• C++ Input And Output
• C++ Input File Example
• C Input From File

File Input/Output in C. A file represents a sequence of bytes on the disk where a group of related data is stored. File is created for permanent storage of data. It is a ready made structure. In C language, we use a structure pointer of file type to declare a file.

C++ Syntax

Let's break up the following code to understand it better:

Example

• To perform input and output, a C program: Construct a stream object. Connect (Associate) the stream object to an actual IO device (e.g., keyboard, console, file, network, another program). Perform input/output operations on the stream, via the functions defined in the stream's pubic interface in a device independent manner.
• You are attempting to redirect the contents of a file to program.exe using file.txt. This is not a command line argument. It simply redirects the contents of the file to the standard input of your program. To get those contents you will need to extract from std::cin.

Example explained

Line 1:#include <iostream> is a header file library that lets us work with input and output objects, such as cout (used in line 5). Header files add functionality to C++ programs.

Line 2:using namespace std means that we can use names for objects and variables from the standard library.

Don't worry if you don't understand how #include <iostream> and using namespace std works. Just think of it as something that (almost) always appears in your program.

Line 3: A blank line. C++ ignores white space.

Line 4: Another thing that always appear in a C++ program, is int main(). This is called a function. Any code inside its curly brackets {} will be executed.

The options in the Edit menu allow you to perform other tasks, such as Fades, transitions, normalization, export and more.Why Serum?The dream synthesizer did not seem to exist: a wavetable synthesizer with real high-quality sound, a visual and creative interface based on the to create and emit fun sounds instead of boring, and the ability to create / import depth / modify/modify wavetables and manipulate them during playback in real time. Serum plugin free crack.

Line 5:cout (pronounced 'see-out') is an object used together with the insertion operator (<<) to output/print text. In our example it will output 'Hello World'.

Note: Every C++ statement ends with a semicolon ;.

Note: The body of int main() could also been written as:
int main () { cout << 'Hello World! '; return 0; }

Remember: The compiler ignores white spaces. However, multiple lines makes the code more readable.

Line 6:return 0 ends the main function.

Line 7: Do not forget to add the closing curly bracket } to actually end the main function.

Omitting Namespace

You might see some C++ programs that runs without the standard namespace library. The using namespace std line can be omitted and replaced with the std keyword, followed by the :: operator for some objects:

Example

It is up to you if you want to include the standard namespace library or not.

In the C++programming language, input/output library refers to a family of class templates and supporting functions in the C++ Standard Library that implement stream-based input/output capabilities.^[1][2] It is an object-oriented alternative to C's FILE-based streams from the C standard library.^[3][4]

History[edit]

Bjarne Stroustrup, the creator of C++, wrote the first version of the stream I/O library in 1984, as a type-safe and extensible alternative to C's I/O library.^[5] The library has undergone a number of enhancements since this early version, including the introduction of manipulators to control formatting, and templatization to allow its use with character types other than char.

Standardization in 1998 saw the library moved into the std namespace, and the main header changed from <iostream.h> to <iostream>. It is this standardized version that is covered in the rest of the article.

Overview[edit]

Most of the classes in the library are actually very generalized class templates. Each template can operate on various character types, and even the operations themselves, such as how two characters are compared for equality, can be customized. However, the majority of code needs to do input and output operations using only one or two character types, thus most of the time the functionality is accessed through several typedefs, which specify names for commonly used combinations of template and character type.

For example, basic_fstream<CharT,Traits> refers to the generic class template that implements input/output operations on file streams. It is usually used as fstream which is an alias for basic_fstream<char,char_traits<char>>, or, in other words, basic_fstream working on characters of type char with the default character operation set.

The classes in the library could be divided into roughly two categories: abstractions and implementations. Classes, that fall into abstractions category, provide an interface which is sufficient for working with any type of a stream. The code using such classes doesn't depend on the exact location the data is read from or is written to. For example, such code could write data to a file, a memory buffer or a web socket without a recompilation. The implementation classes inherit the abstraction classes and provide an implementation for concrete type of data source or sink. The library provides implementations only for file-based streams and memory buffer-based streams.

The classes in the library could also be divided into two groups by whether it implements low-level or high-level operations. The classes that deal with low-level stuff are called stream buffers. They operate on characters without providing any formatting functionality. These classes are very rarely used directly. The high-level classes are called streams and provide various formatting capabilities. They are built on top of stream buffers.

The following table lists and categorizes all classes provided by the input-output library.

Header files[edit]

The classes of the input/output library reside in several headers.

• <ios> contains the definitions of ios_base and basic_ios classes, that manage formatting information and the associated stream-buffer.
• <istream> contains the definition of basic_istream class template, which implements formatted input.
• <ostream> contains the definition of basic_ostream class template, which implements formatted output.
• <iostream> contains the definition of basic_iostream class template, which implements formatted input and output, and includes <ios>, <istream> and <ostream>.
• <fstream> contains the definitions of basic_ifstream, basic_ofstream and basic_fstream class templates which implement formatted input, output and input/output on file streams.
• <sstream> contains the definitions of basic_istringstream, basic_ostringstream and basic_stringstream class templates which implement formatted input, output and input/output on string-based streams.
• <iomanip> contains formatting manipulators.
• <iosfwd> contains forward declarations of all classes in the input/output library.

Stream buffers[edit]

There are twelve stream buffer classes defined in the C++ language as the table.

Support classes[edit]

ios_base and basic_ios are two classes that manage the lower-level bits of a stream. ios_base stores formatting information and the state of the stream. basic_ios manages the associated stream-buffer. basic_ios is commonly known as simply ios or wios, which are two typedefs for basic_ios with a specific character type. basic_ios and ios_base are very rarely used directly by programmers. Usually, their functionality is accessed through other classes such as iostream which inherit them.^[6][7]

Typedefs[edit]

Formatting manipulators[edit]

Input/output streams[edit]

C++input/output streams are primarily defined by iostream, a header file that is part of the C++ standard library (the name stands for Input/Output Stream). In C++ and its predecessor, the C programming language, there is no special syntax for streaming data input or output. Instead, these are combined as a library of functions. Like the cstdio header inherited from C's stdio.h, iostream provides basic input and output services for C++ programs. iostream uses the objectscin, cout, cerr, and clog for sending data to and from the standard streams input, output, error (unbuffered), and log (buffered) respectively. As part of the C++ standard library, these objects are a part of the stdnamespace.^[8]

The cout object is of type ostream, which overloads the left bit-shiftoperator to make it perform an operation completely unrelated to bitwise operations, and notably evaluate to the value of the left argument, allowing multiple operations on the same ostream object, essentially as a different syntax for method cascading, exposing a fluent interface. The cerr and clog objects are also of type ostream, so they overload that operator as well. The cin object is of type istream, which overloads the right bit-shift operator. The directions of the bit-shift operators make it seem as though data is flowing towards the output stream or flowing away from the input stream.

Output formatting[edit]

Methods[edit]

Manipulators[edit]

Manipulators are objects that can modify a stream using the << or >> operators.

Other manipulators can be found using the header iomanip.

Criticism[edit]

Some environments do not provide a shared implementation of the C++ library. These include embedded systems and Windows systems running programs built with MinGW. Under these systems, the C++ standard library must be statically linked to a program, which increases the size of the program,^[9] or distributed as a shared library alongside the program.Some implementations of the C++ standard library have significant amounts of dead code. For example, GNU libstdc++ automatically constructs a locale when building an ostream even if a program never uses any types (date, time or money) that a locale affects,^[10]and a statically linked 'Hello, World!' program that uses <iostream> of GNU libstdc++ produces an executable an order of magnitude larger than an equivalent program that uses <cstdio>.^[11]

C++ Input And Output

There exist partial implementations of the C++ standard library designed for space-constrained environments; their <iostream> may leave out features that programs in such environments may not need, such as locale support.^[12]

Naming conventions[edit]

Examples[edit]

The canonical 'Hello, World!' program can be expressed as follows:

This program would output 'Hello, world!' followed by a newline and standard output stream buffer flush.

The following example creates a file called 'file.txt' and puts the text 'Hello, world!' followed by a newline into it.

C++ Input File Example

References[edit]

1. ^ISO/IEC 14882:2003 Programming Languages — C++. [lib.string.streams]/1
2. ^Stanley B. Lippman, Josee Lajoie (1999). C++ Primer (third ed.). Massachusetts: Addison-Wesley. pp. 1109–1112. ISBN0-201-82470-1.
3. ^Bjarne Stroustrup (1997). The C++ programming language (third ed.). Addison-Wesley. pp. 637–640. ISBN0-201-88954-4.
4. ^Stanley B. Lippman, Josee Lajoie (1999). C++ Primer (third ed.). Massachusetts: Addison-Wesley. pp. 1063–1067. ISBN0-201-82470-1.
5. ^Bjarne Stroustrup. 'A History of C++: 1979–1991'(PDF).
6. ^Stanley B. Lippman, Josee Lajoie (1999). C++ Primer (third ed.). Massachusetts: Addison-Wesley. pp. 1112–1120. ISBN0-201-82470-1.
7. ^'<ios> Visual Studio 2010'. Microsoft MSDN: Visual Studio 2010. Retrieved 28 September 2011.
8. ^Holzner, Steven (2001). C++ : Black Book. Scottsdale, Ariz.: Coriolis Group. p. 584. ISBN1-57610-777-9. ..endl, which flushes the output buffer and sends a newline to the standard output stream.
9. ^'MinGW.org: Large executables'. Retrieved 22 April 2009.
10. ^GNU libstdc++ source code, bits/ios_base.h
11. ^C++ vs. C - Pin Eight
12. ^'uClibc++ C++ library'. Retrieved 6 January 2012.

C Input From File

External links[edit]