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Escape sequences are used in the programming languages C and C++, and their design was copied in many other languages such as Java and C#. An escape sequence is a sequence of characters that does not represent itself when used inside a character or string literal, but is translated into another character or a sequence of characters that may be difficult or impossible to represent directly.

In C, all escape sequences consist of two or more characters, the first of which is the backslash, (called the 'Escape character'); the remaining characters determine the interpretation of the escape sequence. For example, n is an escape sequence that denotes a newline character.

Orwell Dev-C is a full-featured Integrated Development Environment (IDE) for the C/C programming language. It uses Mingw port of GCC (GNU Compiler Collection) as its compiler. You want to enter actual costs, but you find out that you can’t do that. That’s because Project automatically calculates actual costs based on the actual work accumulated or materials consumed on tasks. You can enter actual costs on assigned tasks that have been completed (remaining work is zero) in any view that has a cost table applied.

Motivation[edit]

Suppose we want to print out Hello, on one line, followed by world! on the next line. One could attempt to represent the string to be printed as a single literal as follows:

This is not valid in C, since a string literal may not span multiple logical source lines. This can be worked around by printing the newline character using its numerical value (0x0A in ASCII),

This instructs the program to print Hello,, followed by the byte whose numerical value is 0x0A, followed by world!. While this will indeed work when the machine uses the ASCII encoding, it will not work on systems that use other encodings, that have a different numerical value for the newline character. It is also not a good solution because it still does not allow to represent a newline character inside a literal, and instead takes advantage of the semantics of printf. In order to solve these problems and ensure maximum portability between systems, C interprets n inside a literal as a newline character, whatever that may be on the target system:

In this code, the escape sequencen does not stand for a backslash followed by the letter n, because the backslash causes an 'escape' from the normal way characters are interpreted by the compiler. After seeing the backslash, the compiler expects another character to complete the escape sequence, and then translates the escape sequence into the bytes it is intended to represent. Thus, 'Hello,nworld!' represents a string with an embedded newline, regardless of whether it is used inside printf or anywhere else.

This raises the issue of how to represent an actual backslash inside a literal. This is done by using the escape sequence , as seen in the next section.

Some languages don't have escape sequences, for example Pascal. Instead a command including a newline would be used (writeln includes a newline, write excludes it).

Table of escape sequences[edit]

The following escape sequences are defined in standard C. This table also shows the values they map to in ASCII. However, these escape sequences can be used on any system with a C compiler, and may map to different values if the system does not use a character encoding based on ASCII.

Note 1.^ Common non-standard code; see the Notes section below.

Note 2.^ There may be one, two, or three octal numerals n present; see the Notes section below.

Note 3.^ u takes 4 hexadecimal digits h; see the Notes section below.

Note 4.^ U takes 8 hexadecimal digits h; see the Notes section below.

Notes[edit]

n produces one byte, despite the fact that the platform may use more than one byte to denote a newline, such as the DOS/Windows CR-LF sequence, 0x0D 0x0A. The translation from 0x0A to 0x0D 0x0A on DOS and Windows occurs when the byte is written out to a file or to the console, and the inverse translation is done when text files are read.

A hex escape sequence must have at least one hex digit following x, with no upper bound; it continues for as many hex digits as there are. Thus, for example, xABCDEFG denotes the byte with the numerical value ABCDEF₁₆, followed by the letter G, which is not a hex digit. However, if the resulting integer value is too large to fit in a single byte, the actual numerical value assigned is implementation-defined. Most platforms have 8-bit char types, which limits a useful hex escape sequence to two hex digits. However, hex escape sequences longer than two hex digits might be useful inside a wide character or wide string literal(prefixed with L):

An octal escape sequence consists of followed by one, two, or three octal digits. The octal escape sequence ends when it either contains three octal digits already, or the next character is not an octal digit. For example, 11 is a single octal escape sequence denoting a byte with numerical value 9 (11 in octal), rather than the escape sequence 1 followed by the digit 1. However, 1111 is the octal escape sequence 111 followed by the digit 1. In order to denote the byte with numerical value 1, followed by the digit 1, one could use '1'1', since C automatically concatenates adjacent string literals. Note that some three-digit octal escape sequences may be too large to fit in a single byte; this results in an implementation-defined value for the byte actually produced. The escape sequence 0 is a commonly used octal escape sequence, which denotes the null character, with value zero.

Non-standard escape sequences[edit]

A sequence such as z is not a valid escape sequence according to the C standard as it is not found in the table above. The C standard requires such 'invalid' escape sequences to be diagnosed (i.e., the compiler must print an error message). Notwithstanding this fact, some compilers may define additional escape sequences, with implementation-defined semantics. An example is the e escape sequence, which has 1B as the hexadecimal value in ASCII, represents the escape character, and is supported in GCC,^[2]clang and tcc. It wasn't however added to the C standard repertoire, because it has no meaningful equivalent in some character sets (such as EBCDIC).^[1]

Universal character names[edit]

From the C99 standard, C has also supported escape sequences that denote Unicode code points in string literals. Such escape sequences are called universal character names, and have the form uhhhh or Uhhhhhhhh, where h stands for a hex digit. Unlike the other escape sequences considered, a universal character name may expand into more than one code unit.

The sequence uhhhh denotes the code pointhhhh, interpreted as a hexadecimal number. The sequence Uhhhhhhhh denotes the code point hhhhhhhh, interpreted as a hexadecimal number. (Therefore, code points located at U+10000 or higher must be denoted with the U syntax, whereas lower code points may use u or U.) The code point is converted into a sequence of code units in the encoding of the destination type on the target system. For example, consider

The string s1 will contain a single byte (not counting the terminating null) whose numerical value, the actual value stored in memory, is in fact 0xC0. The string s2 will contain the character 'Á', U+00C1 LATIN CAPITAL LETTER A WITH ACUTE. On a system that uses the UTF-8 encoding, the string s2 will contain two bytes, 0xC3 0xA1. The string s3 contains a single wchar_t, again with numerical value 0xC0. The string s4 contains the character 'À' encoded into wchar_t, if the UTF-16 encoding is used, then s4 will also contain only a single wchar_t, 16 bits long, with numerical value 0x00C0. A universal character name such as U0001F603 may be represented by a single wchar_t if the UTF-32 encoding is used, or two if UTF-16 is used.

Importantly, the universal character name u00C0 always denotes the character 'À', regardless of what kind of string literal it is used in, or the encoding in use. Again, U0001F603 always denotes the character at code point 1F603₁₆, regardless of context. On the other hand, octal and hex escape sequences always denote certain sequences of numerical values, regardless of encoding. Therefore, universal character names are complementary to octal and hex escape sequences; while octal and hex escape sequences represent 'physical' code units, universal character names represent code points, which may be thought of as 'logical' characters.

See also[edit]

References[edit]

1. ^ ^ab'Rationale for International Standard - Programming Languages - C'(PDF). 5.10. April 2003. Archived(PDF) from the original on 2016-06-06. Retrieved 2010-10-17.
2. ^'6.35 The Character <ESC> in Constants'. GCC 4.8.2 Manual. Archived from the original on 2019-05-12. Retrieved 2014-03-08.

Further reading[edit]

• ISO/IEC 9899:1999, Programming languages — C
• Kernighan, Brian W.; Ritchie, Dennis M. (2003) [1988]. The C Programming Language (2 ed.). Prentice Hall. ISBN978-0-13308621-8.
• Lafore, Robert (2001). Object-Oriented Programming in Turbo C++ (1 ed.). Galgotia Publications. ISBN978-8-18562322-1.

This walkthrough shows how to create a traditional Windows desktop application in Visual Studio. The example application you'll create uses the Windows API to display 'Hello, Windows desktop!' in a window. You can use the code that you develop in this walkthrough as a pattern to create other Windows desktop applications.

The Windows API (also known as the Win32 API, Windows Desktop API, and Windows Classic API) is a C-language-based framework for creating Windows applications. It has been in existence since the 1980s and has been used to create Windows applications for decades. More advanced and easier-to-program frameworks have been built on top of the Windows API. For example, MFC, ATL, the .NET frameworks. Even the most modern Windows Runtime code for UWP and Store apps written in C++/WinRT uses the Windows API underneath. For more information about the Windows API, see Windows API Index. There are many ways to create Windows applications, but the process above was the first.

Important

For the sake of brevity, some code statements are omitted in the text. The Build the code section at the end of this document shows the complete code.

Prerequisites

Dev C++ For Windows 10

• A computer that runs Microsoft Windows 7 or later versions. We recommend Windows 10 for the best development experience.

• A copy of Visual Studio. For information on how to download and install Visual Studio, see Install Visual Studio. When you run the installer, make sure that the Desktop development with C++ workload is checked. Don't worry if you didn't install this workload when you installed Visual Studio. You can run the installer again and install it now.

• An understanding of the basics of using the Visual Studio IDE. If you've used Windows desktop apps before, you can probably keep up. For an introduction, see Visual Studio IDE feature tour.

• An understanding of enough of the fundamentals of the C++ language to follow along. Don't worry, we don't do anything too complicated.

Create a Windows desktop project

Follow these steps to create your first Windows desktop project. As you go, you'll enter the code for a working Windows desktop application. To see the documentation for your preferred version of Visual Studio, use the Version selector control. It's found at the top of the table of contents on this page.

To create a Windows desktop project in Visual Studio 2019

1. From the main menu, choose File > New > Project to open the Create a New Project dialog box.

2. At the top of the dialog, set Language to C++, set Platform to Windows, and set Project type to Desktop.

3. From the filtered list of project types, choose Windows Desktop Wizard then choose Next. In the next page, enter a name for the project, for example, DesktopApp.

4. Choose the Create button to create the project.

5. The Windows Desktop Project dialog now appears. Under Application type, select Desktop application (.exe). Under Additional options, select Empty project. Choose OK to create the project.

6. In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.

7. In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor. To continue, skip ahead to Create the code.

To create a Windows desktop project in Visual Studio 2017

1. On the File menu, choose New and then choose Project.

2. In the New Project dialog box, in the left pane, expand Installed > Visual C++, then select Windows Desktop. In the middle pane, select Windows Desktop Wizard.

   In the Name box, type a name for the project, for example, DesktopApp. Choose OK.

3. In the Windows Desktop Project dialog, under Application type, select Windows application (.exe). Under Additional options, select Empty project. Make sure Precompiled Header isn't selected. Choose OK to create the project.

4. In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.

5. In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor. To continue, skip ahead to Create the code.

To create a Windows desktop project in Visual Studio 2015

1. On the File menu, choose New and then choose Project.

2. In the New Project dialog box, in the left pane, expand Installed > Templates > Visual C++, and then select Win32. In the middle pane, select Win32 Project.

   In the Name box, type a name for the project, for example, DesktopApp. Choose OK.

3. On the Overview page of the Win32 Application Wizard, choose Next.

4. On the Application Settings page, under Application type, select Windows application. Under Additional options, uncheck Precompiled header, then select Empty project. Choose Finish to create the project.

5. In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.

6. In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor.

Create the code

Next, you'll learn how to create the code for a Windows desktop application in Visual Studio.

To start a Windows desktop application

1. Just as every C application and C++ application must have a main function as its starting point, every Windows desktop application must have a WinMain function. WinMain has the following syntax.

   For information about the parameters and return value of this function, see WinMain entry point.

   Note

   What are all those extra words, such as CALLBACK, or HINSTANCE, or _In_? The traditional Windows API uses typedefs and preprocessor macros extensively to abstract away some of the details of types and platform-specific code, such as calling conventions, __declspec declarations, and compiler pragmas. In Visual Studio, you can use the IntelliSense Quick Info feature to see what these typedefs and macros define. Hover your mouse over the word of interest, or select it and press Ctrl+K, Ctrl+I for a small pop-up window that contains the definition. For more information, see Using IntelliSense. Parameters and return types often use SAL Annotations to help you catch programming errors. For more information, see Using SAL Annotations to Reduce C/C++ Code Defects.

2. Windows desktop programs require <windows.h>. <tchar.h> defines the TCHAR macro, which resolves ultimately to wchar_t if the UNICODE symbol is defined in your project, otherwise it resolves to char. If you always build with UNICODE enabled, you don't need TCHAR and can just use wchar_t directly.

3. Along with the WinMain/barbie-cooking-games-dress-up-games-free-download.html. function, every Windows desktop application must also have a window-procedure function. This function is typically named WndProc, but you can name it whatever you like. WndProc has the following syntax.

   In this function, you write code to handle messages that the application receives from Windows when events occur. For example, if a user chooses an OK button in your application, Windows will send a message to you and you can write code inside your WndProc function that does whatever work is appropriate. It's called handling an event. You only handle the events that are relevant for your application.

   For more information, see Window Procedures.

To add functionality to the WinMain function

1. In the WinMain function, you populate a structure of type WNDCLASSEX. The structure contains information about the window: the application icon, the background color of the window, the name to display in the title bar, among other things. Importantly, it contains a function pointer to your window procedure. The following example shows a typical WNDCLASSEX structure.

   For information about the fields of the structure above, see WNDCLASSEX.

2. Register the WNDCLASSEX with Windows so that it knows about your window and how to send messages to it. Use the RegisterClassEx function and pass the window class structure as an argument. The _T macro is used because we use the TCHAR type.

3. Now you can create a window. Use the CreateWindow function.

   This function returns an HWND, which is a handle to a window. A handle is somewhat like a pointer that Windows uses to keep track of open windows. For more information, see Windows Data Types.

4. At this point, the window has been created, but we still need to tell Windows to make it visible. That's what this code does:

   The displayed window doesn't have much content because you haven't yet implemented the WndProc function. In other words, the application isn't yet handling the messages that Windows is now sending to it.

5. To handle the messages, we first add a message loop to listen for the messages that Windows sends. When the application receives a message, this loop dispatches it to your WndProc function to be handled. The message loop resembles the following code.

   For more information about the structures and functions in the message loop, see MSG, GetMessage, TranslateMessage, and DispatchMessage.

   At this point, the WinMain function should resemble the following code.

To add functionality to the WndProc function

1. To enable the WndProc function to handle the messages that the application receives, implement a switch statement.

   One important message to handle is the WM_PAINT message. The application receives the WM_PAINT message when part of its displayed window must be updated. The event can occur when a user moves a window in front of your window, then moves it away again. Your application doesn't know when these events occur. Only Windows knows, so it notifies your app with a WM_PAINT message. When the window is first displayed, all of it must be updated.

   To handle a WM_PAINT message, first call BeginPaint, then handle all the logic to lay out the text, buttons, and other controls in the window, and then call EndPaint. For the application, the logic between the beginning call and the ending call is to display the string 'Hello, Windows desktop!' in the window. In the following code, notice that the TextOut function is used to display the string.

   HDC in the code is a handle to a device context, which is a data structure that Windows uses to enable your application to communicate with the graphics subsystem. The BeginPaint and EndPaint functions make your application behave like a good citizen and doesn't use the device context for longer than it needs to. The functions help make the graphics subsystem is available for use by other applications.

2. An application typically handles many other messages. For example, WM_CREATE when a window is first created, and WM_DESTROY when the window is closed. The following code shows a basic but complete WndProc function.

Build the code

As promised, here's the complete code for the working application.

To build this example

1. Delete any code you've entered in HelloWindowsDesktop.cpp in the editor. Copy this example code and then paste it into HelloWindowsDesktop.cpp:

2. On the Build menu, choose Build Solution. The results of the compilation should appear in the Output window in Visual Studio.

3. To run the application, press F5. A window that contains the text 'Hello, Windows desktop!' should appear in the upper-left corner of the display.

Congratulations! You've completed this walkthrough and built a traditional Windows desktop application.

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See also