Development software

Development software

EDITORS:    you use editors to write programs, some editors have pretty printing, where it uses different colours for key words and helps you know if you did the code correct

COMPILERS: compilers are for when you use code that are closer to English, this is so you can program easier and is called source code, a compiler converts this source code in to machine code

INTERPRETERS: they basically do the same thing as compilers except they execute the code as you go, this gives you an instant result so is easier to locate any error in your code, they are often used for debugging but they take longer to decode and use more RAM.

ASEMBLERS: in assemblers the programmer is in control of every step, unlike all the others it uses low-level code that means, each language instruction codes for one machine instruction, this means it takes ages to write code for anything.

LINKERS:  linkers basically glue together several codes together, the need for this is because often a program is split into different subprograms that sometimes use different programming tools and languages.
examples include: Ld_(Unix) ; GNU_linker ; Gold_(linker) ;

Data files

Data is organized into sizes, a bit is a binary number, a nibble is 4 bits, a byte is 8 binary numbers or 2 nibbles. A kilobite (kb) is 1,024 bytes A megabyte (mb) is 1024 kilobytes. A gigabyte is 1024 megabytes and A terabyte is 1,024 gigabytes

Instructions

A program instruction is made of 2 parts, the operator or instruction and operand or memory location it should use. For example, a Byte could be split into sets of 4bites, first the operator and second the operand. 

In this example, for first 4bites: 1001 tells the CPU to Add data to the accumulator, 1010 tells it to store data from accumulator into memory location, 1011 tells it to subtract data in location from accumulator.

The second 4bites (memory location): 1100 has 7 in it, 1101 has 4 in it.

So: 1001 0011, 1011 1101, 1010 1110 says: add (0011) 3 too accumulator (total is now 3) then subtract (location 1101) 4 from accumulator (3-4) (-1) then store that data in location 1110.

Text, pictures and sounds

ASCII

In ASCII code, they use binary to make letters punctuation and other characters.

0110 0001 codes for the letter a.   Because it has a total of 10,646 characters, it has to use two sets of bytes for each character.

Unicode isn't just for English, unlike ASCII code, it has characters for all languages, this means it has more characters. 

PICTURES 

to make pictures, you use metadata to tell you the number of binary numbers per pixel (colour depth), height of the picture and width of the picture(resolution).

For example with a 1bit colour depth then 1010 would be black,white,black,white. 

SOUND

sound can be converted into binary numbers that the computer can use by taking samples of frequency every now and then, the more often you take samples the better quality of sound but also increases the file size

Binary and hex

Are number system is currently base code 10 because we have a total of ten fingers

The Column furthest to the right is written as 1 and means 1 times 10 to the power of 0 (1).

If you go one to the left, it's written as 10 and means 1 times  10 to the power of 1 (10).

Each time you go one to the left the power increases by 1.

Binary uses a base code of 2. 

This means instead of ten to the power of whatever, it is 2 to the power of whatever. This means the column to the far right is how many times 1, the next one to the left is how many 2's ...e.t.c.

Computers use binary because there are only to things you could put in each column, 1/0 or on and off.

Hex uses a base code of 16.

This means instead of ten to the power of something it is 16 to the power of something.

The reason we use it to help us understand binary is because each character/column is for each four binary columns.

Binary addition

When adding binary numbers, if there is a 1 and a 0 then in that column you put a 1, if there are no 1's then you put a zero, if there are 2 1's then you put a 0 and carry the 1 to the next column, if there are 3 1's then you put a 1 and carry a 1 to the next column.

CPU

HARDWARE

A CPU, is the brain of the computer system, it stands for Computer, Proccesing, Unit.

It works by looking up what to do with the input, for example you press print, CPU, collects the information needed to do it in the  ROM (Read Only Memory) and then stores that temporarily in the RAM (Random access memory) while it is waiting to process it. It then does what it tells it to do, for example prints the paper.

It is super fast at doing this. This is the endless cycle of fetch, decode and excecute. Fetch the information, turn it into binary code, and do the action/output.

Cache memory is often inside the CPU, it is used to store instructions that are used to repeatedly run programs, it is extremely fast and used to speed up the process.

Binary Logic

Binary is just 0's and 1's,  they can be used to represent all numbers.
it is used because they can be represented easily using an on/off state or switch.
computers use logic gates to manipulate the data.

AND GATE
only 1 if there are two 1's

this table shows the inputs and what the output would be

OR GATE
only 0 when there are two 0's

NOT GATE
output is opposite to input

This is what happens when you combine and  then not

ROM, FLASH, VIRTUAL AND CACHE MEMORY

Input and output

We need input and output devices because to make something happen, you need to be able to give it info on what to do, and it needs to then do something.

Possible input devices could be your body, via 3d sensers, our brains. Outputs can be almost anything, like a picture, video, movement, ordering something online.

Input and output devices, can help people with specific needs a lot.  For example we can communicate with Stephen hawking using eye sensers, in the past, their would be no real way of communicating with him.

If you are paralysed, in the future, they could hook you up to a brain sensor and you could communicate that way.

Order stuff online, even be hooked up to some sort of machine, that you could walk around using, and pick stuff up.

Secondary storage

Stores information when the power is off.

There are 3 main types, optical, magnetic and solid state.

We need it because otherwise we would have to upload data every time we turn it on, but using secondary data, the data will stay as it doesn't dissapear over time.

Magnetic storage

Reliable, lots of storage at a low cost, can be internal or external.

Hard drive, normally in the computer itself, most of them have one.

Optical storage

Lots of storage at low costs, small and easy to distribute, they are robust and are normally read only,

Includes CD's and DVD's.

http://www.amazon.co.uk/TDK-CD-R80CBA10-B-CD-R-80min-Spindle/dp/B000A33TD2/ref=sr_1_2?ie=UTF8&qid=1382346135&sr=8-2&keywords=blank+cds

10cds with 700mb each for under £3 or equivalent of 30p each

Solid state

Includes stuff like USB, can be more expensive than other storages, flash memory, fast access times.

Include USB's or memory sticks.

This one costs £20 with 16GB memory space.

http://www.amazon.co.uk/Kingston-Technology-16GB-DataTraveler-DT101G2/dp/B003MWJKVI/ref=sr_1_1?ie=UTF8&qid=1382346591&sr=8-1&keywords=USB

first lesson

What is a computer system?

A computer system is a group of parts that work together to achieve the same goal.
All computer systems have one or more inputs, processes and one or more outputs.

Reliability 

Reliability is where it won't make and error and will always achieve the goal it was intended, so in a game, you gun will always fire in front of you when you fire.

Reliability is important because we heavily rely on computer systems, if a bank one glitches up then you might be left having no money/ a boat navigation system glitches you could crash into rocks / go opposite direction to where you want to go.

Even in the most reliable systems, like space craft, the system could still glitch, that is why there is no such thing as a 100 percent reliable system.

Input, process and output

Input- the information given to the system for example: you pressed left key

process- information is processed using programming and sometimes using information from the
program you are in.

Output- some kind of effect happens, say the gun fires at the zombie

Embedded system

An embedded system is a system designed to carry out a specific set of functions, and is inside the product, for example, it tells the washing machine will always have to clean the clothes depending on what type and how many, whereas a phone has to be flexible so it can react to new functions so it can make a person in this app move forwards when you press the forward key.

Regulations

Regulation exist to protect your information, to protect you from having your identity stolen, to stop people spending all your money. THE DATA PROTECTION ACT says: that your data must be up to date; be kept securely (especially if it goes to another country); be kept only for the time that is needed; be used for a particular lawful reason and be accurate.

several other Acts have been made to keep up with the ever changing technology and the regulations they need. The Computer Misuse Act was made to stop people hacking/ using someone's computer or material without permission or giving it a virus.

Also, some Acts like the copyright one, were made originally for a different purpose but include computers now. Under this Act, you cant copy and sell other people's copyrighted stuff, without their permission.