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Data (Binary (General (Bit:- the smallest unit of data in a computer, and…
Data
Binary
Adding:Overflow errors occur when a calculation produces a result that is greater than the computer can deal with. A 9th bit is required. 1+0= 1, 0+0=0, 1+1=1,0
Denary
Converting to Binary- You can convert denary numbers with values from 0 to 255 into 8-bit binary numbers. Write out the values of 2^n from righto left. Starting at the left, if the denary number I greater then place a 1 in the column. subtract the value of 2^n from your original answer to get your next denary value and continue along the table.
Converting from Binary- Above the given binary code, write out 2^n from right to left. for every column that has a 1 in it, count the denary value. Add all these digits together to get you final denary total.
Logic Shifts: Used when multiplying or dividing binary number by powers of 2.
When multiplying binary numbers, you move the binary digits the desired amount of places to the left depending on the power.
When dividing binary numbers, you move the binary digits the desired amount of places to the right depending on the power
Hexadecimal
Binary to hex. Split the 8-bit byte into two 4-bit nibbles. Convert the bits in each nibble into denary numbers using the place values. Add these together to give the hexadecimal
Hex to Binary- Convert each hexadecimal into binary, convert into a nibble then combine to give 8-bit denary.
ASCII:"American standard code for information interchange". Characters like letters a to z and A to Z and the digits 0 to 9 are each given a standard code which is the same on all computer systems.
Signed Intergers
Two's Complement:Write out the number in binary. Invert the digits, and add one to the result. Effective when adding or subtracting. Used to represent negative numbers
Sign and Magnitude:A way of representing negative numbers.Bit at the far left of the bit pattern (sign) indicates whether the number is positive or negative. The rest of the bits in the pattern store the size of the number (magnitude). 0 indicates a positive number and a 1 indicates a negative number.
General
Bit:- the smallest unit of data in a computer, and contains a single binary value, 0 or 1.
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Data Storage
Compression
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Advantages:-Can be transferred to other systems more quickly. -Takes up less disk space than an uncompressed version
Lossy-Makes file smaller by getting rid of bits and hoping you won’t notice. If something is similar, they are made to be the same. Any bits that are lost cannot be recovered.
Lossless- File is reduced without losing any quality; original file can be restored. Won't make a file as small as a lossy method
RLE-.Run-length encoding- reduces file size by checking for redundancy, reduces the size of a repeating string of items.
Converting between units- Makes the file smaller by getting rid of bits and hoping you won’t notice. If something is similar, they are made to be the same. Any bits that are lost cannot be recovered.
Database
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Tables- In a database, each entity is represented as a table with its attributes as the columns so that the cells can be used to store data in a structured and organised manner.
Structured/unstructured
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Unstructured- not organised and is stored in things such as emails, word documents, images and uploads. Can't be searched for easily
Entities-entity is a thing which is recognised as being capable of an independent existence and which can be uniquely identified and about which data can be stored. Usually a physical object or concept.
Identifying the entities are independent objects which data can be stored about
Attributes- the set of properties used to describe instances of the entity. They are items of data that can be stored about an entity.
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Encryption
Caesar Cipher- shifting letters of the alphabet to the left or right a set number of places. Number of places shifted is called the key.
How it works:- carried out using an algorithm called a cipher which often uses keys. One key is used to encrypt data, the other to decrypt it so that it can be understood
Sound and Images
Sounds
Digital Use snapshots of the sound at regular fixed intervals and then play them back one after the other. These snapshots are called "Samples".
Analogue- Can be represented in digital form as streams of 1s and 0s. Sound is caused by vibrations travelling through a medium such as air, water or a metal
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Images
Pixels- small points of colour. Each has its own individual colour, the greater number of pixels, the greater detail in picture.
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File size - depends on image size and colour depth. The better the image quality, the larger the file size
width x height x colour depth