In the C programming language, the C Standard Library is a collection of classes and functions, which are written in the core language and part of the C ISO Standard itself. The C Standard Library provides several generic containers, functions to utilize. You can compile C/C programs using makefile. For more details, you can check our 'Makefile Tutorial'. Semicolons and Blocks in C. In C, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity. For example, following are three different statements −. Input/output with files C provides the following classes to perform output and input of characters to/from files: ofstream: Stream class to write on files; ifstream: Stream class to read from files; fstream: Stream class to both read and write from/to files.; These classes are derived directly or indirectly from the classes istream and ostream.We have already used objects whose types were. Lecturer You're probably wondering,so what are the parts required for a C program?We will learn how to structure a C programby exploring a program called Hello, World.I'm already inside my Dev-C IDE.I'm going to create a new project.I'm going to go to file, new, and I'm going to click on project.Notice under the new project, under the tab basic,I can choose to. Structure of a program The best way to learn a programming language is by writing programs. Typically, the first program beginners write is a program called 'Hello World', which simply prints 'Hello World' to your computer screen. Although it is very simple, it contains all the fundamental components C.
- Parts And Function Of Dev C++
- Dev C++ Download And Install
- Parts Of Dev C 2017
- Dev C++ Download For Laptop
- Dev C++ 5.11
- Dev C++ Program Download
C++ Standard Library |
---|
Containers |
C standard library |
|
In the C++ programming language, the C++ Standard Library is a collection of classes and functions, which are written in the core language and part of the C++ ISO Standard itself.[1]
Parts And Function Of Dev C++
Overview[edit]
The C++ Standard Library provides several generic containers, functions to utilize and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for everyday tasks such as finding the square root of a number. The C++ Standard Library also incorporates 18 headers of the ISO C90C standard library ending with '.h', but their use is deprecated.[2] No other headers in the C++ Standard Library end in '.h'. Features of the C++ Standard Library are declared within the
std
namespace.The C++ Standard Library is based upon conventions introduced by the Standard Template Library (STL), and has been influenced by research in generic programming and developers of the STL such as Alexander Stepanov and Meng Lee.[3][4] Although the C++ Standard Library and the STL share many features, neither is a strict superset of the other.
A noteworthy feature of the C++ Standard Library is that it not only specifies the syntax and semantics of generic algorithms, but also places requirements on their performance.[5] These performance requirements often correspond to a well-known algorithm, which is expected but not required to be used. In most cases this requires linear time O(n) or linearithmic time O(n log n), but in some cases higher bounds are allowed, such as quasilinear time O(n log2n) for stable sort (to allow in-place merge sort). Previously, sorting was only required to take O(n log n) on average, allowing the use of quicksort, which is fast in practice but has poor worst-case performance, but introsort was introduced to allow both fast average performance and optimal worst-case complexity, and as of C++11, sorting is guaranteed to be at worst linearithmic. In other cases requirements remain laxer, such as selection, which is only required to be linear on average (as in quickselect),[6] not requiring worst-case linear as in introselect.
The C++ Standard Library underwent ISO standardization as part of the C++ ISO Standardization effort, and is undergoing further work[7] regarding standardization of expanded functionality.
Implementations[edit]
At CppCon 2019 on September 16th, 2019, Microsoft announced releasing their implementation of the C++ Standard Library (also known as the STL) as open source.[8] It is hosted on GitHub and licensed under the Apache License 2.0 with LLVM Exception.[9][10]
The Apache C++ Standard Library is another open source implementation. It was originally developed commercially by Rogue Wave Software and later donated to the Apache Software Foundation.[11] However, after more than five years without a release, the board of the Apache Software Foundation decided to end this project and move it to Apache Attic.[12]
Standard headers[edit]
The following files contain the declarations of the C++ Standard Library.
Containers[edit]
- <array>
- New in C++11 and TR1. Provides the container class template
std::array
, a container for a fixed sized array. - <bitset>
- Provides the specialized container class
std::bitset
, a bit array. - <deque>
- Provides the container class template
std::deque
, a double-ended queue. - <forward_list>
- New in C++11 and TR1. Provides the container class template
std::forward_list
, a singly linked list. - <list>
- Provides the container class template
std::list
, a doubly linked list. - <map>
- Provides the container class templates
std::map
andstd::multimap
, sorted associative array and multimap. - <queue>
- Provides the container adapter class
std::queue
, a single-ended queue, andstd::priority_queue
, a priority queue. - <set>
- Provides the container class templates
std::set
andstd::multiset
, sorted associative containers or sets. - <stack>
- Provides the container adapter class
std::stack
, a stack. - <unordered_map>
- New in C++11 and TR1. Provides the container class template
std::unordered_map
andstd::unordered_multimap
, hash tables. - <unordered_set>
- New in C++11 and TR1. Provides the container class template
std::unordered_set
andstd::unordered_multiset
. - <vector>
- Provides the container class template
std::vector
, a dynamic array.
General[edit]
- <algorithm>
- Provides definitions of many container algorithms.
- <chrono>
- Provides time elements, such as
std::chrono::duration
,std::chrono::time_point
, and clocks.
- <functional>
- Provides several function objects, designed for use with the standard algorithms.
- <iterator>
- Provides classes and templates for working with iterators.
- <memory>
- Provides facilities for memory management in C++, including the class template
std::unique_ptr
. - <stdexcept>
- Contains standard exception classes such as
std::logic_error
andstd::runtime_error
, both derived fromstd::exception
. - <tuple>
- New in C++11 and TR1. Provides a class template
std::tuple
, a tuple. - <utility>
- Provides the template class
std::pair
, for working with object pairs (two-member tuples), and the namespacestd::rel_ops
, for easier operator overloading.
Localization[edit]
- <locale>
- Defines classes and declares functions that encapsulate and manipulate the information peculiar to a locale.
- <codecvt>
- Provides code conversion facets for various character encodings.
Strings[edit]
- <string>
- Provides the C++ standard string classes and templates.
- <regex>
- New in C++11. Provides utilities for pattern matching strings using regular expressions.
Streams and input/output[edit]
- <fstream>
- Provides facilities for file-based input and output. See fstream.
- <iomanip>
- Provides facilities to manipulate output formatting, such as the base used when formatting integers and the precision of floating point values.
- <ios>
- Provides several types and functions basic to the operation of iostreams.
- <iosfwd>
- Provides forward declarations of several I/O-related class templates.
- <iostream>
- Provides C++ input and output fundamentals. See iostream.
- <istream>
- Provides the template class
std::istream
and other supporting classes for input. - <ostream>
- Provides the template class
std::ostream
and other supporting classes for output. - <sstream>
- Provides the template class
std::stringstream
and other supporting classes for string manipulation. - <streambuf>
- Provides reading and writing functionality to/from certain types of character sequences, such as external files or strings.
Language support[edit]
- <exception>
- Provides several types and functions related to exception handling, including
std::exception
, the base class of all exceptions thrown by the Standard Library. - <limits>
- Provides the template class
std::numeric_limits
, used for describing properties of fundamental numeric types. - <new>
- Provides operators
new
anddelete
and other functions and types composing the fundamentals of C++ memory management. - <typeinfo>
- Provides facilities for working with C++ run-time type information.
Thread support library[edit]
- <thread>
- New in C++11. Provide class and namespace for working with threads.
- <mutex>
- New in C++11. 30.4-1. This section provides mechanisms for mutual exclusion: mutexes, locks, and call once.
- <condition_variable>
- New in C++11. 30.5-1. Condition variables provide synchronization primitives used to block a thread until notified by some other thread that some condition is met or until a system time is reached.
- <future>
- New in C++11. 30.6.1-1. Describes components that a C++ program can use to retrieve in one thread the result (value or exception) from a function that has run in the same thread or another thread.
Numerics library[edit]
Components that C++ programs may use to perform seminumerical operations.
- <complex>
- The header <complex> defines a class template, and numerous functions for representing and manipulating complex numbers.
- <random>
- Facility for generating (pseudo-)random numbers
- <valarray>
- Defines five class templates (valarray, slice_array, gslice_array, mask_array, and indirect_array), two classes (slice and gslice),and a series of related function templates for representing and manipulating arrays of values.
- <numeric>
- Generalized numeric operations.
C standard library[edit]
Each header from the C Standard Library is included in the C++ Standard Library under a different name, generated by removing the .h, and adding a 'c' at the start; for example, 'time.h' becomes 'ctime'. The only difference between these headers and the traditional C Standard Library headers is that where possible the functions should be placed into the std:: namespace. In ISO C, functions in the standard library are allowed to be implemented by macros, which is not allowed by ISO C++.
See also[edit]
References[edit]
- ^ISO/IEC 14882:2003(E) Programming Languages — C++ §17-27
- ^ISO/IEC 14882:2003(E) Programming Languages — C++ §D.5
- ^Bjarne Stroustrup. The Design and Evolution of C++ §8.5. Addison Wesley. ISBN0-201-54330-3.
- ^Alexander Stepanov, Meng Lee (1 August 1994). 'The Standard Template Library'. HP Labs. Retrieved 22 October 2017.
- ^'Generic Algorithms', David Musser
- ^'std::nth_element'. cppreference.com. Retrieved 20 March 2018.
- ^'JTC1/SC22/WG21 - The C++ Standards Committee'. ISO/IEC. Retrieved 7 July 2009.
- ^https://devblogs.microsoft.com/cppblog/open-sourcing-msvcs-stl/
- ^https://github.com/microsoft/STL
- ^https://github.com/microsoft/STL/blob/master/LICENSE.txt
- ^Apache C++ Standard Library
- ^Brett Porter (18 July 2013). 'Apache C++ Standard Library and the Attic'. stdcxx-dev mailing list. Retrieved 27 February 2014.
Further reading[edit]
- Stroustrup, Bjarne. The C++ Programming Language. Addison-Wesley. ISBN978-0321563842.
- Josuttis, Nicolai. The C++ Standard Library - A Tutorial and Reference. Addison-Wesley. ISBN978-0-321-62321-8.
- Van Weert, Peter; Gregoire, Marc. C++ Standard Library Quick Reference. Apress. ISBN978-1484218754.
External links[edit]
- Apache C++ Standard Library Wiki, retired 15 May 2014 (based on Rogue Wave C++ Standard Library 4.1.0)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=C%2B%2B_Standard_Library&oldid=921029183'
C++ provides the following classes to perform output and input of characters to/from files: ofstream
: Stream class to write on filesifstream
: Stream class to read from filesfstream
: Stream class to both read and write from/to files.
These classes are derived directly or indirectly from the classes
istream
and ostream
. We have already used objects whose types were these classes: cin
is an object of class istream
and cout
is an object of class ostream
. Therefore, we have already been using classes that are related to our file streams. And in fact, we can use our file streams the same way we are already used to use cin
and cout
, with the only difference that we have to associate these streams with physical files. Let's see an example:This code creates a file called
example.txt
and inserts a sentence into it in the same way we are used to do with cout
, but using the file stream myfile
instead.But let's go step by step:
Open a file
The first operation generally performed on an object of one of these classes is to associate it to a real file. This procedure is known as to open a file. An open file is represented within a program by a stream (i.e., an object of one of these classes; in the previous example, this was
Dev C++ Download And Install
myfile
) and any input or output operation performed on this stream object will be applied to the physical file associated to it.In order to open a file with a stream object we use its member function
open
:open (filename, mode);
Where
filename
is a string representing the name of the file to be opened, and mode
is an optional parameter with a combination of the following flags:ios::in | Open for input operations. |
ios::out | Open for output operations. |
ios::binary | Open in binary mode. |
ios::ate | Set the initial position at the end of the file. If this flag is not set, the initial position is the beginning of the file. |
ios::app | All output operations are performed at the end of the file, appending the content to the current content of the file. |
ios::trunc | If the file is opened for output operations and it already existed, its previous content is deleted and replaced by the new one. |
All these flags can be combined using the bitwise operator OR (
|
). For example, if we want to open the file example.bin
in binary mode to add data we could do it by the following call to member function open
:Each of the
open
member functions of classes ofstream
, ifstream
and fstream
has a default mode that is used if the file is opened without a second argument:class | default mode parameter |
---|---|
ofstream | ios::out |
ifstream | ios::in |
fstream | ios::in | ios::out |
For
ifstream
and ofstream
classes, ios::in
and ios::out
are automatically and respectively assumed, even if a mode that does not include them is passed as second argument to the open
member function (the flags are combined).For
fstream
, the default value is only applied if the function is called without specifying any value for the mode parameter. If the function is called with any value in that parameter the default mode is overridden, not combined.File streams opened in binary mode perform input and output operations independently of any format considerations. Non-binary files are known as
Parts Of Dev C 2017
text files, and some translations may occur due to formatting of some special characters (like newline and carriage return characters).Since the first task that is performed on a file stream is generally to open a file, these three classes include a constructor that automatically calls the
open
member function and has the exact same parameters as this member. Therefore, we could also have declared the previous myfile
object and conduct the same opening operation in our previous example by writing:Combining object construction and stream opening in a single statement. Both forms to open a file are valid and equivalent.
To check if a file stream was successful opening a file, you can do it by calling to member
is_open
. This member function returns a bool
value of true
in the case that indeed the stream object is associated with an open file, or false
otherwise:Closing a file
When we are finished with our input and output operations on a file we shall close it so that the operating system is notified and its resources become available again. For that, we call the stream's member functionclose
. This member function takes flushes the associated buffers and closes the file:Once this member function is called, the stream object can be re-used to open another file, and the file is available again to be opened by other processes.
In case that an object is destroyed while still associated with an open file, the destructor automatically calls the member function
close
.Text files
Text file streams are those where theios::binary
flag is not included in their opening mode. These files are designed to store text and thus all values that are input or output from/to them can suffer some formatting transformations, which do not necessarily correspond to their literal binary value.Writing operations on text files are performed in the same way we operated with
cout
:Reading from a file can also be performed in the same way that we did with
cin
:This last example reads a text file and prints out its content on the screen. We have created a while loop that reads the file line by line, using getline. The value returned by getline is a reference to the stream object itself, which when evaluated as a boolean expression (as in this while-loop) is
true
if the stream is ready for more operations, and false
if either the end of the file has been reached or if some other error occurred.Checking state flags
The following member functions exist to check for specific states of a stream (all of them return abool
value): bad()
- Returns
true
if a reading or writing operation fails. For example, in the case that we try to write to a file that is not open for writing or if the device where we try to write has no space left. fail()
- Returns
true
in the same cases asbad()
, but also in the case that a format error happens, like when an alphabetical character is extracted when we are trying to read an integer number. eof()
- Returns
true
if a file open for reading has reached the end. good()
- It is the most generic state flag: it returns
false
in the same cases in which calling any of the previous functions would returntrue
. Note thatgood
andbad
are not exact opposites (good
checks more state flags at once).
The member function
clear()
can be used to reset the state flags.get and put stream positioning
All i/o streams objects keep internally -at least- one internal position:ifstream
, like istream
, keeps an internal get position with the location of the element to be read in the next input operation.ofstream
, like
ostream
, keeps an internal put position with the location where the next element has to be written.Finally,
fstream
, keeps both, the get and the put position, like iostream
.These internal stream positions point to the locations within the stream where the next reading or writing operation is performed. These positions can be observed and modified using the following member functions:
tellg() and tellp()
These two member functions with no parameters return a value of the member typestreampos
, which is a type representing the current get position (in the case of tellg
) or the put position (in the case of tellp
).seekg() and seekp()
These functions allow to change the location of the get and put positions. Both functions are overloaded with two different prototypes. The first form is:seekg ( position );
seekp ( position );
Using this prototype, the stream pointer is changed to the absolute position
position
(counting from the beginning of the file). The type for this parameter is streampos
, which is the same type as returned by functions tellg
and tellp
.The other form for these functions is:
seekg ( offset, direction );
seekp ( offset, direction );
Using this prototype, the get or put position is set to an offset value relative to some specific point determined by the parameter
direction
. offset
is of type streamoff
. And direction
is of type seekdir
, which is an enumerated type that determines the point from where offset is counted from, and that can take any of the following values:ios::beg | offset counted from the beginning of the stream |
ios::cur | offset counted from the current position |
ios::end | offset counted from the end of the stream |
The following example uses the member functions we have just seen to obtain the size of a file:
Dev C++ Download For Laptop
Notice the type we have used for variables
begin
and end
:streampos
Dev C++ 5.11
is a specific type used for buffer and file positioning and is the type returned byfile.tellg()
. Values of this type can safely be subtracted from other values of the same type, and can also be converted to an integer type large enough to contain the size of the file.These stream positioning functions use two particular types:
streampos
and streamoff
. These types are also defined as member types of the stream class:Dev C++ Program Download
Type | Member type | Description |
---|---|---|
streampos | ios::pos_type | Defined as fpos<mbstate_t> .It can be converted to/from streamoff and can be added or subtracted values of these types. |
streamoff | ios::off_type | It is an alias of one of the fundamental integral types (such as int or long long ). |
Each of the member types above is an alias of its non-member equivalent (they are the exact same type). It does not matter which one is used. The member types are more generic, because they are the same on all stream objects (even on streams using exotic types of characters), but the non-member types are widely used in existing code for historical reasons.
Binary files
For binary files, reading and writing data with the extraction and insertion operators (<<
and >>
) and functions like getline
is not efficient, since we do not need to format any data and data is likely not formatted in lines.File streams include two member functions specifically designed to read and write binary data sequentially:
write
and read
. The first one (write
) is a member function of ostream
(inherited by ofstream
). And read
is a member function of istream
(inherited by ifstream
). Objects of class fstream
have both. Their prototypes are:write ( memory_block, size );
read ( memory_block, size );
Where
memory_block
is of type char*
(pointer to char
), and represents the address of an array of bytes where the read data elements are stored or from where the data elements to be written are taken. The size
parameter is an integer value that specifies the number of characters to be read or written from/to the memory block.In this example, the entire file is read and stored in a memory block. Let's examine how this is done:
First, the file is open with the
ios::ate
flag, which means that the get pointer will be positioned at the end of the file. This way, when we call to member tellg()
, we will directly obtain the size of the file.Once we have obtained the size of the file, we request the allocation of a memory block large enough to hold the entire file:
Right after that, we proceed to set the get position at the beginning of the file (remember that we opened the file with this pointer at the end), then we read the entire file, and finally close it:
At this point we could operate with the data obtained from the file. But our program simply announces that the content of the file is in memory and then finishes.
Buffers and Synchronization
When we operate with file streams, these are associated to an internal buffer object of typestreambuf
. This buffer object may represent a memory block that acts as an intermediary between the stream and the physical file. For example, with an ofstream
, each time the member function put
(which writes a single character) is called, the character may be inserted in this intermediate buffer instead of being written directly to the physical file with which the stream is associated.The operating system may also define other layers of buffering for reading and writing to files.
When the buffer is flushed, all the data contained in it is written to the physical medium (if it is an output stream). This process is called synchronization and takes place under any of the following circumstances:
- When the file is closed: before closing a file, all buffers that have not yet been flushed are synchronized and all pending data is written or read to the physical medium.
- When the buffer is full: Buffers have a certain size. When the buffer is full it is automatically synchronized.
- Explicitly, with manipulators: When certain manipulators are used on streams, an explicit synchronization takes place. These manipulators are:
flush
andendl
. - Explicitly, with member function sync(): Calling the stream's member function
sync()
causes an immediate synchronization. This function returns anint
value equal to -1 if the stream has no associated buffer or in case of failure. Otherwise (if the stream buffer was successfully synchronized) it returns0
.
Previous: Preprocessor directives | Index |