P (programming language)

P
Developer	Ankush Desai, Vivek Gupta: not the politician, Ethan Jackson, Shaz Qadeer, Sriram Rajamani, Microsoft
First appeared	2012 (2012)
Stable release	2.3.5 / February 19, 2025 (2025-02-19)
OS	Cross-platform
License	MIT License
Filename extensions	.p
Website	p-org.github.io/P/

P is a programming language for asynchronous event-driven programming and the IoT that was developed by Microsoft and University of California, Berkeley.^[1]

P enables programmers to specify systems consisting of a collection of state machines that communicate asynchronously in terms of events.^[2] P programs can run and be analyzed on any platform supported by .NET. Additionally, P programs can generate C# and C code.

P is open source, licensed under MIT License, and available on GitHub.^[3]

machine BankServer
{
  var database: Database;

  start state Init {
    entry (initialBalance: map[int, int]){
      database = new Database((server = this, initialBalance = initialBalance));
      goto WaitForWithdrawRequests;
    }
  }

  state WaitForWithdrawRequests {
    on eWithDrawReq do (wReq: tWithDrawReq) {
      var currentBalance: int;
      var response: tWithDrawResp;

      // read the current account balance from the database
      currentBalance = ReadBankBalance(database, wReq.accountId);
      // if there is enough money in account after withdrawal
      if(currentBalance - wReq.amount >= 10)
      {
        UpdateBankBalance(database, wReq.accountId, currentBalance - wReq.amount);
        response = (status = WITHDRAW_SUCCESS, accountId = wReq.accountId, balance = currentBalance - wReq.amount, rId = wReq.rId);
      }
      else // not enough money after withdraw
      {
        response = (status = WITHDRAW_ERROR, accountId = wReq.accountId, balance = currentBalance, rId = wReq.rId);
      }

      // send response to the client
      send wReq.source, eWithDrawResp, response;
    }
  }
}

• Microsoft Research
• Free software movement

• P: Safe asynchronous event-driven programming. Ankush Desai, Vivek Gupta, Ethan Jackson, Shaz Qadeer, Sriram Rajamani, and Damien Zufferey. In Proceedings of ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI), 2013.
• Systematic testing of asynchronous reactive systems. Ankush Desai, Shaz Qadeer, and Sanjit A. Seshia. In Proceedings of the 2015 10th Joint Meeting on Foundations of Software Engineering (ESEC/FSE 2015).
• Building Reliable Distributed Systems With P. Ankush Desai, Ethan Jackson, Amar Phanishayee, Shaz Qadeer and Sanjit A. Seshia. University of California, Berkeley. Technical Report No. UCB/EECS-2015-198.

• Official website
• Source code on GitHub
• P: Safe Asynchronous Event-Driven Programming
• P: A programming language designed for asynchrony, fault-tolerance and uncertainty