A variable-length name is stored using space for the characters it actually contains, rather than reserving the same fixed-size slot for every name. In compiler design, the term usually describes a way to store names in a symbol table—not a rule that programming-language identifiers can be any length.
What does “variable-length name” mean?
In a compiler’s symbol table, names such as identifiers can be stored in a shared sequence of characters. The compiler records where each name begins and how many characters belong to it. The name’s storage therefore varies with its length.
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For example, a sequence might contain Calculate, sum, a and b. Metadata identifying each name’s starting position and length lets the compiler locate the individual strings.
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How does variable-length storage differ from fixed-length storage?
| Aspect | Fixed-length storage | Variable-length storage |
|---|---|---|
| Space for each name | A slot with a set capacity, whether or not the name uses all of it. | Space for the characters in the name. |
| Finding a name | The fixed slot size helps determine where each entry begins. | Metadata such as a starting position and length identifies each entry. |
| What the layout tells you | The reserved capacity for a name. | The position and length of a stored name. |
The layout describes how names are represented; it does not, by itself, establish which approach is faster or how much memory either approach saves.
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Does it mean identifiers have no length limit?
No. Storage layout and identifier rules are separate. A programming language or tool can limit identifier spelling, specify permitted characters and case behavior, or reserve particular names, regardless of how a compiler stores the text internally.
C rules should not be treated as universal. Yale’s C programming notes discuss identifier conventions and note that modern C implementations no longer have the old external-name limit associated with very early C versions. They also caution that leading underscores are commonly used internally by system libraries: Yale CPSC 223 notes.
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Why do language and configuration matter?
SAS illustrates how identifier limits depend on a specific environment. The SAS 9.3 reference describes VALIDVARNAME=V7 as allowing variable names up to 32 characters, while VALIDVARNAME=ANY allows a broader set of characters and limits names to 32 bytes. Those are SAS 9.3 rules for the stated settings, not general limits for compiler names or programming-language identifiers: SAS 9.3 documentation on variable names.
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When checking a name limit, identify the language or tool, its version and configuration, and whether the limit is measured in characters or bytes.
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