95 ;;Quote: the Mach kernel provides a small set of primitive functions and abstractions for building complete system environments

95+;;Quote: Mach's primitive functions allow more complex services and resources to be represented as references to objects

95 ;;Quote: the Mach kernel supports four basic abstractions: tasks, threads, ports, and messages. These match multiprocessor hardware

95+;;Quote: a task is the basic unit of resource allocation. It includes a paged virtual address space and protected access to system resources

95+;;Quote: a thread is the basic unit of CPU utilization. All threads within a task share access to all task resources

95+;;Quote: a port is a protected, communication channel. Ports are Mach's named, reference objects

95+;;Quote: a message is a typed collection of data objects. They may contain an address space, pointers, and capabilities for ports

96 ;;Quote: operate on a Mach object by sending a message to a port

96+;;Quote: creating a task or thread returns a port for manipulating the task or thread

97 ;;Quote: Mach tasks form a tree structure defined by task creation; controls how memory is shared

97+;;Quote: a task can mark regions of virtual memory as read-write, copy-on-write, or not inherited by child tasks

97+;;Quote: a Unix fork operation is equivalent to a Mach task creating a child task with all memory copy-on-write

99 ;;Quote: Mach tasks may handle page faults and page-out data requests independently of the kernel

100 ;;Quote: virtual memory should separate machine independent data from machine dependent data

100+;;Quote: Mach's virtual memory is built on hardware page validate, invalidate, and protect

100+;;Quote: Mach implements virtual memory with address maps, share maps, VM objects, and page structures

102 ;;Quote: Mach ports may have multiple senders but only one receiver

102+;;Quote: Mach ports represent services or data structures; e.g., a window of a bitmap display

102+;;Quote: access to a port is granted by receiving a capability to send or receive to the port

103 ;;Quote: on a full port, a task can suspend, error, or post one message for future transmission with acknowledgment

103 ;;Quote: Mach sends a large message as copy-on-write data via a temporary kernel address map