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.