Section 5 - Programming

Section 5 - Programming

1. Strings

   • String Manipulators
     • x.upper
       • Changes all characters in string x to upper case
     • x.lower
       • Changes all characters in string x to lower case
     • x.length
       • Returns the number of characters in string x
     • x[i]
       • Extracts the character in position i from string x
     • x.subString(a,b)
       • Extracts a string starting at position a with length b from string x

2. Arrays

   • Arrays are used to store multiple data values
     • An array is a data structore that can store a collection of data values all under one name
     • Each piece of data in an array is called an element
       • Each element can be accessed using its position or index in the array
     • Arrays are most helpful when you have lots of related data that you want to store and it doesn't make sense to use separate variables
     • Some languages require you to declare arrays before they are used
   • One-dimensional arrays are like lists
     • Creating arrays
       • ARRAY array_name[x]
         • array_name[0] = "Hello"
           • This sets array_name's position 0 to "Hello"
         • array_name would be the name you choose for the array
         • x being the number of data pieces you need
     • Retrieving elements
       • print(array_name[0])
         • This will print what's in position 0 of the array_name array
     • Changing Elements
       • array_name[0] = "Bonjour"
         • This will then change the data in position 0 to "Bonjour
   • Two-dimensional arrays are like lists of lists
     • The position of an element is written as [a, b] or [a][b]
       • a represents the position of the one-dimensional list that the element is in
       • b represents its position within that one-dimensional list
     • Example
       • trees = [["oak", "ash"], ["beech", "cedar"], ["pine", "elm"]]

3. File Handling

   • Must start by opening the external file
     • Example
       • newFile = openRead("newFile.txt")
         • newFile = openWrite("newFile.txt")
   • Once the file has been opened you can continue to write to it until you close it
     • newFile.close()

4. Storing Data

   • Databases
     • Databases store data in tables
       • The columns of these tables are called fields
       • The rows are called records
     • A field is used to store a category
       • A record will use the fields to store details about a specific item
     • All data values in the same field must be the same data type
       • But... data values in the same record can have different data types
     • Most Databases use SQL (Structured Query Language)
       • Create and Update tables
         • CREATE TABLE
           • This SQL statement will create a table with as many fields as you want
         • Once a table has been created you can add records to it
           • INSERT INTO
             • This SQL statement will insert the data into the table
         • To update a table you shall use the Update
           • UPDATE-SET-WHERE

5. Sub Programs

   • Procedures and Functions will help to avoid repetition of code
     • Procedures are a set of instructions in which are stored under one name
       • Means if you want the program to do these instructions you just call the name
     • Functions are similar, however they always return a value
     • They can give your program more structure and readability while cutting the amount of code down
     • Sometimes you'll encounter parameters and arguments
       • Parameters
         • Special values used to pass values into a sub program, for each parameter you have to specify a name, data type and default value
       • Arguments
         • The actual values that the parameters take when the sub program is called
   • Variables can be local or global
     • Every variable has a scope
       • Each scope will tell you which parts of the program the variable can be used within
     • Local
       • Can only be used within the structure they're declared in
     • Global
       • Can be used any time after their declaration