Intro to Programming and Scratch

In our first meeting we discussed a little history of computer programming and introduced Scratch:

Program: A set of computer code written to execute some useful feature, application, etc.

Programming Languages: A defined set of instructions that can be used to tell a computer what to do. Programmers write code by determining which instructions to put together in which order

  • Machine Language: Set of instructions composed of numerical “bits”, only ones or zeroes. A computer understands this natively, each processor family has its own set of instructions. They would look something like this: 00100001 11101011 01010101
  • Assembly Language: Also called Assembler Language. Low-level programming language; uses abbreviated words (Mnemonics), e.g. MOV, to represent instructions to the computer. Assembly instructions are translated by the Assembler into machine language
  • High Level Language: Each language has its own syntax, keywords, functions, etc. Uses natural language, such as English. Abstraction refers to the way in which these languages abstract details of what the machine needs to be told, so that a simple function call can actually represent many instructions behind the scenes

Compiler: Translates high-level languages to code that can be executed by the computer.  There are specific compilers for each language (Java, C#, COBOL, etc.). Compilers do a lot of the complex work behind the scenes of a program. Note: Some languages are Interpreted rather than Compiled; that is, the code is executed as it is being read

Debug: Figure out what is wrong with a computer program and fix it.  Specialized debugging tools are often part of a development environment and allow programmers to step through the code one line or block at a time and inspect the immediate results

IDE: Integrated Development Environment. An application that provides an interface and tools for programmers to create, execute, and debug code. Visual Studio, Scratch, Eclipse, NetBeans are all examples of powerful IDE’s

Loop: a code control structure that causes code to be repeated a specified number of times or based on a condition (while or until some condition is true); a loop that runs “forever” is called an Endless Loop

Event: a trigger that the program is “listening” for; code blocks can be “hooked” to events so they will execute when the event occurs. In Scratch, an event commonly used at the top of a script is the clicking of the green flag to start

Script: A set of computer instructions connected to run together to do something. In Scratch, we create scripts by connecting blocks

Scratch: a visual programming language developed at MIT enabling coders to drag and drop blocks of code to form scripts to control sprites on a “stage”

  • Sprite: an image, often like a cartoon character, to which scripts, costumes, and sounds can be attached to control its appearance, movement, and behavior
  • Backdrop: the scenery behind the Sprites within a Scratch project
  • Stage: the area on which the backdrops and sprites are drawn and move
  • X/Y Coordinates: define a point on the stage. X represents the point on the horizontal axis from -240 on the far left to +240 on the far right. Y represents the point on the vertical axis from +180 at the top to -180 at the bottom. The center of the stage is at 0,0.
  • Block: In Scratch, a block is a unit of code that can be added to a script to build a working program
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