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C H A P T E R 1
Overview
Operating System
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Another operating system task of interest is the Inker. The Inker task is responsible
for gathering and displaying input from the electronic tablet overlaying the screen
when the user writes on the Newton. The Inker exists as a separate task so that the
Newton can gather input and display electronic ink at the same time as other
operations are occurring.
All Newton applications, including the recognition system, built-in applications,
and applications you develop, run in a single operating system task, called the
Application task.
NewtonScript applications have no direct access to the operating system level of
software. Access to certain low-level resources, such as communications, is
provided by higher-level interfaces.
Memory
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It is helpful to understand the use of random access memory (RAM) in the system,
since this resource is shared by the operating system and all applications. Newton
RAM is divided into separate domains, or sections, that have controlled access.
Each domain has its own heap and stack. It is important to know about three of
these domains:
The operating system domain. This portion of memory is reserved for use by the
operating system. Only operating system tasks have access to this domain.
The storage domain. This portion of memory is reserved for permanent,
protected storage of user data. All soups, which store the data, reside here, as
well as any packages that have been downloaded into the Newton. To protect the
data in the storage domain from inadvertent damage, it can only be accessed
through the object storage system interface, described in Chapter 11, "Data
Storage and Retrieval." If the user adds a PCMCIA card containing RAM, Flash
RAM, or read-only memory (ROM) devices, the memory on the card is used to
extend the size of the storage domain.
The storage domain occupies special persistent memory; that is, this memory is
maintained even during a system reset. This protects user data, system software
updates, and downloaded packages from being lost during system resets. The
used and free space in the storage domain is reported to the user in the Memory
Info slip in the Extras Drawer.
The application domain. This portion of memory is used for dynamic memory
allocation by the handwriting recognizers and all Newton applications. A fixed
part of this domain is allocated to the NewtonScript heap. The NewtonScript
heap is important because most objects allocated as a result of your NewtonScript
application code are allocated from the NewtonScript heap. These are the only
memory objects to which you have direct access. The NewtonScript heap is
shared by all applications.
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