2.2 Programming V2

Subroutines
1. Procedures
  1. Are defined and called by their names
  2. They do not return their values
2. Functions
  1. Are called by assigning their return value to something
  2. They always return a single value
3. Defines a large amount of coding into one value
  1. Useful to reuse code faster
  2. Good so work can be split between programmers
    1. Variables
      1. Values change throughout the program
    2. Constants
      1. Stays fixed throughout the program
    3. Used within subroutines
      1. Both are used to store data whilst the program is running
SQL (Standard Query Language)
1. Programming language used to work with databases
2. Can be run from a special window in a database package
3. SQL Keywords
  1. SELECT
    1. The variable you want to find
  2. FROM
    1. From which database
      1. e.g. To find a SongTitle more than 3 mins long
        SELECT SongTitle FROM Songs WHERE Length > 3
  3. WHERE
    1. Different columns
Iteration
1. The repetition of a process
2. For Counter (Counter-controlled)
  1. Loops for a specific number of times, depending on the counter number
3. While Loop (Condition-controlled)
  1. Better for user interfaces
  2. Loops until the condition is met/changes
Operators
1. Arithmetic Operators
  1. / - Division
  2. * - Multiplication
  3. + - Addition
  4. - - Subtraction
  5. MOD - Modulus (Remainder) e.g.12 MOD 5 = 2
  6. DIV - Ouotient e.g. 17 DIV 5 = 3
  7. ^ - Exponentiation (To the power of)
2. Represents the operations that are performed on the data
3. String Operators (String Manipulation)
  1. .length - Number of characters in a string (including spaces)
  2. .lower - lowercase
  3. .upper - UPPERCASE
  4. .substring (x,y) - Part of a string
4. Comparison Operators
  1. != - Not equal to
  2. == - Equal to
  3. < - Less than
  4. > - Greater than
  5. <= - Less than or equal to
  6. >= - Greater than or equal to
5. Logical Operators (Only used in Booleans)
  1. AND - Two conditions must be met for the statement to be true
  2. OR - At least one condition must be met for the statement to be true
  3. NOT - Inverts the results e.g. NOT(A and B) will only be false when both A and B are true`
Arrays
1. Begins with 0
2. Usually have fixed sizes and occupy a fixed (static) amount of memory
3. A table of organised data
4. Advantages
  1. Non-sequential nature - can jump between non-neighbouring elements instantly without having to browse through the whole array
  2. Good for ease of iterating through an array - allows us to manipulate multiple times of data with very few lines of code,replacing may separate variables
5. 2D Arrays
  1. Has rows and columns
  2. Each individual rows/columns/index hold different series of data
6. 1D Array
  1. Only holds one series of data (like a pie chart)
Selection
1. Allows a computer to "think" - make decisions
2. Changes the flow of a program, depending on a set of conditions, it is used for validation, calculation and making sense of a user's choices
  1. e.g. IF, ELIF, ELSE, SELECT CASE statements
3. Nested Selection
  1. Sometimes, we can only evaluate a condition if some pre-condition is met. We would need two selection statements, one inside the other
  2. The "outside" selection is the pre-condition, while the "inside" selection is the conditon
  3. e.g. IF....... IF
    1. IF Statement within an IF Statement
Sequencing
1. Allows a programmer to solve complex tasks through a number of simple instructions (sequence/algorithm)
2. Advantages
  1. Each line follows the next
  2. Create simple programs very quickly
  3. Easy to follow for a small program
  4. Fundamental priniciple of a program
  5. Starts at the top, finishes at the bottom
3. Disdavantages
  1. Not at all efficient
  2. Extremely hard to maintain
  3. Becomes very difficult to follow with large problems

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	Creado por 2402 2003 hace más de 5 años