datalayout

Datalayout refers to the arrangement of data within a storage or memory representation, including how data types are sized, aligned, ordered, and encoded. It covers the physical layout of data structures in memory or on disk, such as field order, padding between fields, alignment requirements, endianness, and the byte representation of primitive types. The term is used in contexts such as programming languages, compilers, data serialization, and database storage, where the exact layout determines how data is read, written, and interpreted by software components.

In programming languages and compiler technology, data layout describes how aggregate types like structs and classes place their fields, what alignment they require, and how pointers and references are represented. This layout is often governed by the target architecture's application binary interface (ABI). Endianness (little- or big-endian) and the sizes of integers and floating-point values can vary by platform, making cross-architecture portability a concern. Developers may encounter different layouts across compilers or when enabling optimizations or packing pragmas.

In data interchange and storage, the data layout defines how serialized data is laid out in binary formats or transmitted over networks. Protocols and file formats specify field order, size, alignment, and endianness to ensure that different systems can encode and decode data consistently.

Practical considerations include using well-defined, fixed-width types, avoiding reliance on unspecified padding, and documenting the expected layout for APIs and interfaces. Tools and compilers expose the data layout for a target so that code generation and data access can be correct and efficient. See also ABI, memory layout, and data serialization.

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