Scratch (programming language)

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Scratch Logo.svg Scratchcat.svg
Paradigm event-driven, imperative
Designed by Mitchel Resnick
Developer MIT Media Lab Lifelong Kindergarten Group
Appeared in 2006; 9 years ago (2006)
2.0 / May 9, 2013; 22 months ago (2013-05-09)
Implementation language
Squeak, ActionScript (Scratch 2.0)
License GPLv2 and Scratch Source Code License
.sb, .sprite (Scratch 1.4 and below) .sb2, .sprite2 (Scratch 2.0)

Scratch is a free desktop and online multimedia authoring tool that can be used by students, scholars, teachers, and parents to easily create games and provide a stepping stone to the more advanced world of computer programming or even be used for a range of educational and entertainment constructivist purposes from math and science projects, including simulations and visualizations of experiments, recording lectures with animated presentations, to social sciences animated stories, and interactive art and music. Viewing the existing projects available on the Scratch website, or modifying and testing any modification without saving it requires no online registration.

Scratch allows users to use event driven programming with multiple active objects called "sprites". Sprites can be drawn — as either vector or bitmap graphics — from scratch in a simple editor that is part of the Scratch, or can be imported from external sources, including webcam.

Scratch 2 is currently available online and as an application for Windows, Mac OS X and Linux.[1][2] The source code of Scratch 1.x is made available under GPLv2 license and Scratch Source Code License.[3]

A spinoff of the Scratch programming language is also used in the game creation tool Stencyl.

Origin of name[edit]

The name was derived from the turntablism's technique of scratching[4] (i.e. mixing sounds), relating the ease of mixing sounds to the ease of mixing projects made with Scratch.


The first web-based Scratch in 2006

The MIT Media Lab's Lifelong Kindergarten group, led by Mitchel Resnick, and its Montreal-based consulting company Playful Invention Company, co-funded by the latter with Brian Silverman and Paula Bonta, together developed the first desktop-only version of Scratch in 2003. Since 2007, projects could be shared online with other users and the shared projects could be "remixed" (i.e. saved with changes) by other users.

Since the introduction of Scratch version 2.0, custom blocks can be defined by a user within a project.[5]

User interface[edit]

Scratch 2.0 development environment and its different areas at startup

From left to right, in the upper left area of the screen there is a "stage area", featuring the results (i.e. animations, turtle graphics, etc., everything either in small or normal size, full-screen also available) and all sprites thumbnails listed in the bottom area.

With a sprite thumbnail selected in the bottom-left area of the screen, blocks of commands can be applied to it by dragging them from the Blocks Palette onto the right area of the screen, containing all the scripts associated with the selected sprite. Under the Scripts tab, all available blocks are listed and categorized as the Motion, Looks, Sound, Pen, Data, Events, Control, Sensing, Operators, and More blocks as shown in the table below. Each can also be individually tested under different conditions and parameters via double-click.

Category Notes    Category Notes
  Motion Moves sprites and
changes angles
     Events Contains event handlers
placed on the top of each group of blocks
  Looks Controls visibility,
costumes, and output
  Control If statements and
loop structures
  Sound Plays audio files and
programmable sequenced audio
  Sensing All sprite hit detection
and user input
  Pen Allows for
turtle graphics
  Operators Mathematical and
Boolean operators such as finding the username of the project's user.
  Data Variable usage
and assignment
  More Blocks Custom procedures (blocks) and external devices control.
Hello, World! in Scratch

Besides the Script tab, there are two additional tabs, the Costumes tab and the Sounds tab. An expandable bar at the right is Help area.

In comparison to the previous versions of Scratch, the areas have been rearranged in version 2.0, as previously the blocks palette was in the left area, the selected sprite area and scripts area associated with a selected sprite were in the middle of the screen, and the stage area with sprites thumbnails listed below it were in the right area of the screen.[6]

Community of users[edit]

The Scratch website after the release of public project sharing

Scratch is used in many different settings: schools,[7] museums,[8] community centers, and homes. For example, younger children can create projects with their parents or older siblings, and college students use Scratch in some introductory computer science classes (including Harvard's introductory computer class).[9][10] Via localization files downloaded with Scratch its interface language can be changed to a language of choice since Scratch is used in different parts of the world. The Johns Hopkins University Center for Talented Youth offers an online course on Scratch programming for students in grade 6 and up through the CTYOnline program.[11]

Empirical studies were made of various features[citation needed]—those that interfered with intuitive learning were discarded, while those that encouraged beginners and made it easy for them to explore and learn were kept. Some of the results are surprising, making Scratch quite different from other teaching languages (such as BASIC, Logo, or Alice).

Online community[edit]

The Scratch online community's slogan "Imagine, Program, Share" indicates that sharing and the social aspects of creativity are important parts of the philosophy behind Scratch.[12] A few influential members of the Scratch online community made great personal strides in innovative methods with scratch programming.

Scratch projects are not seen as "black boxes", but as objects for remixing to make new projects. Projects can be uploaded directly from the development environment to the Scratch website and any member of the community can download their full source code to study or to remix into new projects.[13][14] Members can also create project studios, comment, tag, favorite and "love" others' projects, follow another member to see their projects and activity, and share ideas. Projects range from games to animations to chatbots. All projects on the website are shared under a Creative Commons attribution and share-alike license and can be played in a web browser (using the Flash Player, which is not available for iOS devices). The website receives close to 10 million page views per month[15] and as of August 10, 2014 it had 3,726,565 registered members (however, only 402,697 users have shared projects), and over 6,100,000 projects (every minute more than one project gets uploaded).[16] The website frequently establishes "Scratch Design Studio" challenges to encourage creation and sharing by providing users with a basic design concept. There are custom home pages for Mexico and Israel that display local content in some sections of the home page. Scratch has participated in Hour of Code several times. There are also local independent Scratch websites in countries such as Portugal[17] and the United Arab Emirates.[18] In 2008, the Scratch online community platform (named "ScratchR") received an honorary mention in the Ars Electronica Prix.[19] There is also an online community for educators, called ScratchEd.[20] Scratch is also a fun literary structure, with online roleplays that range in many different genres.

Features and derivatives[edit]

The current version of Scratch does not treat procedures as first class structures and has limited file I/O options with Scratch 2.0 Extension Protocol; an experimental extension feature that allows interaction between Scratch 2.0 and other programs. [21] The Extension protocol allows interfacing with hardware boards such as Lego Mindstorms or Arduino.[22] In addition Scratch 2 only supports one-dimensional arrays, known as "lists". Floating point scalars and strings are supported as of version 1.4, but with limited string manipulation capability. There is a strong contrast between the powerful multimedia functions and multi-threaded programming style and the rather limited scope of the Scratch programming language. On May 6, 2013, Scratch closed for 3 days to update to Scratch 2.0. The update changed the look of the site and included an online project editor. A new beta version of the Scratch 2 Offline Editor is currently available. This version replaces the old Scratch 2.0. [23]

A number of Scratch derivatives[24] called Scratch Modifications have been created using the source code of Scratch version 1.4. These programs are a variation of Scratch that normally include a few extra blocks[25] or changes to the GUI.

Some of them additionally introduce shifts in underlying approach to computing, such as Snap! programming language, featuring first class procedures (their mathematical foundations are called also "Lambda calculus"), first class lists (including lists of lists), and first class truly object oriented sprites with prototyping inheritance, and nestable sprites, which are not part of Scratch.[26] Snap! (its previous version was called BYOB) was developed by Jens Mönig[27][28] with documentation provided by Brian Harvey[29][30] from University of California, Berkeley and has been used to teach "The Beauty and Joy of Computing" introductory course in CS for non-CS-major students.[31]

The source-code of Scratch and its derivatives are based on Squeak, which is based on Smalltalk-80. Version 2 of Scratch is implemented in ActionScript, with an experimental JavaScript-based interpreter being developed in parallel.[32]

Catrobat is a visual programming language for smartphones and tablets inspired by Scratch. Pocket Code is an app with which you can create, download and upload programs created in Catrobat. Catrobat and Pocket Code are available under open source licenses.[33][34]

See also[edit]

The following youth computing projects also originated in the MIT Lifelong Kindergarten Group:

Other educational programming languages include:


  1. ^ "Updated Scratch 2.0 Offline (Beta) is now available!". Scratch. 29 August 2013. Retrieved 25 January 2014. 
  2. ^ "Scratch 20 Preview". YouTube. MITScratchTeam. 1 May 2013. Retrieved 25 January 2014. 
  3. ^ "Scratch source-code download page". Scratch Documentation Site. Retrieved 25 January 2014. 
  4. ^ Schorow, Stephanie (14 May 2007). "Creating from Scratch". MIT News Office. Retrieved 25 January 2014. 
  5. ^ Kids’ Programming Tool Scratch Now Runs In The Browser, TechCrunch, May 2013.
  6. ^ Maloney, John; Hernández, Andrés; Rusk, Natalie; Eastmond, Evelyn; Brennan, Karen; Millner, Amon; Rosenbaum, Eric; Silver, Jay; Silverman, Brian; Kafai, Yasmin (November 2009). "Scratch: Programming for All". Communications of the ACM 52 (11): 60–67. doi:10.1145/1592761.1592779. Retrieved 25 January 2014. 
  7. ^ "Canadian schools starting to teach computer coding to kids". 2014-04-30. Retrieved 2014-04-30. 
  8. ^ "Scratch Day". Science Museum of Minnesota. Archived from the original on 8 April 2013. Retrieved 25 January 2014. 
  9. ^ "Scratch for budding computer scientists". ACM SIGCSE Bulletin 39 (1): 223–7. March 2007. doi:10.1145/1227310.1227388. ISBN 1-59593-361-1. 
  10. ^ Malan, David. "Scratch for Budding Computer Scientists". Harvard School of Engineering and Applied Sciences. Retrieved 25 January 2014. 
  11. ^ "Scratch Programming". Johns Hopkins Center for Talented Youth. 
  12. ^ Monroy-Hernández, A.; Resnick, M. (March 2008). "Empowering kids to create and share programmable media" (PDF). ACM interactions 15 (2): 50–53. doi:10.1145/1340961.1340974. 
  13. ^ Monroy-Hernandez, Andres; Hill, Benjamin Mako; Gonzalez-Rivero, Jazmin; Boyd, Danah (2011). "Computers Can't Give Credit: How Automatic Attribution Falls Short in an Online Remixing Community". Proceedings of the 29th International Conference on Human Factors in Computing Systems (CHI '11). ACM. pp. 3421–30. doi:10.1145/1978942.1979452. 
  14. ^ B.M; Monroy-Hernández, A.; Olson, K.R. (2010). "Responses to remixing on a social media sharing website". ICWSM 2010 : Proceedings of the Fourth International Conference on Weblogs and Social Media, May 23–26, 2010. Washington, D.C.: AAAI Press. ISBN 9781577354451. OCLC 844857775. 
  15. ^ "Traffic and Demographic Statistics by Quantcast". Quantcast. Retrieved 25 January 2014. 
  16. ^ "Scratch Statistics". Scratch. Retrieved 25 January 2014. 
  17. ^ "Scratch". Scratch (in Portuguese). 
  18. ^ "Scratch". Scratch (in Arabic). Retrieved 25 January 2014. 
  19. ^ "Prix Ars Electronica". Ars Electronica. Archived from the original on 6 July 2011. Retrieved 25 July 2014. 
  20. ^ "ScratchEd". ScratchEd. Retrieved 25 January 2014. 
  21. ^ "Scratch Extension Protocol (2.0)". MIT. 
  22. ^ "Preliminary Scratch extension for talking to Arduino boards running Firmata". Scratch extension GitHub. Damellis. 
  23. ^ "Updated Scratch 2 Offline Editor". Scratch Announcement homepage. MIT. 
  24. ^ "Scratch Modification". Scratch Wiki. Lifelong Kindergarten Group at the MIT Media Lab. 
  25. ^ "Blocks". Scratch Wiki. 
  26. ^ "BYOB homepage". University of California, Berkeley. 
  27. ^ Mönig, Jens (June 2007). "Jens on Scratch". Scratch. Retrieved 25 January 2014. 
  28. ^ "Mönig's blog post announcing BYOB as bringing protypal inheritance to Scratch". Chirp. 31 May 2011. Retrieved 25 January 2014. 
  29. ^ "HomePage for Brian Harvey". Electrical Engineering and Computer Sciences. Retrieved 25 January 2014. 
  30. ^ Harvey, Brian (July 2008). "Brian Harvey user contributions page". Scratch. Retrieved 25 January 2014. 
  31. ^ "The Beauty and Joy of Computing course homepage". EECS Instructional Support Group Home Page. Retrieved 25 January 2014. 
  32. ^ "We're seeking contributors to help finish our HTML5 Scratch player (now open sourced!)". Scratch. Retrieved 25 January 2014. 
  33. ^ Slany, Wolfgang; Koitz, Roxane: "Using Catrobat, a Scratch-like visual programming language for smartphones, in a middle school physics course", SPLASH Portland 2014.
  34. ^ Catrobat developer site.

External links[edit]