Computer Science Principles Unit 1 Notes

Computer Science Principles Unit 1 Notes 1.1  Debugging- checking and fixing error in one’s code.  Iteration cycle: Ideaalgorithm write codeexecute (run) codedebugmaintain.  Always develop and research an idea before executing/programming it.  Sequencing- everything happens in a linear order; one after another. (ex: Scratch, Robot)  Selection- uses “if…then” logic to determine the next step of the sequence to follow.  Iteration- uses repetition until a certain condition is met  Good algorithms are specific and precise. (ex: recipes)  Key features of algorithms: good format, imperative statements (command that clearly 1.2 notes which operation should be performed), and descriptive qualifiers (distinctions that need to be made, ex: left shoe, right shoe)  Algorithms can be expressed differently: flow charts, pseudo code, mathematical notation, etc. 1.3  natural language: a complex, but structured language, both written and spoken, that has evolved naturally in humans through use, repetition, and adaptation.  Binary- machine code that is a direct, low-level translation from the high-level source code, and is a pattern of 0s and 1s.  Abstraction- the process of removing or suppressing details to create a manageable level of complexity.  Artificial language- a limited size language, usually developed by a small group for specific purposes. Usually much simpler and structured.  Ambiguity- uncertainty or being open to more than one interpretation.  Visual programming language- a programming language that lets users drag and drop icons into organized blocks of code to create programs rather than typing text.  High-level language- a programming language that is easier for humans to read, write, and parse. Guaranteed to be unambiguous.  Low-level language- a programming language that has little or no abstraction and communicates closely to the hardware using machine language. Less natural for humans.  Compilation- the process of source code being translated into machine code.  A process uses input: a user-initiated instruction that is compiled into bionary code, 1.4 memory (RAM): memory storage space. The (CPU): processor that calculates all the information, and output: the physical display of the calculated information (sound, image, etc.)  Bit- Combination of the words binary and digit – a 1 or a 0.  Source code- programs written in high-level languages.  Machine code- machine-level instructions that are uniquely read by computer processors using 1s and 0s.  Compilation- the process of source code being translated into machine code.  Scratch can allow people to mix together sound, graphics and media  Scratch is a block-based programming language developed by MIT  Block-based is high-level. All about stacking blocks of code  Block-based focuses on logic rather than the syntax.  Scratch isn’t just for babies  Booleans- hexagon shaped blocks: ask a question and only answered true or false.  Oval blocks- give a value related to the sprite.  Processing- Instructing the computer to do some calculations. Processing can be used to 1.5 1.7 solve problems or create animations.  Output- Any data sent from a program to a device. This is usually observable by the person using the program. This data can take on many forms such as tactile, audio, visual, or text. A programs output is usually based on a program's input or prior state.  Input- Any data sent to a program to affect its behavior. In Scratch this is most commonly User Input through key presses and mouse clicks, but programs can sometimes take input from other programs. The input to a program typically affects the output of a program, for example in a game pressing the arrow keys will usually make a character move around the screen.  Behavior- The three concepts above combine to create the behavior of a program. The behavior of a program is how a program functions during execution and is often described by how a user interacts with it. A program should work for a variety of inputs and situations to create complex behavior.  State- a description of what the computer is doing or the values of variables at any given moment.  Attributes- a description of what the computer is doing or the values of variables at any given moment.  Process- the program code and current activity that is being executed in a computer program.  Position- the x and y coordinates on the stage in Scratch.  Sensing Blocks- light-blue colored Boolean blocks that are used to detect different factors or a project such as touching.  Placeholder- a variable for a particular value or attribute.  Variables are at the core of any program. They are used to store information to be 1.8 referenced and manipulated in a computer program. Consider that when you type information into a web form and send it, the information is stored in variables. These variables are later used in the program. Since the information will change depending on the person using the form, these variables are storing dynamic information.  Variables are containers with labels.  Types of variables: -Integer (int) -Character (char) -String: “ “ -Boolean (bool) -Array -floating-point number (float)  Set values: =, comparisons: ==  Variables are defined at the beginning of the program.  Variable- A variable is an abstraction inside a program that can hold a value  Placeholder- a variable for a particular value or attribute.  Integer- a whole number; a number that is not a fraction that is used in programs.  Character- a single letter, digit, or symbol that can be a type of variable.  String- a series of characters at any length. Can be a type of variable.  Boolean values- a variable to represent true or false.  Array- lists of other variables.  Floating point number- a number that may have digits after the decimal place. Can be a type of variable.  Declaring variables: creating variables in a programming language  Variables in computer programs are similar to ones in math because they are both 1.9 placeholders.  Importance of creating your own variables.