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Sign is an esoteric programming language invented by User:A that is inspired be the "theoretical" recursion support of's signature system, and every proram is trivially a signature system supporting an extended wiki tag system. Every program can "theoretically" run on the signature system. Every index begins with the index 1.

Try it yourself: set your signature to ~~~~ and see what happens!

The results of Sign is usually non-deterministic, as the time that a program runs can vary every time.


Any other markdown item saves that markdown to the signature. If they are executed, they are no-ops.

~~~~ recursion of the signature
--~~~~ recursion with timestamp inserted to the back of the signature.
<span f="yyy 3" i="xxx 5"></span> If there is a yyy on position 3, insert xxx on position 5 of the signature. Negative indexes are possible; they index the program from the backmost index to the frontmost index, unlike what positive indexes do.
<br /> Break out of a level of recursion. If there are no levels to break out, stop the program.

Notes of programming in Sign

Writing programs will be very easy; however, finding a right time to run a program will be very hard. Usually, a program will run correctly if it is run at the valid time (the programmer will have to specify that time).

If the valid time to run that program has passed, the user will have to modify their program to make it run correctly.

Example programs

Hello, world! program

Hello, world!

Cat program

Replace this with input

Infinite loop


Shortest code to do infinite output


Finite loop: repeat 60 times

I have no idea how long one step will take; let's assume that it takes 1 minute to do that. This program should be run at 08:00, 28 June 2019 (UTC)

<span f="09:00, 28 June 2019 (UTC) -1" i="<br /> 53">--~~~~