Scratch (programming language)

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ParadigmEvent-driven, block-based programming language
First appeared2002; 16 years ago (2002) (first prototype)
2007; 11 years ago (2007) (public launch)
2013; 5 years ago (2013) (Scratch 2.0)
Implementation languageSqueak (Scratch 0.x, 1.x)
ActionScript (Scratch 2.0)
OSWindows, macOS, Linux
LicenseGPLv2 and Scratch Source Code License
Filename extensions.scratch (Scratch 0.x)
.sb, .sprite (Scratch 1.x)
.sb2, .sprite2 (Scratch 2.0+)
Influenced by
Logo, Smalltalk, HyperCard, StarLogo, AgentSheets, Etoys
ScratchJr, Snap!

Scratch is a visual programming language and online community targeted primarily at children, by coding with 'blocks' in the editor. Users of the site can create online projects using a block-like interface. The service is developed by the MIT Media Lab, has been translated into 70+ languages , and is used in most parts of the world.[1] Scratch is taught and used in after-school centers, schools, and colleges, as well as other public knowledge institutions. As of December 2018, community statistics on the language's official website show more than 41 million projects shared.[2]

Origin of name[edit]

Scratching is a technique used by disc jockeys to mix music clips together in creative ways and produce different sound effects by manipulating vinyl records on a turntable. Scratch takes its name from this technique, as it lets users mix together different media (including graphics, sound and other programs) in creative ways by "remixing" projects.[3][4]


Scratch encourages the sharing, reuse and combination of code, as indicated by their slogan, "Imagine, Program, Share".[5] Users can make their own projects, or they may choose to "remix" someone else's project. Projects created and remixed with Scratch are licensed under the Creative Commons Attribution-Share Alike License.[6] Scratch will automatically give credit to the user who created the original project and program.[3]

It is part of a research to design new technologies to enhance learning in after-school centers and other informal education settings, and broaden opportunities for youth who can possibly become designers and inventors. Scratch was 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.[7]


The new Scratch homepage skin

The MIT Media Lab's Lifelong Kindergarten group, led by Mitchel Resnick, in partnership with the Montreal-based consulting firm, the Playful Invention Company, co-founded by Brian Silverman and Paula Bonta, together developed the first desktop-only version of Scratch in 2003.

On May 6, 2013, Scratch closed for three days to update to Scratch 2.0. The update changed the look of the site and included an online project editor. An offline Scratch 2 Editor is also available.[8] Scratch 2 was released on May 9, 2013.[9] With its introduction, custom blocks can be defined within projects.[10]

As of 2017, Scratch 2 is available online and as an application for Windows, macOS, Linux (Adobe Air required), and unofficially for Android as an APK file. The Scratch 2.0 Offline editor can be downloaded for Windows, Mac and Linux directly from Scratch's website. However, the unofficial mobile version must be downloaded from the Scratch forums.[11][12]

The Scratch 3.0 interface includes many new features.
The Scratch 3.0 interface.

Scratch 3.0 has been released as a beta[13] and is available for use on most browsers, with the notable exception of Internet Explorer.[14] It features a language translation block, the stage's presence on the right-hand side of the screen (rather than the left), and a fresher interface.

Educational use[edit]

Scratch was popular in the United Kingdom through Code Clubs. Scratch is used as the introductory language because creation of interesting programs is relatively easy, and skills learned can be applied to other basic programming languages such as Python and Java.

Comparison of Scratch 1.4 and Scratch 2

Scratch is not exclusively for creating games. With the provided visuals, programmers can create animations, text, and more. There are already many programs which students can use to learn topics in math, history, and even photography. Scratch allows teachers to create conceptual and visual lessons and science lab assignments with animations that help visualize difficult concepts. Within the social sciences, instructors can create quizzes, games, and tutorials with interactive elements. Using Scratch allows young people to understand the logic of programming and how to creatively build and collaborate.[15] Scratch lets students create "meaningful personal as well as educational projects" which gives students a "practical tool" to express themselves after learning to use the language.[3]

Scratch is taught to more than 800 schools and 70 colleges of DAV organization in India and across the world.[16][17]

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 switched his course's language to C after the first week.[18][19]

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. The stage is 480 pixels wide, and 360 pixels tall, x:240 being the far right, x:-240 being the far left, y:180 being the top, and y:-180 being the bottom.[9]

There are many ways to create personal sprites and backgrounds. First, users can draw their own sprite manually with "Paint Editor" provided by Scratch.[9] 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.[20]

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, changes angles and changes X and Y values.      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, transparency, shade   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
  Pen Draw on the canvas by controlling pen width, color, and shade. Allows for turtle graphics.   Operators Mathematical operators, random number generator, and-or statement that compares sprite positions
  Data Variable and List usage and assignment   More Blocks Custom procedures (blocks) and external devices control and can import from PicoBoard or Lego WeDo 1.0/2.0
Hello, World! in Scratch

Besides the Scripts 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 users can change the look of the sprite in order to create various effects, including animation.[9] And the last tab is the Sounds tab, where users insert sounds and music to a sprite.[20]

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.[21]

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,[22] museums,[23] libraries,[3] community centers, and homes. Although Scratch’s main user age group is 8–18 years of age, Scratch has also been created for educators and parents. This wide outreach has created many surrounding communities, both physical and digital.[24]

Online community[edit]

On Scratch, members have the capability to share their projects and get feedback. Projects can be uploaded directly from the development environment to the Scratch website and any member of the community can download the full source code to study or to remix into new projects.[25][26] Members can also create project studios, comment, tag, favorite, and "love" others' projects, follow other members to see their projects and activity, and share ideas. Projects range from games to animations to practical tools. Additionally, to encourage creation and sharing amongst users, the website frequently establishes "Scratch Design Studio" challenges.[27]

The MIT Scratch Team ensures that this community maintains a friendly and respectful environment for people of all ages, races, ethnicities, religions, sexual orientations, and gender identities. All members are asked to provide feedback constructively and report any content that does not follow the community guidelines. To further ensure this community, the Scratch Team manages site activity and responds to reports on a daily basis.[28][29]

There is also an online community for educators, called ScratchEd. ScratchEd was developed and supported by the Harvard Graduate School of Education. In this community, Scratch educators share stories, exchange resources, ask questions, and find people.[30]

Scratch Wiki[edit]

The Scratch Wiki is a medium-sized wiki for the Scratch educational programming language and its website, history, and phenomena surrounding it. The wiki is supported by the Scratch Team (developers of Scratch), but is primarily written by Scratchers (users of Scratch) for information regarding projects and things interesting users.[31] However, Scratchers must have their accounts approved by Wiki administration to join.


Scratch Educators can gather in person at Scratch Educator Meetups. At these gatherings, Scratch Educators learn from each other and share ideas and strategies that support computational creativity.[32]

An annual "Scratch Day" is declared in May each year. Community members are encouraged to host an event on or around this day, large or small, that celebrates Scratch. These events are held worldwide, and a listing can be found on the Scratch Day website.[33]

Features and derivatives[edit]

Scratch uses event-driven programming with multiple active objects called sprites.[9] 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.

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.[34] The Extension protocol allows interfacing with hardware boards such as Lego Mindstorms[35] or Arduino.[36] 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.

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.[37]

A number of Scratch derivatives[38] 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[39] or changes to the GUI.

In July 2014, a program called ScratchJr was released for iPad. In 2016, ScratchJr was developed for Android. Although it was heavily inspired by Scratch and co-led by Mitch Resnick, the original creator of Scratch, it is nonetheless a complete rewrite designed for younger children.[40]

Some modifications 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.[41] Snap! (its previous version was called BYOB) was developed by Jens Mönig[42][43] with documentation provided by Brian Harvey[44][45] 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.[46]

See also[edit]

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


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External links[edit]