1.3 Exchanging data Flashcards
Why do we need to reduce the size of files
Data is sent more quickly
Less bandwidth is used
Buffering less likely to occur
Less storage is required
What are the two types of compression
lossy and lossless
What is lossless compression?
File size reduced without losing any original data
What is lossy compression?
Unneeded data permanently removed to lower file size. This data that is removed will be non noticable such as certain sound frequencies.
How does lossless compression work?
Records patterns in the data instead of the data instead to prevent recording redundant data
when should lossless compression be used
when no data can be lost for example a word document
examples of lossy compression
JPEG, MP3, MPEG
examples of lossless compression
ZIP
PNG
GIF
What are the two types of lossless compression
Run length encoding
Dictionary encoding
What is run length encoding?
Compression where conexcutive identical pieces of data are stored as one piece of data and a number representing length
What is dictionary compression
Spots regularly occuring data and stores it in a dictionary
How does dictionary compression reduce size
Repeated phrases are only stored once and are referenced with an identifier
What is encryption
The process of encoding a message so that it can be read only by the sender and intended recipient.
What is symmetric encryption?
An encryption method in which the same key is used to encrypt and decrypt a message
What is asymmetric encryption?
An encryption method in which two keys (one private, one public) are used to encrypt and decrypt a message. Such that someone with the public key can only encrypt and someone witht he private key can only decrpyt.
What is a one time pad
A one time key generated via random methods used for symmetric encryption
What is hashing
A one-way encryption an algorithm but no key
What are the uses of hashing
Storing passwords securly
Uniquely identify a file
What is a flat file database?
A database that consists of information on a single entity
What is an entity
A category of object, person, event or thing of interest about which data needs to be recorded
ther names for entities
Record, tuple
What is a relational database
Database that stores data points that are related to each other
What is a primary key
A field (or group of fields) that uniquely identifies a given entity in a table
What is a secondary key
Another field that can be used to identify an entity in a table