Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 509)

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CHAPTER 12

Special-Purpose Objects for Data Storage and Retrieval

About Special-Purpose Storage Objects 12-3

Normal binary objects encapsulate their data and reside entirely in the NewtonScript

heap; thus, creating one of these objects or reading any of its data requires an

amount of heap space sufﬁcient to hold all its data. Therefore, the size of a normal

binary object is limited by the amount of NewtonScript heap space available at the

time it is created. For example, a binary object encapsulating 5 KB of data requires

5 KB of NewtonScript heap space. If sufﬁcient heap space is not available, the

binary object cannot be created.

In contrast, VBO data resides on a store speciﬁed when the VBO is created. The

system manages VBO data automatically, providing NewtonScript objects with

transparent access to it on demand. A VBO can hold more data than a normal

binary object because it is not limited by the amount of free space available in the

NewtonScript heap. Contrasting the previous example, a VBO holding 5 KB of

data requires a negligible amount of heap space, because its data resides in store

memory, rather than in the NewtonScript heap.

Note

The system does not allocate store memory for VBO data until it

is needed to write data to the store. Testing the amount of store

memory available when the VBO is created does not guarantee

the future availability of this memory. Thus, it is possible to fail

due to lack of store space when writing to a VBO, even though the

VBO was created successfully. The only practical solution to this

problem is to enclose in a

try block any code that writes VBO

data.

◆

Parts 12

Recall that a package is the basic unit of downloadable Newton software: it

provides a means of loading code, resources, objects, and scripts into a Newton

device. A package consists of one or more constituent units called parts.

The format of a part is identiﬁed by a four-character identiﬁer called its type or

its part code. Table 12-1 on page 12-4 lists the various kinds of parts and their

associated

type identiﬁers.

Some of the parts described in Table 12-1 may already be familiar to you.

Form

parts are the Newton application packages you create with Newton Toolkit.

Book

parts are the interactive digital books described in the

Newton Book Maker User’s

Guide. Store parts (parts of type soup) are useful for the storage of read-only data

and are discussed later in this chapter. Dictionary parts (parts of type

dict)

supplement the built-in word lists used by the recognition subsystem.

Font parts

are used to add new typefaces to Newton devices; for more information about these

parts, contact Newton Developer Technical Support.

Auto parts are described in

the Newton Toolkit User’s Guide.

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