Programming Techniques

Programming Techniques

1. Variables, Constants, Inputs and Outputs

   • Variables
     • A named memory location where information is stored - named using an identifier
     • Identifier - variable name - should be descriptive
   • Constant
     • Identifier that contain values that cannot change
     • Maybe declared with CONST in pseudocode
   • Input
     • Allows data to be input can be assigned to variables
   • Output
     • Displays information to the user
   • Assignment
     • Used to assign values to constants or variables e.g. pi = 3.14

2. Operators

   • +, -, *, /
   • MOD
     • Remainder from division for example 13 MOD 5 = 3
   • DIV
     • Integer Division 13 DIV 5 = 2
   • ^
     • Exponent - 4^2 = 16
   • Comparison
     • == Equal to
     • != Not equal to (sometimes shown as <>)
     • < Less than
     • <= Less than or equal to
     • > Greater than
     • >= Greater than or equal to
   • Boolean
     • AND
     • OR
     • NOT

3. String Operations

   • Uppercase - string.upper
   • Lowercase - string.lower
   • String length - string.length

4. SEQUENCING

   • Computer executes every instruction line by line

5. SELECTION

   • IF, ELSEIF, ELSE
     • Used to execute different code based on conditions
     • Can be nested

6. ITERATION

   • WHILE, FOR and REPEAT UNTIL Loops
     • For repetitive tasks
       • Nested iteration used when working through 2D arrays

7. File Handling

   • Used for persistence storage of data
   • 1. Open File
   • 2. Read line(s) into variable
   • 3. Close File
   • Read, Write and Append

8. Record Structures

   • Used to store fields with different data types

9. SQL - Structured Query Language

   • Used to read, manipulate data in a database
   • SELECT * from PUPILS - will select all records / fields from the PUPILS table
   • SELECT (Column1, Column2) from TABLE where Column1 = "xxx" and Column2 = "yyy" ORDERBY Column2

10. Arrays

    • Implemented as lists in Python
      • Use single index in 1-dimensional array e.g. string[0]
      • Use two values in a 2-dimensional array e.g. string[1,3]

11. SUBPROGRAMS

    • Save time and simplify code
    • Procedures - stored under one name - do not return value
    • Functions - stored under one name - DO return a value