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Null Objects. The null object, if actually written to a file, is simply the four characters null. It is synonymous with a missing value, which is why it’s extremely rare to see one in a PDF. If you have reason to work with the null value, be sure to consult ISO 32000 carefully about the subtleties involving its handling. Boolean Objects.
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12 cze 2018 · What is the meaning of null? How is null implemented? When should you use null in your source code, and when should you not use it? Introduction. null is a fundamental concept in many programming languages. It is ubiquitous in all kinds of source code written in these languages.
4 paź 2016 · In practice, the textual nature of PDF means that bytes are grouped into several character classes: white-space , to separate tokens : 0x00 (null), 0x09 (horizontal tab), 0x0A (line feed), 0x0C (form feed), 0x0D (carriage return), 0x20 (space);
NULL is a macro, defined in as a null pointer constant. \0 is a construction used to represent the null character, used to terminate a string. A null character is a byte which has all its bits set to 0.
Introduction. Many programming languages support a distinguished null or nil value for pointer or reference types to indicate that a pointer or reference currently does not refer to any object. Examples include NIL in Pascal [4], Modula-2 [10], and Oberon(-2) [11], 0 (when used as a pointer value) in C and C++ [8], and null in Java [3].
This inability to explicitly express a null or missing value raises several questions when defining the semantics of a programming language, e. g., whether it is allowed and well-defined to use uninitialized variables or to omit explicit return statements in functions.
In all modern character sets, the null character has a code point value of zero. In most encodings, this is translated to a single code unit with a zero value. For instance, in UTF-8 it is a single zero byte. However, in Modified UTF-8 the null character is encoded as two bytes: 0xC0,0x80.
