Opaque data type¶
In computer science, an opaque data type is a data type whose concrete data structure is not defined in an interface.
Core Idea¶
Opaque data type is treated here as the recurring data-type design identity summarized by this source-grounded definition: In computer science, an opaque data type is a data type whose concrete data structure is not defined in an interface. In computer science, an opaque data type is a data type whose concrete data structure is not defined in an interface. This enforces information hiding, since its values can only be manipulated by calling subroutines that have access to the missing information.
Scope of Application¶
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Uses in various languages. This second option allows the hidden information to be shared by two or more modules.
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Documented setting. Typical examples of opaque data types include handles for resources provided by an operating system to application software.
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Documented setting. For example, the POSIX standard for threads defines an application programming interface based on a number of opaque types that represent threads or synchronization primitives like mutexes or condition variables.
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Documented setting. Opaque data types are frequently used to implement abstract data types.
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Documented setting. For example, the standard library that forms part of the specification of the C programming language provides functions for file input and output that return or take values of type "pointer.
Clarity¶
A clear use of Opaque data type names the carrier, the operative relation, and the conditions under which the source treats the identity as present. The minimal definition is In computer science, an opaque data type is a data type whose concrete data structure is not defined in an interface.
Manages Complexity¶
Opaque data type compresses multiple data-type design details into a stable diagnostic relation. The source shows both the central mechanism—if the information provided by the interface is sufficient to determine the type's size, then clients can declare variables, fields, and arrays of that type, assign their values, and possibly compare them for equality.—and the practical consequence—some languages, such as C, allow the declaration of opaque records (structs).
Abstract Reasoning¶
- Type the carrier. Identify the data-type design entities to which the claim applies.
- State the relation. Use the source-grounded identity: In computer science, an opaque data type is a data type whose concrete data structure is not defined in an interface.
- Check operation and conditions. Indeed, in Java (and several other languages) records are always handled through pointers.
- Demand recognition evidence. This enforces information hiding, since its values can only be manipulated by calling subroutines that have access to the missing information. 5.
Knowledge Transfer¶
Within the home domain. Knowledge about Opaque data type transfers literally when a new case preserves the same carrier type, relation, and recognition test. This second option allows the hidden information to be shared by two or more modules. Typical examples of opaque data types include handles for resources provided by an operating system to application software. Beyond the home domain. No canonical parent is asserted for Opaque data type. An outside case receives the specialist name only when the same typed roles and rejection conditions can be filled literally; otherwise the comparison remains an analogy pending later graph densification.
Neighborhood in Abstraction Space¶
Opaque data type sits in a moderately populated region (51st percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.
Family — Computation Models & Complexity Classes (37 abstractions)
Nearest neighbors
- Capability-based addressing — 0.88
- Typing Environment — 0.87
- Rational data type — 0.85
- Categorial Grammar — 0.85
- Foreign key — 0.85
Computed from structural-signature embeddings · 2026-10-08