Variable Scope Part 2 of 3

Richard Almanza | Mar 26, 2026 min read
Variable Scope Part 2 of 3

The following article is part of a series of posts I made on a Discord server.

Original publication date: 2024-09-27

— Previous: Variable Scope (Part 1 of 3)

Variable Scope (Part 2 of 3)

Examples

Variable accessibility depending on the relationship between blocks

(image-1) Global variables can be accessed from any part of the program; there isn’t much to consider here.

image-1 Image shows accessibility depending on where the call is made

Now, for local variables:

  • Inside FunctionC, there is a request to access (or modify) VariableA. This variable was created within FunctionA, and FunctionC is also nested within FunctionA. By the way, every child block dies before its parent block. Based on this, VariableA is alive and accessible throughout the entire lifetime of FunctionC, provided that VariableA was created before FunctionC.

  • In FunctionB, access to VariableC is requested, but this variable only exists during the lifetime of FunctionD. If the request is made before FunctionD, then VariableC hasn’t been created yet; if it is made after FunctionD, then it is already dead. Basically, the parent block cannot access the variables of the child block.

  • Finally, inside FunctionD, a request is made for VariableB, which lives in FunctionA. However, FunctionD is a “nephew” of FunctionA and they do not exist at the same time.

Sibling blocks do not live at the same time; one sibling block lives and dies before or after another. (We break this statement with parallelism and concurrency, but now is not the time to get into that).

(image-2) In this presentation, it is easier to observe the accessibility of variables depending on the block relationship.

image-2 Image shows the blocks and spaces where variables exist

  • Child blocks are directly above their parent block.

  • Sibling blocks are located at the same level.

  • Additionally, the lifetimes of the blocks can be represented on the horizontal axis and do not overlap.

The arrows indicate the direction of the request for a variable, and just like in image-1, variables outside their own block only continue to live if they belong to the parent block and/or direct ancestry.

— Downloads

Excalidraw File

— End of section

— Next: Variable Scope (Part 3 of 3)