3. Data types and data structures

Data types
1. Numeric
  1. Advantages
    1. Calculations can be done
    2. Program can alter format
  2. two types
    1. Integer- whole numbers
    2. readl/double/float- decimal numbers
2. Boolean- only has two options- yes or no
  1. Advantages
    1. validated- less prone to errors
    2. easy to understand
    3. les storage space
  2. Disadvantages
    1. limited options
3. text
  1. two types
    1. String- texts or numbers that are stored in the ASCII code
    2. character- a string with 1 data size
  2. advantages
    1. can store anything
  3. disadvantages
    1. can't do calculations
Arrays
1. A data structure (group of data) of the same data type grouped under one identifier. All the data stayed contiguously in computer memory
2. Dimensions
  1. 1D- list of data
    1. Advanatges
      1. Easy to implement
    2. Disadvantages
      1. limited space
      2. same data type
  2. 2D- stores in a grid
    1. Advanatges
      1. good for games
      2. Simple to program
    2. Disadvantages
      1. limited in size
      2. same data type
  3. can have up to 32D but most people go up to about 3D
3. declaring an array
  1. initialise (give a name)- easy to access
  2. size of the array- locations of the memory will be reserved
  3. dimensions- allow position to have meaning
  4. Data type- allow correct data to be stored
Record Format
1. file- large quantity of data (multiple records
  1. To write:
  2. To read:
2. Record- info. on one particular thing (multiple fields)
3. field- one type of information
4. Key field- unique field- used as an identifier
5. fixed length- each record has a certain assigned amount of space
  1. quicker to search
  2. easier for the computer to store things
Files
1. file access
  1. Serial- stored in the order it arrives, To add- it just adds on, To delete- copy files to a separate tape leaving the one that needs to be deleted.
    1. Advantage- quick to store
    2. Disadvantage- inefficient to locate
  2. Sequential- puts sorted order depending a key field, To add- copy files to a separate tape leaving the one that needs to be deleted. To delete- same as above just delete unwanted files
    1. Advantage- search time is quicker
    2. Disadvantage- longer to write
  3. Random- has a space and the data is stored anywhere depending on the answer got by a hash calculation done on the key field, To delete- say that it is invalid and then overwrite it.
    1. Advantage- quick to read and write
    2. Disadvantage- inefficient when there is a large amount of data
  4. Direct- finds data instantly by using its length
    1. Advantage-quick to search
    2. Disadvantage-only works with fixed length records
  5. Index sequential-like sequential but has an index
    1. Advantages and disadvantages same as sequential but more quicker/ longer
2. files: store, retrieve and search,
  1. 1. define the stream (computers can know which stream using as a multiple streams are being used) 2. use the stream (read/write) 3. close the stream
  2. end of file character- used to show where the end of the file is. allows location of files much easier.
3. estimate file sizes
  1. 1. consider the data types for each field and then the amount of space required for each type 2. record size- add up each individual field size 3. file size- multiply previous to the number of files 4.files have extra info.- add 10% on 5.ensure that it is in correct units
4. programing

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3. Data types and data structures

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