Glossary

This glossary defines key terms used throughout the Aptos documentation.

Abort Code : A numeric identifier indicating why a program terminated abnormally. In Move, it signals specific error conditions.

Aptos CLI : The command-line interface for the Aptos blockchain. It is used for compiling, testing, deploying, and interacting with Move packages.

Attributes : Special annotations in Move code, like #[test] or #[view], that provide metadata to the compiler or runtime, modifying the behavior of the annotated code.

BCS (Binary Canonical Serialization) : The deterministic serialization format used in Aptos. BCS ensures that data structures always serialize to the same byte representation, which is crucial for blockchain consensus.

Custom Error Type : A user-defined struct that provides detailed context for an error, offering a more informative alternative to simple abort codes.

Entry Function : A public function in a Move module, marked with the entry keyword, that can be directly invoked in a transaction.

Enum : A type that can hold one of several defined variants. Enums are useful for representing states or options in a type-safe way.

Error Propagation : The process where an error (abort) in one function causes its calling functions to also abort, passing the error up the call stack.

Error Range : A designated range of abort codes for a specific module to prevent conflicts and organize error handling.

Error Testing : The practice of writing tests to verify that functions fail as expected under error conditions, often using the #[expected_failure] attribute.

Event : A mechanism for Move contracts to emit data that can be indexed and queried by off-chain services, signaling that something of interest has occurred.

Expected Failure : A test attribute (#[expected_failure]) that asserts a test case should fail with a specific abort code, enabling robust error-handling tests.

Legacy Shortened Address : A condensed form of an Aptos address where leading zeros are omitted. These are automatically padded with zeros for compatibility.

Little-endian : A byte-ordering scheme where the least significant byte is stored first. Aptos uses little-endian byte order for BCS serialization.

Module : A single file containing Move code (.move), which acts as a fundamental unit of code organization and encapsulation within a package.

Named Address : An alias for a specific account address used in Move source code. The actual address is substituted during compilation, making code more portable.

Package : A deployable unit of Move code that can contain one or more modules. It is published to the Aptos blockchain as a single entity.

Publish : The act of deploying a Move package to the Aptos blockchain, making its code and resources available on-chain.

Resource : A special struct with the key ability that represents data stored in an account's global storage. Resources have ownership semantics and cannot be copied or discarded.

Storage Slot : A location in the blockchain's global state, identified by a 32-byte address, where data (like accounts or objects) can be stored.

Struct : A composite data type that groups related values into a single, named structure. Its behavior is defined by its abilities (copy, drop, store, key).

Tuple : A fixed-size, ordered collection of values that can have different types.

ULEB128 (Unsigned Little-Endian Base-128) : A variable-length encoding for unsigned integers used in BCS, primarily for representing the length of sequences efficiently.

View Function : A read-only function marked with the #[view] attribute. It can be called to query blockchain state without submitting a transaction and incurring gas fees for state changes.