Scratch (programming language)

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Paradigm Event-driven, block-based programming language
Developer MIT Media Lab Lifelong Kindergarten Group
First appeared 2002; 16 years ago (2002) (first prototype).
2007; 11 years ago (2007) (public launch).
2013; 5 years ago (2013) (Scratch 2.0)
Typing discipline Dynamic
Implementation language Squeak (Scratch 0.x, 1.x)
ActionScript (Scratch 2.0)
HTML5 (Scratch 3.0)
OS Windows, macOS, Linux
License GPLv2 and Scratch Source Code License
Filename extensions .scratch (Scratch 0.x)
.sb, .sprite (Scratch 1.x)
.sb2, .sprite2 (Scratch 2.0+)
Major implementations
Influenced by
Logo, Smalltalk, HyperCard, StarLogo, AgentSheets, Etoys
ScratchJr, Snap!

Scratch is a visual programming language and online community targeted primarily at children. Using Scratch, users can create online projects and develop them into almost anything by using a simple block-like interface. When they are ready, they then share, and also discuss their creations with each other. Developed by the Lifelong Kindergarten group at the MIT Media Lab,[1] the service is designed to help children (ages 8 and up) learn to utilize their imaginations, practice common sense, and, most importantly, to interact with computers.

Scratch is translated into 70+ languages and is used in homes, schools, and after-school clubs in every country in the world.[2] Scratch is often used in teaching coding, computer science, and computational thinking. Teachers also use it as a tool across many other subjects including math, science, history, geography, and art.

As of May 2018, there are more than 31,932,249 projects shared, 28,361,710 users registered, 156,310,759 comments posted, 4,533,610 studios created.[3] The blocks-based grammar of Scratch has influenced many other programming environments and is now considered a standard for introductory coding experiences for children.[citation needed]

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.[4][5]


Scratch encourages the sharing, reuse and combination of code. Their slogan is "Imagine, Program, Share". Users are also allowed to create “remixes” of another user’s project.[6] Projects created and remixed with Scratch are licensed under the Creative Commons Attribution-Share Alike License.[7] Scratch automatically gives 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, enabling young people to design and program projects that are meaningful to themselves and their communities.[8]


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. Its purpose was to aid young people, mainly for ages 8 and up, to learn programming.[9]

Scratch 2 was released on May 9, 2013.[1] 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]

Educational use[edit]

Scratch was made 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.

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 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, the water cycle, Galileo Thermometer or Hooke's Law Experiment. Within the social sciences, instructors can create quizzes, games, and tutorials that stimulate the mind and interact with the student.[13] Using Scratch allows young people to understand the logic of programming and how to creatively build and collaborate.[14] 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.[4]

Scratch is taught to more than 700 schools and 70 colleges of DAV organization in India and across the world.[15][16]

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.[17][18]

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.[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.[19]

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 and change 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.[1] And the last tab is the Sounds tab, where users insert sounds and music to a sprite.[19]

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.[20]

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,[21] museums,[22] libraries,[4] 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.[2]

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.[23]

For all Scratch members, there is an open learning community. This community allows members to explore and experiment with other Scratch members from all backgrounds, ages, and interests.[24]

In this community, members can share their projects, get feedback, and learn from one another. 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.[24][28]

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.[29]

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). The Scratch Wiki is a common source of information for scripts (code) and tutorials, and it continues to grow as Scratchers often use it for information. It currently has over 1,000 articles.

On December 6, 2008, a sole Wikia user by the name of LukeTek created the Scratch Programming Wiki, without Scratch Team involvement. He later transferred ownership to another user, JuiceyBox, who later also handed over to Lucario621, the only remaining founder. Lucario621 advertised the wiki in the Scratch website's Miscellaneous forum, thereby attracting many users' interest in the wiki. However, the articles were about specific Scratch projects, users, and other user-generated content, which deterred further interest in the wiki, and it fell dormant but continued to slowly grow.

Eventually, the wiki came to the attention of the Scratch Team. They approved of the concept, but the wiki as it was then had a few problems that needed to be solved:

  • The wiki contained advertisements.
  • The wiki was not on a domain.
  • It was impossible to certify that users on the wiki were who they said they were on Scratch.

To resolve these problems, three users, andresmh, JSO, and Lucario621, recreated the Scratch Wiki on MIT servers on June 3, 2010.[30] This resolved all three problems:

  • The wiki now did not contain advertisements.
  • The wiki was now on a domain (specifically,, though this was later changed to
  • The new account request system confirmed that users on the wiki were the same users on the main website.


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.[31]

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.[32]

Features and derivatives[edit]

Scratch uses 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.

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

A number of Scratch derivatives[37] 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[38] 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.[39]

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

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.[46]

See also[edit]

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

See also:


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External links[edit]