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→Architecture: Explain processes and RAMPIDs
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The kernel runs in supervisor mode on the PowerPC, and performs the basic tasks of a microkernel. It is responsible for process isolation, memory management, and interrupt dispatching, as well as communication with [[IOSU]]. Cafe OS applications run as user mode processes, with separate address spaces and W^X memory protection. The kernel provides basic [[Cafe_OS_Syscalls|syscalls]] for running processes.
The kernel runs in supervisor mode on the PowerPC, and performs the basic tasks of a microkernel. It is responsible for process isolation, memory management, and interrupt dispatching, as well as communication with [[IOSU]]. Cafe OS applications run as user mode processes, with separate address spaces and W^X memory protection. The kernel provides basic [[Cafe_OS_Syscalls|syscalls]] for running processes.
+
+===Processes===
+A process in Cafe OS represents a single running application, with its own code, memory, and permissions. Cafe OS only executes the code of a single process at a time, but it can hold the data of multiple processes in memory simultaneously, and switch between them. Rather than allowing arbitrary process creation, there is RAM reserved for a single foreground app, a single background app, and various other special processes. Each running process is assigned a unique identifier called a RAMPID:
+{| class="wikitable"
+|-
+! RAMPID
+! Description
+|-
+| 0
+| Cafe OS
+|-
+| 1
+| root.rpx
+|-
+| 2
+| ???
+|-
+| 3
+| ???
+|-
+| 4
+| Background app
+|-
+| 5
+| Home Menu
+|-
+| 6
+| Error display
+|-
+| 7
+| Foreground app
+|}
+
+In addition to RAMPID, Cafe OS processes have another type of process ID called a fixed process ID (PFID). Rather than representing which part of memory a process occupies, PFID actually specifies which specific app/task is running.
===Loader===
===Loader===