Scratch (programming language)

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Scratch (programming language)
Scratch Logo.svg Scratchcat.svg
Paradigm event-driven, imperative
Designed by Mitchel Resnick
Developer MIT Media Lab Lifelong Kindergarten Group
First appeared 2002; 14 years ago (2002) (test) 2005; 11 years ago (2005) (official)
Stable release 2.0 / May 13, 2013; 2 years ago (2013-05-13)
Typing discipline dynamic
Implementation language Squeak, ActionScript (Scratch 2.0)
OS Windows, OS X, Linux
License GPLv2 and Scratch Source Code License
Filename extensions .sb, .sprite (Scratch 1.4 and below) .sb2, .sprite2 (Scratch 2.0 or later)
Major implementations
Influenced by
Logo, Smalltalk, HyperCard, StarLogo, AgentSheets, Etoys
Scratch Jr, Snap!

Scratch is a visual programming language.[1] It is currently free. Scratch is used by students, scholars, teachers, and parents to easily create games and provide a stepping stone to the more advanced world of computer programming. It can also be used for a range of educational and entertainment constructionist 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.[2] 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.[1] Sprites can be drawn, as vector or bitmap graphics, from scratch in a simple editor that is part of Scratch, or can be imported from external sources, including webcams.

As of 2013, Scratch 2 is available online and as an application for Windows, OS X, and Linux.[3][4] The source code of Scratch 1.x is released under GPLv2 license and Scratch Source Code License.[5]

Origin of name[edit]

“Scratching” in the language of computer science means to reuse code that can be beneficial and effectively used for other purposes and easily combined, shared and adapted to new scenarios, which is a key feature in Scratch – “remix”, in which users can download and build up on public projects uploaded and developed by other users. It also gives credit to the participant who built on the original work and to the participant who created the original program.[6] The name was derived from turntablism's technique of scratching[6][7] (i.e., mixing sounds), relating the ease of mixing sounds to the ease of mixing projects made with Scratch.


Scratch was developed as a networked, media-rich programming environment, designed specifically to enhance the development of technological fluency at after-school cares in economically disadvantaged communities, grounded in the practices and social dynamics of the Computer Clubhouse, a network of after-school cares where youth (ages 5–18) from low-income communities learn to express themselves with new technologies. The researchers studied how Clubhouse youth learned to use Scratch to design and program new types of digital-arts projects, such as sensor-controlled music compositions, special-effects videos created with programmable image-processing filters, robotic puppets with embedded controllers and animated characters. Scratch's networking infrastructure, coupled with its multilingual abilities, enabled youth to share their digital-arts creations with other youth across boundaries of geography, language, and culture.

This research advanced understanding of the effective and innovative design of new technologies to enhance learning in after-school centers and other informal-education settings, and broadened opportunities for youth from under-represented groups who became designers and inventors with new technologies. Scratch was iteratively developed based on ongoing interaction with youth and staff at Computer Clubhouses. The use of Scratch at Computer Clubhouses served as a model for other after-school centers demonstrating how informal-learning settings can support the development of technological fluency, enabling young people to design and program projects that are meaningful to themselves and their communities.[8]

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. Its purpose was to aid young people, mainly for ages 8 and up, to learn programming.[9] Since 2007, projects could be shared online with other users and shared projects could be "remixed" (i.e., saved with changes) by other users.

The first web-based Scratch in 2005
The new Scratch homepage theme

Scratch 2 was released in May 2013.[1] With its introduction, custom blocks can be defined within projects.[10]

In 2015, the Scratch homepage was updated with a new theme. As of January 17th 2016, only the homepage had been updated with this new theme and the rest of the site continued to use the old theme.

Educational use[edit]

Scratch was made popular in the UK through Code Clubs. These use Scratch as the introductory language because of its relative ease to make interesting programs and because skills learnt through Scratch can be applied to other basic programming languages like Python and Java.

Scratch is not exclusively for creating programs, since it provides a lot of visuals, programmers can create animated stories such as “The Pizza Dude”, “Haiku”, or “Gemclan”. For older students, they can use Photo Journalism that teaches the basic background of journalism. Students that want to specialize in math can use Lemonade Stand, “Dino Odd and Even”, “Data Workshop”, or “Ellipserator” that mainly focuses on geometry. Scratch flexibility allows teachers to create conceptual and visual lessons and science lab assignments, as Scratch is a useful tool to create animations that help visualize difficult concepts such as plant cell mitosis, water cycle, Galileo Thermometer and Hooke’s Law Experiment. Within the social sciences, instructors can create quizzes, games and tutorials that stimulate the mind and interact with the student.[11] Using Scratch allows young people to understand the logic of programming and how to creatively build and collaborate.[12] Scratch lets students create "meaningful personal as well as educational projects" which allows students a "practical tool" to express themselves after learning to use the language.[6]

Harvard University lecturer Dr. David J. Malan prefers using Scratch over commonly used introductory programming languages, such as Java or C, in his introductory computer science course. However, there is a limited benefit in a college level education. Malan switches his course’s language to C after the first week.[13][14]

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. The stage uses x and y coordinates, with 0,0 being the stage center.[1]

There are many ways to create personal sprites and backgrounds. First, users can draw their own sprite manually with "Paint Editor" provided by Scratch.[1] Second, users can choose a Sprite from the Scratch library that contains default sprite, user’s past creations, a picture using a camera, or clip art.[15]

With a sprite 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 the visuals of the sprite; attach speech or thought bubble, change of background, enlarge or shrink   Control Conditional if-else statement, “forever”, “repeat”, and “stop”
  Sound Plays audio files and programmable sequences   Sensing Sprites can interact with the surroundings the user has created and can import from PicoBoard or Lego WeDo
  Pen Draw on portrait by controlling pen width, color, and shade   Operators Mathematical operators, random number generator, and and-or statement that compares sprite positions
  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.

Next to the Scripts tab, there is the Costumes tab, where user can change the look of the sprite in order to create various effects, including animation.[1] And the last tab is the Sounds tab, where users insert sounds and music to a sprite.[15]

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.[16]

Community of users[edit]

The Scratch website after the release of public project sharing in late 2007

Scratch is used in many different settings: schools,[17] museums,[18] libraries,[6] community centers, and homes. For example, younger children can create projects using ScratchJr (Scratch Junior) or using Scratch with their parents or older siblings as it's quite simple, and college students use Scratch in some introductory computer science classes (including Harvard's introductory computer class).[19][20] 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.[21]

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.[22] 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.[23][24] 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 practical tools. Chat rooms are bot allowed. 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 unavailable for iOS devices). The website receives close to 10 million page views per month[25] 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).[26] 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[27] and the United Arab Emirates.[28] In 2008, the Scratch online community platform (named "ScratchR") received an honorary mention in the Ars Electronica Prix.[29] There is also an online community for educators, called ScratchEd.[30] Scratch is also a fun literary structure, with online roleplays, 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.[31] The Extension protocol allows interfacing with hardware boards such as Lego Mindstorms[32] or Arduino.[33] 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 ability. 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.[34]

A number of Scratch derivatives[35] called Scratch Modifications have been created using the source code of Scratch version 1.4. These programs are a variant of Scratch that normally include a few extra blocks[36] or changes to the GUI.

Some of them additionally introduce shifts in underlying approach to computing, such as the language Snap!, 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.[37] Snap! (its previous version was called BYOB) was developed by Jens Mönig[38][39] with documentation provided by Brian Harvey[40][41] 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.[42]

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.[43]

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 released under open source licenses.[44][45]

See also[edit]

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

Other educational programming languages include:


  1. ^ a b c d e f Marji, Majed (2014). Learn to Program with Scratch. San Francisco, California: No Starch Press. pp. xvii, 1–9, 13–15. ISBN 9781593275433. 
  2. ^ "Research on Scratch". Scratch. Retrieved 3 June 2015. 
  3. ^ "Updated Scratch 2.0 Offline (Beta) is now available!". Scratch. 29 August 2013. Retrieved 25 January 2014. 
  4. ^ "Scratch 20 Preview". YouTube. MITScratchTeam. 1 May 2013. Retrieved 25 January 2014. 
  5. ^ "Scratch source-code download page". Scratch Documentation Site. Retrieved 25 January 2014. 
  6. ^ a b c d Lamb, Annette; Johnson, Larry (April 2011). "Scratch: Computer Programming for 21st Century Learners". Teacher Librarian 38 (4): 64–68. Retrieved 18 July 2015. (subscription required (help)). 
  7. ^ Schorow, Stephanie (14 May 2007). "Creating from Scratch". MIT News Office. Retrieved 25 January 2014. 
  8. ^ Resnick, Mitchel. "A Networked, Media-Rich Programming Environment to Enhance Informal Learning and Technological Fluency at Community Technology Centers". National Science Foundation. Retrieved 3 June 2015. 
  9. ^ Shapiro, Jordan. "Your Five Year Old Can Learn To Code With An IPad App". Forbes Magazine. Retrieved April 23, 2015. 
  10. ^ Kids’ Programming Tool Scratch Now Runs In The Browser, TechCrunch, May 2013.
  11. ^ "Bookmarkable URL intermediate page". Retrieved 2015-05-09. 
  12. ^ Martin, Neil (25 June 2015). "What is Scratch? Is it AV or IT?". AV Magazine. Retrieved 18 July 2015. 
  13. ^ Young, Jeffrey R. (July 20, 2007). "Fun, Not Fear, Is at the Heart of Scratch, a New Programming Language". The Chronicle of Higher Education. ISSN 0009-5982. Retrieved 2015-05-09. 
  14. ^ "CS50 Syllabus". Retrieved 2015-05-17. 
  15. ^ a b "Science Buddies: Scratch User Guide: Installing & Getting Started with Scratch". Retrieved 2015-05-09. 
  16. ^ Resnick, Mitchel; 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. 
  17. ^ "Canadian schools starting to teach computer coding to kids". 2014-04-30. Retrieved 2014-04-30. 
  18. ^ "Scratch Day". Science Museum of Minnesota. Archived from the original on 8 April 2013. Retrieved 25 January 2014. 
  19. ^ "Scratch for budding computer scientists". ACM SIGCSE Bulletin 39 (1): 223–7. March 2007. doi:10.1145/1227310.1227388. ISBN 1-59593-361-1. 
  20. ^ Malan, David. "Scratch for Budding Computer Scientists". Harvard School of Engineering and Applied Sciences. Retrieved 25 January 2014. 
  21. ^ "Scratch Programming". Johns Hopkins Center for Talented Youth. 
  22. ^ 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. 
  23. ^ 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" (PDF). Proceedings of the 29th International Conference on Human Factors in Computing Systems (CHI '11). ACM. pp. 3421–30. doi:10.1145/1978942.1979452. 
  24. ^ Hill, 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. 
  25. ^ "Traffic and Demographic Statistics by Quantcast". Quantcast. Retrieved 25 January 2014. 
  26. ^ "Scratch Statistics". Scratch. Retrieved 25 January 2014. 
  27. ^ "Scratch". Scratch (in Portuguese). 
  28. ^ "Scratch". Scratch (in Arabic). Retrieved 25 January 2014. 
  29. ^ "Prix Ars Electronica". Ars Electronica. Archived from the original on 6 July 2011. Retrieved 25 July 2014. 
  30. ^ "ScratchEd". ScratchEd. Retrieved 25 January 2014. 
  31. ^ "Scratch Extension Protocol (2.0)". MIT. 
  32. ^ "EV3+Scratch Extension". Scratch extension GitHub. Code & Circuit. 
  33. ^ "Preliminary Scratch extension for talking to Arduino boards running Firmata". Scratch extension GitHub. Damellis. 
  34. ^ "Updated Scratch 2 Offline Editor". Scratch Announcement homepage. MIT. 
  35. ^ "Scratch Modification". Scratch Wiki. Lifelong Kindergarten Group at the MIT Media Lab. 
  36. ^ "Blocks". Scratch Wiki. 
  37. ^ "Snap! (Build Your Own Blocks) 4.0". BYOB homepage. University of California, Berkeley. 
  38. ^ Mönig, Jens (June 2007). "Jens on Scratch". Scratch. Retrieved 25 January 2014. 
  39. ^ "Mönig's blog post announcing BYOB as bringing protypal inheritance to Scratch". Chirp. 31 May 2011. Retrieved 25 January 2014. 
  40. ^ "HomePage for Brian Harvey". Electrical Engineering and Computer Sciences. Retrieved 25 January 2014. 
  41. ^ Harvey, Brian (July 2008). "Brian Harvey user contributions page". Scratch. Retrieved 25 January 2014. 
  42. ^ "The Beauty and Joy of Computing course homepage". EECS Instructional Support Group Home Page. Retrieved 25 January 2014. 
  43. ^ "We're seeking contributors to help finish our HTML5 Scratch player (now open sourced!)". Scratch. Retrieved 25 January 2014. 
  44. ^ Slany, Wolfgang; Koitz, Roxane: "Using Catrobat, a Scratch-like visual programming language for smartphones, in a middle school physics course", SPLASH Portland 2014.
  45. ^ Catrobat developer site.

External links[edit]