Your FoxPro applications, at home on a modern machine.

The ceiling that came with 32 bits is gone

Visual FoxPro is a 32-bit program, and that decides more than it appears to. It is why a table stops at two gigabytes, why a memo file stops at two gigabytes, and why a big report runs out of memory on a machine with plenty to spare. The limits are signed 32-bit numbers buried in the file handling, not a licensing decision anybody made.

FoxDev Studio is 64-bit throughout. Every file offset is 64-bit and a table is never read into memory at all, so the same .dbf that used to stop dead carries on into the hundreds of gigabytes. One thing to know before you lean on it: a table grown past two gigabytes will not open in Visual FoxPro again. If you still work in both, that is a one-way door.

A compiler, and a machine built to run what it makes

Visual FoxPro compiled your program to p-code and shipped a runtime to execute it. This is the same arrangement, made again: a compiler and a bytecode interpreter written in Rust and compiled to WebAssembly, so one machine runs your code wherever the application runs. The editor checks what you type through that very compiler, so what it underlines and what the runtime refuses cannot drift apart.

A running program is a fiber. When it needs something from the world outside (a message box, a modal form, the next record) it does not call out and block; it yields, the work is done while the machine is off the stack, and the answer is handed back. That is why MESSAGEBOX() stops your program without freezing the window behind it, why READ EVENTS waits without spinning, and whySetFocus can fire GotFocus, and Init can run while a form is still being built, in the order FoxPro always did it.

How the machine works and what it runs.

The form you see is the object tree, not a picture of it

A running form is a live tree of objects with the properties you would expect, and the interface is drawn straight from that tree by React. Each object watches only itself, so THISFORM.lblGreeting.Caption = cMsg repaints one label rather than the whole form. On a dense screen that is the difference between instant and sluggish.

The same tree is what the designer edits, one step earlier. There is no second model kept in step with the first, which is the usual place a form and its designer start telling different stories.

Your old libraries still load, though nothing here is 32-bit

An .fll is a 32-bit image, and every process in a 64-bit application is 64-bit, so nothing inside the application itself could ever open one. Rather than tell you it is impossible, SET LIBRARY TO starts a small 32-bit process whose only job is to hold your library, and the runtime talks to it. The calls are synchronous, because a program may call into a library halfway through an expression, and an answer that arrived later would not be an answer. It is measured against real libraries: the encryption library, FoxTools, and libraries built from Microsoft’s own API samples.

Nothing 64-bit needs the bridge: DECLARE ... DLL reaches a modern library in the same process, and automation objects are reached the way they always were. The old road stays open; it just is not the only one any more.