What Is an Undefined Value?

Undefined variables, as the name suggests, are undefined variables. When programming in a computer programming language, the compiler reports an error because an undefined or uninitialized variable is accessed, and the error message is often "undefined" or "is not defined" or "undeclared".

Undefined variables, as the name suggests, are undefined variables. When programming in a computer programming language, the compiler reported an error because an undefined variable was used.

C/C++ Undefined variable C / C ++

If an undefined variable is accessed in the program, such as a, the following error message will appear:

error :: 'a' undeclared

Matlab Undefined variable Matlab

If an uninitialized variable is accessed in the program, such as a, the following error message will appear:

Function or variable 'a' is not defined.

Python Undefined variable Python

If an undefined variable is accessed in the program, such as a, the following error message will appear:

NameError :: name 'a' is not defined