cs.md

Computer Science Concepts

• Programming
• Writing Code
• Get Information from Computers
• What can Computer's do
• Variables
• Manipulating Variables
• Conditional Statements
• Arrays

Programming

• Dictory definition: the process of preparing an instructional program for a device
• Layman's Terms: attempting to get a computer to complete a specific task without making mistakes
• Not-Intelligent (Computers)
  • Can only work based on our commands
  • FAR from competent, so we must give them EXACT instructions on how to do their task (Dumb)
  • Computer's are only only smart because we program them to be
• Language of Code
  • Computers only understand machine code
    • A series of 0's and 1's which interpreted by the computer
    • We need to convert our instructions from English to Binary in order for the computer to understand them
  • One Problem
    • It would be entirely unpractical to convert every programming instruction into binary by hand
• Programming Languages
  • Translate our instructions into machine code
  • Very useful for programmers
  • Serves as interpreters for converting languages into other languages
    • Faster than converting by hand
• High vs Low Level
  • Each language has an attribute known as power or level
    • Basically how similar it is to machine code
  • Low-level programming languages: Assembly or C
  • High-level programming languages: Java or Python
  • Lower the level -> More similar to machine code

Writing Code

• IDE's (Integrate Development Environments)
  • A place to write, run, debug code and converts it to machine code
  • IDE's are like any other program on our computer except used for the facilitation of code, e.g., (NetBeans, IntelliJ, Visual Studios)
  • Looks: Usually has central area for writing code, console, project hierarchy, preview screens, etc.
• IDE Functionality
  • Built-in Error-checking
  • Auto-fill for frequently used words
  • Project Hierarchy
• Learning Languages
  • Learning a computer language can be very similar to learning a real language
  • All programming languages have a set of rules to follow when writing code in that language, just like in real languages
    • In computer science it is called syntax
  • Similar to grammar in real life languages
• Syntax
  • Rules we must follow if we want our program to run correctly
    • How we type out certain functions
    • What to put at the end of each line of code
    • How to set up certain functions
  • Syntax for each programming languages are unique
  • Breaking programming rules will result in an error

Get Information from Computers

• The Console
  • Programmers keep track of their progress by looking at the console
    • A text interface within the computer that programmers can use for a variety of purpose
• How to Use the Console
  • Main use of the console is to output text from the program using code
    • Print statement prints text to the console for the programmers viewing pleasure
• Using the print Statement
  • Simply instruct the console to print, and include it inside the parenthesis
    • Using python, e.g., `print ("Hello Word")
  • Print statement is also usef for viewing and interpreting the computer's output from a program
• A Background Tool
  • The console is mainly a Developer Tool
    • Not usually meant to be used and interacted with by the end user except in very abstract cases
      • Text-based games/simple programs
  • Tends to be hidden away behind the scenes
  • Don't try and implement the console in the final product

What can Computer's do

• Math
  • Knows how to do simple arithmetic
    • Addition, Subtraction, Multiplication, and Division
  • Print the result of any math operation
  • May seem useless, but comes in handy extremely often
• Modulus %
  • Most programming languages has an additional operator known as modulus (%)
  • Allows us to get the remainder of divisional operation
  • Useful when determining if a number is even or odd
    • if a number modulo 2 is 0 -> The number is even
    • if a number modulo 2 is 1 -> The number is odd
• Strings
  • Another way of saying text
  • Anything enclosed by quotation marks
• String and Number Dilemma
  • "4" is treated as a STRING
  • 4 is treated as a INTEGER

Variables

• What is it
  • Something that can store information
    • Can be referenced and manipulated
• Basics
  • Each variable has a type, a name, and a piece of information stored inside of it
    • Name is simply a name for the variable
• Types
  • Primitive type variables
    • Integers, booleans, floats, doubles, Strings, and Chars
• Integers
  • A variable that can store an integer value, e.g., -2, 147, 648
  • CAN'T and WILL NOT hold any decimal values
• Booleans
  • Can ONLY store and hold a value of either true or false
• Floats and Doubles
  • Both are types of floating point data types
    • Can store numbers with decimal places
  • Float Variables can store up to 32 bits of information
  • Double Variables can store up to 64 bits of information
• Strings
  • Useful for displaying text and storing input information
    • Information the user puts into our program
  • Also useful for outputting information in a readable format for the user
• Chars
  • Each hold one character
  • Useful when a programmer wants to read one button press of one character in a string without using a String variable, e.g., Game controlled by keyboard
  • Tip: We can store char's in a String variable, but not String longer than 1 character in a char variable
• Usefulness
  • track of things, i.e., user's name or score
    • store this information in a variable and then reference, add to, or modify it
  • Other important uses for variables
    • Taking input from the user
    • Making our program have variability
      • Have it change based on certain factors
    • Manipulating variables is necessary for many tasks in programming

Manipulating Variables

• What happens when we define a variable
  • Create a space in memory that stores variable name and its content, e.g., int x = 10;
• Blank Variable
  • Reasons to do this:
    • We want to store the information in the variable down the road
    • We are going to use it to store information given to us by the user
  • Trying to reference a blank variable will result in a NULLPointerException (which we want to avoid)
• Dual Pointed Variables
  • 2 Variable names that points to the same contents which is String "NullPointerException"
  • We do this to save space in our code for the things we know that will have the same value
• Updating Variables
  • Game character has different stats
    • Life = 100 -> 85
    • Potion = 80 -> 64
    • Armor = 20 -> 16
• Fate of Variables
  • After code has run its course, variables are deleted in memory
• Other Ways of Manipulating Variables
  • Integer, Float, and double variables can be
    • Added
    • Subtracted
    • Multiplied
    • Divided
    • Modulused
  • String variables
    • Added
  • Char's and Boolean's can't be operated on
• Naming Convention
  • One big rule: MUST be one continuous String
  • camelCase, e.g., firstName

Conditional Statements

• Conditional Statements makes our code do different things
• If Statement
  • If True do this, otherwise do something else
  • Most programming languages uses parenthesis ()
    • Inside parenthesis will be evaluated as either true or false
  • If the statement is true, whatever is enclosed inside a set of curly braces directly after the if statement will run
• Booleans
  • Each condition is evaluated as a boolean: True or False
• Else-If Statement
  • Will only be evaluated if the preceding if (or else-if) statement is false
• Else Statement
  • Will only run if all previous cases are not true
• Running through If-Else Statements
  • Check initial statement
    • If true, run that segment of code and move on with the program
  • If false
    • Move to any else if statements and evaluate those conditional Statements
  • If any of them are not true
    • Run that segment of code in else statement and move on
• Switch Statement
  • An easily collapsible way to write many if-else statements
    • Input a variable, then determine which "Cases" that variable could be
  • Uses colon (:) instead of curly braces
  • Each switch statement alseo includes a "default" case (Else statement)
• Usefulness of Conditional Statements
  • Adds variability to programming
    • Program runs differently based on user input
  • If a user does something, we want to be able to adapt accordingly
  • Without, a program would run the same way every time

Arrays

• Where do Variables Fail
  • Can only store singular bits of information
  • Not able to hold more than one piece of data
• Arrays
  • List of something
    • Integers
    • Strings
    • Even other array's
  • All information in an array is related
  • Like columns in Google Sheets
• Referencing Arrays
  • Most important thing about arrays is how we reference each element inside of it
    • In programming we use Indexes
      • Indexing begins at 0
  • Referencing the 10th element using 10 instead of 9
    • Would result in an "Out of Bounds" error
• Creating Arrays
  • Populate First
    • Insert the elements in the array immediately
  • Populate Later
    • Create an array with specific size, but choose to add elements later
• Array Sizes
  • When we create array their size are FINAL
    • Cannot be increased or decreased in size through conventional methods
    • This is what allows us to easily access their indexes
• Array Types
  • When initializing an array, we must determine its type then and there
    • e.g., String array, Integer Array, Double Array, etc.
  • They all have to be the same type
• 2D Arrays
  • Putting an array inside an array is known as a 2-Dimensional Array
    • Similar to Matrices in math/physics classes
  • Each index in the array is actually another array with it's own set of indexes
• Indexing 2D Arrays
  • To index 2D arrays we use 2 numbers
    • First number for row
    • Second number for column