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C++ Language/Variables/LifetimeAndScope

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C++ Language
  1. Overview
  2. Preprocessing
    1. Macros
    2. Tokenization
    3. Preprocessing Strings
    4. Compile-time Constants
    5. Compile-time Assertions
    6. Conditional-Compilation
  3. Namespace
    1. Namespace Shortcuts
    2. Nesting
    3. Splitting across Files
    4. Named and Unnamed
  4. Type
    1. Hungarian Prefixes
    2. Boolean
    3. Literals
    4. Bitwise Representation
    5. Max Value
    6. Conversion
    7. Enumeration
    8. Shortcuts
    9. Variant
    10. RTTI: RunTime Type Information
  5. Variables
    1. Lifetime and Scope
    2. Initialization
    3. Uniform Initialization
    4. Initialize without Constructor
    5. Decomposing-Auto
    6. Define at Same Time as Type
  6. Indirection
    1. Pointers
    2. Typed NULL
    3. Arrays
    4. Reference Variables
    5. Rvalue-References
    6. Smart Pointers
  7. Expressions
    1. Precedence
    2. Chain of Assignment
  8. Program Flow
    1. Loops
    2. The break Statement
    3. Return Value
    4. Parameters
    5. Function Overloading
    6. Function-Pointer
    7. Deprecating a Function
  9. Objects
    1. Accessibility
    2. Unwanted Compiler-Generated Functions
    3. Constructors
    4. Destructors
    5. Const Members
    6. Static Members
    7. Inheritance
    8. Operator Overloading
    9. Nested Classes
    10. Pointer to Members
    11. Low-Level C Structures
  10. Templates
    1. Templated-Functions
    2. Templated-Classes
    3. Templated-Variables
    4. Template-Parameters
    5. Traits
    6. Metaprogramming
    7. Concepts
  11. Error Handling
    1. Returning an Error Code
    2. Assertions
    3. C++ Exception Handling
  12. Standard Libraries
    1. C-Runtime
    2. STL: Standard Template Library
    3. Strings
    4. IOStreams
    5. Filesystem Access
    6. Multithreading
    7. RNG: Random Number Generator
  13. Obsolete Features

A variable defined outside of all functions will have "static-lifetime" (it will exist throughout your software's entire duration). A variable defined inside some function could also have static-lifetime, but it would need to be marked by the static keyword. Otherwise, it would be a transient "local-variable" whose storage will disappear when that function ends.

A variable defined inside some function has "local-scope" (it can only be used from within that function, regardless of its lifetime). A variable defined outside of all functions has "global-scope" (it can be used by all subsequent functions). If you mark a globally-scoped variable by the static keyword, then it can only be used in this source file.

Additional information about lifetime and scope

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