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C H A P T E R 1
Overview
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System Services
The system performs automatic memory management of the NewtonScript heap.
You don't need to worry about memory allocation or disposal in an application.
The system automatically allocates memory when you create a new object in
NewtonScript. When references to an object no longer exist, it is freed during the
next garbage collection cycle. The system performs garbage collection
automatically when it needs additional memory.
The Newton operating system optimizes use of memory by using compression.
Various parts of memory are compressed and decompressed dynamically and
transparently, as needed. This occurs at a low level, and applications don't need to
be concerned with these operations.
Packages
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A package is the unit in which software is installed on and removed from the
Newton. Packages can combine multiple pieces of software into a single unit. The
operating system manages packages, which can be installed from PCMCIA cards,
from a serial connection to a desktop computer, a network connection, or via
modem. When a package comes into the Newton system, the system automatically
opens it and dispatches its parts to appropriate handlers in the system.
A package consists of a header, which contains the package name and other
information, and one or more parts, which contain the software. Parts can include
applications, communication drivers, fonts, and system updates (system software
code loaded into RAM that overrides or extends the built-in ROM code). A
package can also export objects for use by other packages in the system, and can
import (use) objects that are exported by other packages.
Packages are optionally stored compressed on the Newton. Compressed packages
occupy much less space (roughly half of their uncompressed size), but applications
in compressed packages may execute somewhat slower and use slightly more
battery power, because of the extra work required to decompress them when they
are executed.
For more information about packages, refer to Chapter 11, "Data Storage and
Retrieval."
System Services
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The Newton system software contains hundreds of routines organized into
functional groups of services. Your application can use these routines to accomplish
specific tasks such as opening and closing views, storing and retrieving data,
playing sounds, drawing shapes, and so on. This section includes brief descriptions
of the more important system services with which your application will need to
interact. Note that communications services are described in a separate section
following this one.
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