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The formatting placeholders in scanf are more or less the same as that in printf, its reverse function.As in printf, the POSIX extension n$ is defined. [2]There are rarely constants (i.e., characters that are not formatting placeholders) in a format string, mainly because a program is usually not designed to read known data, although scanf does accept these if explicitly specified.
As the format string is processed left-to-right, a subsequent value is used for each format specifier found. A format specifier starts with a % character and has one or more following characters that specify how to serialize a value. The format string syntax and semantics is the same for all of the functions in the printf-like family.
Since the C99 standard, C supports escape sequences that denote Unicode code points, called universal character names. They have the form \u hhhh or \U hhhhhhhh , where h stands for a hex digit. Unlike other escape sequences, a universal character name may expand into more than one code unit.
The C programming language provides many standard library functions for file input and output.These functions make up the bulk of the C standard library header <stdio.h>. [1] The functionality descends from a "portable I/O package" written by Mike Lesk at Bell Labs in the early 1970s, [2] and officially became part of the Unix operating system in Version 7.
Strings are passed to functions by passing a pointer to the first code unit. Since char * and wchar_t * are different types, the functions that process wide strings are different than the ones processing normal strings and have different names. String literals ("text" in the C source code) are converted to arrays during compilation. [2]
In contrast, a character entity reference refers to a character by the name of an entity which has the desired character as its replacement text. The entity must either be predefined (built into the markup language) or explicitly declared in a Document Type Definition (DTD). The format is the same as for any entity reference: &name;
[10] [11] However it still contains errors such as defining an array of char as a character array (rather than a byte array). [12] Unicode can also be stored in strings made up of code units that are larger than char. These are called "wide characters". The original C type was called wchar_t.
In computer programming, a null-terminated string is a character string stored as an array containing the characters and terminated with a null character (a character with an internal value of zero, called "NUL" in this article, not same as the glyph zero).