2.2 Programming Basics

2.2 Programming Basics

1. Data Types

   • Integer
     • int
     • Whole Numbers
   • Boolean
     • bool
     • Can only take two values such as TRUE or FALSE
   • Character
     • char
     • Single letter, number or symbol
   • String
     • string
     • Used to represent text, a collection of characters
   • Casting
     • Conversion between data types
     • int("1)
     • float(1)
     • bool(1)
     • str(True)
   • Real(float)
     • Decimal numbers
     • real

2. Basic Operators

   • + is Addition
   • - is Subtraction
   • Multiplication is *
   • Division is /
   • Exponentiation is ^
   • Quotient is DIV
   • Remainder (Modulus) is MOD or %
   • Comparison operators
     • == is equal to
       • <> or !+ is not equal to
         • < is less than
           • > is greater than
             • <= is less than or equal to
               • >= is greater than or equal to

3. Constants and Variables

   • Constants are assigned to a data value at a designated time that cannot change.
   • Variables can be changed, unlike constants

4. Strings

   • Strings are written inside quotation marks
     • x.upper will change all characters in string x to UPPER CASE
     • x.lower changes all characters in string x to LOWERCASE
     • x.length will return the number of characters in string x
     • x[i] will extract the character in position i from string x
     • x.subString(a,b) will extract a string starting at position a with length b from string x

5. Program Flow

   • IF statements
     • Checks if condition is true or false.
     • Nested IF statements
       • Allows you to check more conditions once you've established that the previous condition is true
       • Made by putting one IF statement inside another
   • IF-ELSEIF statements can also be used to check multiple conditions, however, nested IF statements can only check more conditions if the previous condition is false

6. SWITCH-CASE statements

   • Used to check if a variable has specific values
     • Used when you want a program to perfom different actions for different values of the same variable
     • Can only check value of one variable

7. FOR Loops

   • Will repeat the code inside them a fixed no. of times
   • The no. of times that the code is repeated depends on initial value, end value and step count

8. DO UNTIL LOOPS

   • Controlled by condition at the end of the loop
   • Continue until condition is true
   • Infinite loop is condition is never true

9. WHILE LOOPS

   • Controlled by condition st start of loop
   • Continues while condition is true
   • Never runs if code is initially false

10. DO WHILE LOOPS

    • Controlled by condition at end of loop
    • Continues while condition is true
    • Always runs code inside at least once
    • Infinite loop when condition is always true

11. Booleean operators

    • AND will only return true if two things are True
    • OR will only return true if one of the things are true
    • NOT will only return true if there is one thing that is a LIE

12. Arrays

    • A data structure used to store a collection of data all under one name
    • Useful for storing related data

13. FILE HANDLING

    • To open a file, you must open it and assign it to a variable
      • Program will start reading or writing from the beginning
        • When finished reading/writing, close it use close() or the file can remain locked and prevent others from editing it
    • Reading/Writing
      • writeLine() will write lines of text to a file and overwrite already existing text
      • readLine() will allow you read lines of text from a file
      • endOfFile() will allow you to signify when a program should stop reading a file.

14. Storing data

    • Record will store a collection of data values
      • Each item is called a FIELD
      • Each field gets a name and a data type
      • Fixed in length, so extra fields can't be added when created

15. Searching data

    • SELECT is followed by the names of the fields you want to find
      • FROM is followed by the name of the table that you want to search
        • WHERE is used to specify condition that a record must satisfy before being returned
          • ORDER BY sorts records into ascending or descending order

16. SUB PROGRAMS

    • Procedures are sets of instructions stored under one name
      • Functions always return a value
      • Parameters are sued to pass values into a sub program
        • Arguments are the actual values that the parameters take when the sub program is being called
          • SCOPE(tells you which parts of the program the variable can be used in)
            • Local variables can only be used within the structure
              • Scope only extends to sub program they are declared in
            • Global variables can be used any time after declaration