What is mean by garbage value?

Answer 1

Garbage value or garbage data is programmers' slang for malformed data, typically with no correlation to the intended or expected value set.

For example, a function F might be designed to return a student's name, consisting of a string of readable characters, terminated by a null-bytes. When the function returns unintelligible data instead, data which doesn't form a valid name in any of the supported languages, the data returned by F is said to be garbage data.

Note that garbage data is not used to describe incorrect data. If, for example, function F returns the name Smith where Miller might have been the correct answer, function F would suffer from an error and the result data would be erroneous or incorrect, but not garbage.