Topic 3 - Data Flashcards
What is Binary?
A Base-2 numbering system. (only has 2 digits - 0 and 1)
What is Denary?
A Base-10 numbering system (from 0 - 9)
What is a nibble (in bits)?
4 bits.
When there is an extra digit in a binary calculation, what is this called?
Overflow.
What does ‘1’ represent in Sign and Magnitude?
Negative
What does ‘0’ represent in Sign and Magnitude?
Positive
What is a Hexadecimal?
A Base-16 numbering system (16 digits. It shares 0-9 with denary then uses letters A-F)
Why are Hexadecimals used?
They simplify long streams of bits
What are Real Numbers?
Numbers with an integer part and a fractional part.
What is the scientific notation of representing floating point binary?
Mantissa x Base^Exponent
What is the name of the subset that ASCII is in?
Unicode
Why is Unicode better than ASCII?
It can represent a wider range of characters (e.g. from other languages such as: é)
What is a Bitmap?
An image stored as an array of individual pixels.
What is a Pixel?
An individual picture element.
What is Colour Depth?
The number of bits allocated to represent each colour
What is ‘Resolution’ of an image?
The detail it holds within an image.
How can ‘Resolution’ be displayed as?
width x height OR the number of ‘Pixels Per Inch (PPI) ‘
What are Analogue Signals?
They’re continuous, they don’t have defined ranges, and are represented often by waves.
What are Digital Signals?
They form discrete values (they fall within a defined range and can only take certain values).
What are three everyday examples of Analogue Signals?
Sound, temperature and light intesity
What is Sampling?
The process of recording an analogue signal at regular intervals.
What is ‘Sampling Frequency’ ?
The average number of samples obtained per second. Measured in Hertz (Hz)
What is Quantisation?
The process of approximating the analogue values to predetermined discrete levels.
What is a bit?
1 or 0
What is a byte?
8 bits / 2 nibbles
What is a Kilobyte (in bytes) ?
1024 bytes (2^10 bytes)
What is a Megabyte in KB?
1024 KB (2^20 bytes)
What is a Gigabyte in MB?
1024 MB (2^30 bytes)
What is a Terabyte in GB?
1024 GB (2^40 bytes)
What is the formula of Transfer Rate?
Transfer rate = b/s
What is data compression?
The reduction of file size whilst retaining the underlying information.
What is Lossy Compression?
Some of the original data is lost
What are two examples of lossy algorithms?
MP3 (audio) and JPEG (images)
What is Lossless Compression?
Compresses the data without losing any data
What is an example of Lossless Compression?
Run-length encoding (RLE)
How does RLE work?
It collects all the like terms together (e.g. y y y = 3y)
What is encryption?
The process of making data secret to that only authorized viewers can decrypt and read the data, and third parties cannot.
What are the 5 steps of encryption?
- Message written in plaintext
- Message is encrypted into ciphertext
- Message is sent
- Message is received
- Message is decrypted back into plaintext
Why is encryption used (2 reasons) ?
- To protect data
2. To verify the sender
How does a Caesar Cipher algorithm work?
Letters in the alphabet are shifted depending on the shift key
What are the two arrangements of data?
Structured and unstructured
What are the differences between structured and unstructured data?
Structured - arranged in an organised and defined way.
Unstructured - cannot be easily mapped by a computer in predefined fields.
What is a Database?
A collection of information that is organised so that it can be easily accessed, managed and updated.
What is a Relational database?
Consists of tables linked together with each other by key fields.
What is a table?
A two-dimensional representation of data that is stored in rows and columns.
What is a Field?
Single piece of data about an entity
What is a Record?
The group of fields about a specific entity (a row)
What is a Report?
A presentation of data from the database
What are Queries?
Requests of data stored in the database
What is an Entity?
An object/person/thing about which data is stored.
What is an Entity Relationship?
A model used to identify entities and how they relate when designing a database.
What is a relationship?
Link between entities.
What is a primary key?
A field that uniquely identifies a record.
What is a Composite Key?
A combination of fields in a table used to uniquely identify a record.
What is a Foreign Key?
A field in one table that is a primary key in another table.
What is Structured Query Language (SQL) ?
A specialised programming language for creating database structures and managing data in them.
What does INSERT do?
Enters a record into the table and stores the value in the specified column.
How does INSERT work?
INSERT INTO TableName (Field1, Field2…)
VALUES (“abc123”, “abc123”)
How do you create a table?
CREATE TABLE TableName
ColumnName datatype, …
How do you UPDATE something?
UPDATE TableName
SET (ColumnName = Value, …)
WHERE ;
How do you DELETE something?
DELETE * FROM TableName; (deletes everything)
DELETE FROM Student
WHERE Student
How do you SELECT something?
SELECT (ColumnName)
FROM TableName
[WHERE ]
[ORDER BY (ColumnName,…)];
