What is a module pool program in ABAP?

A module pool program (traditionally used to build classical SAP GUI transaction screens, distinct from simple report output) is structured around interactive screens with defined flow logic — each screen has associated PBO (Process Before Output) and PAI (Process After Input) modules controlling what happens before a screen displays and after the user submits input on it.

flowchart LR
    A[Screen triggered] --> B[PBO: prepare fields/data before display]
    B --> C[Screen displayed to user]
    C --> D[User submits input]
    D --> E[PAI: validate/process the input]
    E --> F{Navigate to another screen?}
    F -->|Yes| A

This is the traditional way to build custom, multi-screen transactions in classical SAP development — more complex to set up than a simple report program, but necessary for interactive transactions where users navigate between multiple related screens, entering and validating data along the way.

Invest now in Acorns!!! 🚀
Join Acorns and get your $5 bonus!

Acorns is a micro-investing app that automatically invests your "spare change" from daily purchases into diversified, expert-built portfolios of ETFs. It is designed for beginners, allowing you to start investing with as little as $5. The service automates saving and investing. Disclosure: I may receive a referral bonus.

Invest now!!! Get Free equity stock (US, UK only)!

Use Robinhood app to invest in stocks. It is safe and secure. Use the Referral link to claim your free stock when you sign up!.

The Robinhood app makes it easy to trade stocks, crypto and more.

Webull! Receive free stock by signing up using the link: Webull signup.