We are very pleased to spread the first information about the 4th edition of the School on Foundations of Programming and Software Systems, to be held in Bertinoro on February 13-17, 2023. This will be the first edition of the school after the beginning of the COVID pandemic. The previous editions of the school took place in Porto [1], Oxford [2], and Warsaw [3]. The school is oriented to Master and PhD students, and to young scholars. It will be held at CEUB [4], which can be reached from Bologna in about 90 minutes. (We are considering, depending on the number of participants, to organize bus transfers to and from Bologna Airport on February 12 and 18, 2023). The main theme of this edition of FoPSS are the quantitative aspects of program semantics, verification, and transformation. The following researchers have accepted to give short courses or seminars as part of the school: Deepak Garg (MPI-SWS), on "Resource Analysis Using Types" Marco Gaboardi (Boston University), on "Relational Reasoning for Security and Privacy" Benjamin Kaminski (Saarland University), on "Quantitative Verification, Transformer-style" Delia Kesner (Université de Paris), on "Quantitative Types for Higher-Order Programming Languages" Aleks Kissinger (Oxford), on "Picturing Quantum Software" Damiano Mazza (CNRS), on "Introduction to Differentiable Programming" Prakash Panangaden (McGill), on "Bisimulation Metrics and Variations with Applications to Representation Learning" Christin Tasson (Sorbonne Université), on "Probabilistic Program Semantics" Valeria Vignudelli (CNRS), on "Equational Theories for Probabilistic Effects" Registration will cover participation to the school and accommodation at CEUB with half board. Thanks to the help of sponsors (including ETAPS, SIGLOG, SIGPLAN, the University of Bologna, and the DIAPASoN Project), we plan to keep the registration fee as low as possible. The reception capacity of the CEUB is big, but subject to limits. We therefore encourage those interested in participating to the school to pre-register by following the link below [5] and fill the form *by September 22, 2022*. This we will us to keep track of the numbers. A web page with more detailed information will soon be ready and accessible via [5]. We would be happy to answer any questions about the organization of the school. Just send us an email! Looking forward to seeing you in Bertinoro. Best Regards, Ugo Dal Lago, Francesco Gavazzo, Paolo Pistone. [1] https://probprogschool2017.di.uminho.pt/ [2] https://www.floc2018.org/fopss/ [3] https://www.mimuw.edu.pl/~fopss19/ [4] https://www.ceub.it/?lang=en [5] https://forms.gle/Z5sinvogkApZrgqaA