For developing custom applications that integrate with SAP S/4HANA Cloud Public Edition (a pattern known as side-by-side extensibility), the SAP Business Technology Platform (BTP) is the designated platform. SAP provides two primary development environments for this purpose:

1. SAP Business Application Studio (BAS): This is the standard cloud-based Integrated Development Environment (IDE) for professional developers. It is tailored for building Fiori applications, full-stack applications using the SAP Cloud Application Programming Model (CAP), and other extensions.

2. SAP Build: This is SAP's strategic low-code/no-code (LCNC) platform. It empowers citizen developers and business users to rapidly create and extend applications, automate processes, and design business sites with minimal to no coding, accelerating development.

A. SAP Cloud Portal Service: This service is used to create and manage business sites (portals) that provide a unified access point to applications, not for developing the core application logic itself.

D. SAP HANA Cloud: This is a database-as-a-service (DBaaS). While a custom application would use it for data persistence, it is not a tool for building the application's user interface or business logic.

1. SAP Learning Hub: In the course S4CPB1 - SAP S/4HANA Cloud

public edition - Onboarding Fundamentals

Unit 5: Extensibility

Integration

and Data Migration

the lesson on "Side-by-Side Extensibility" explicitly identifies SAP Business Technology Platform as the environment for such developments

highlighting tools like SAP Business Application Studio for pro-code and SAP Build for low-code scenarios.

2. SAP Help Portal - SAP Business Technology Platform Documentation: The official documentation for "SAP Business Application Studio" describes it as "a modern development environment...tailored for the efficient development of business applications for the SAP Intelligent Enterprise." (See SAP Business Application Studio product page on help.sap.com).

3. SAP Help Portal - SAP Business Technology Platform Documentation: The official documentation for "SAP Build" describes it as a "unified low-code offering... to create and augment enterprise applications

automate processes

and design business sites with drag-and-drop simplicity." (See SAP Build product page on help.sap.com).