Application Binary Interface

1 min read

Pronunciation

[ap-li-kay-shun bi-när-ee in-ter-face]

Analogy

is like a file that tells you how to call methods in a library and interpret responses.

Definition

: The standardized interface between and external callers, defining how to encode/decode function calls and events.

Key Points Intro

specifications ensure interoperability by:

Key Points

Function selectors: First 4 bytes of calldata specify method.

Type encoding: Defines how to pack ints, strings, arrays.

Event logs: ABI describes log topics and data layout.

JSON schema: Human‑readable ABI files for tooling.

Example

Web3.js uses a contract’s JSON to encode an "transfer(address,uint256)" call when sending tokens.

Technical Deep Dive

encoding follows the spec: values are right‑aligned in 32‑byte slots. Dynamic types use head/tail pointers. The selector = first 4 bytes of keccak256(function signature). Decoding reverses the process using type definitions.

Security Warning

Incorrect can lead to malformed calls and lost funds; always use the provided by the contract author.

Caveat

does not enforce access control—callers still need correct permissions in contract logic.

Related Terms

Solidity

EVM

Bytecode

Blockchain & Cryptocurrency Glossary

Application Binary Interface - Related Articles