The **Oracle Call Interface** (**OCI**) is a native C language [API](https://www.educative.io/answers/definition-api) that allows for​ the creation of applications that can be used to manipulate data and schemas in an Oracle database. OCI supports datatypes, calling conventions, syntax, and semantics of various third-generation languages such as C, C++, COBOL, and FORTRAN.

<h2>Applications</h2>

Since OCI is highly reliable, it is used by several Oracle tools, including SQL*Plus, Real Application Testing (RAT), and Data-Pump. Language-specific interfaces like Oracle JDBC-OCI, Oracle Precompilers, and Oracle C++ Call Interface (OCCI) drivers are also built upon the OCI. The API is used by the R language's ROracle driver and other leading scripting language drivers such as node-oracledb, for Node.js, and PHP OCI8.

<h2>Functionality</h2>

OCI libraries provide the following functionality:
* Accessing objects on the Oracle server using SQL.
* Accessing, manipulating, and managing objects in the object cache by traversing pointers or REFs.
* Converting Oracle dates, strings, and numbers to C data types.
* Managing the size of the object cache's memory.

What is Oracle Call Interface?

A C API that enables app development for Oracle databases, supporting multiple languages and tools like SQL*Plus and Data-Pump, facilitating data access and manipulation.