You failed everything!

Question

Your goal is simple: to fail everything. More precisely, you should write the shortest code that triggers a compilation/interpretation error, or a runtime error.

What does not count

• Failing with symbols that are not covered by the language syntax and are meant to appear only in string literals, comments and other ways to include non-executable data in the code, or are not meant to appear in the code at all
• Warnings and notices that don't prevent successful compilation or execution
• Overflow related errors: infinite loops, recursion limits reaching, stack overflows, out-of-memory errors and so on

This is code-golf, so the shortest code in bytes wins!

By the way, this is probably the only challenge where non-esoterical languages can beat esoterical ones ;-)

Answer 1

Polyglot, 0 bytes

This is a list of languages where an empty program gives an error.

• C/C++/Objective-C: Any compiler will complain not having a main, and emit a link error.
  • C (gcc), C (tcc), C (clang), C++ (gcc), C++ (clang), Objective-C (gcc), Objective-C (clang)
  • shortC
• Java: It's an error to not have a class to run.
  • Java (JDK), Java (OpenJDK)
  • Kotlin
  • Scala
• C#: Requires a static Main method.
  • .NET Core, Mono, Visual C#
• Pascal: Not having a BEGIN to begin with is an error.
  • Pascal, Object Pascal
• Visual Basic: Unlike other Basics, VB requires to have a Sub Main to run.
  • .NET Core, Mono, VBC
• Other languages that require some kind of main to compile and run.
  • B
  • D
  • Dart
  • Fortran (gfortran)
  • Go
  • Vala
  • (Add language here)
• Languages that require specific syntax elements to run correctly.
  • ArnoldC
  • Shakespeare Programming Language
  • Whitespace
  • Taxi
  • (Add language here)
• Languages that specifically reject empty files.
  • Chapel
  • (Add language here)
• Languages that segfault or otherwise show erroneous behavior with empty files. Some of these might be actually a bug in the compiler/interpreter.
  • Backhand: Tries to access the first instruction and throws an error.
  • Check is similarly bugged with empty code.
  • ecpp segfaults when an empty program is given.
  • Seed always gives error if the code isn't two integers with a space between them.
  • (Add language here)

Answer 2

60% of all coding languages, 1 byte

+ or - or / or * or % or any valid token etc.

To complement Bubbler's answer.

Answer 3

Polyglot, 1 byte

a

This gives undefined identifier error in many interpreted languages.

• Python
• Javascript
• APL
• J
• (Add language here)

Polyglot, 1 byte

+

This gives syntax error in many languages.

• (Add language here)

Polyglot, 1 byte

'

This gives open string literal error in many languages.

• (Add language here)

Polyglot, 1 byte

[

This gives open bracket error in many languages. (Feel free to change to ( or { if some languages specifically error with it.)

• (Add language here)

Answer 4

Attache, 1 byte

/

Try it online!

Crashes with:

AttacheUnimplementedError: (1:1) / is not defined for `NilClass`

Answer 5

Racket / Scheme / Lisp / Others?: 1 byte

) Will give an error for mismatched parentheses

Answer 6

Ahead, 1 byte

/

Tries to do 0/0. Reference implementation on TIO will fail with:

Exception in thread "main" java.lang.ArithmeticException: / by zero
        at ajc2.ahead.Head.doCell(Head.kt:148)
        at ajc2.ahead.Head.step(Head.kt:31)
        at ajc2.ahead.Runner.go(Runner.kt:6)
        at ajc2.ahead.MainKt.main(Main.kt:13)

Try it online!