement in high level code relates to many machine instructions.
Interpreters
Interpreters also convert high level code into machine code but do so a line at a time and execute the code as they go. This uses more RAM and is slower to translate and run one line at a time.
Assemblers
Assembly language is a low level code that has a direct correspondence of one line of code to one instruction. Assembly language changes from one processor to another.
Linker
In one program there can be many different subprograms made by different teams. Linkers combine these programs together to create one big program.
