Windows altında yazılım geliştirme

Abstract

Tez konusunu oluşturan " Windows altında yazılım geliştirme" çalışması 4 ana bölümden oluşmuştur. ilk bölümde Windows altında yazılım geliştirmenin sebepleri tartışılmış, Dos altında geliştirilen uygulamanın Windows altında yazılan aynı uygulama ile kısa bir karşılaştırılması yapılmıştır. ikinci bölümde Windows anlatılmıştır. Windows' un çalışma mantığı MS-DOS 'dan olan farklılıkları, programcıya kazandırdıkları ve OS/2 ile mukayesesini içermektedir. Üçüncü kısımda FoxPro database programının kullanılma sebepleri FoxPro programı ve bu programın DOS ve Windows sürümleri mukayesesini içermektedir. Dördüncü bölümde Windows altında yazılan uygulama anlatılmıştır. Kısa bir süre zarfında değişecek olan işletim sistemlerinde yazılım geliştirmek için Windows altında programlama yapmak büyük önem kazanmaktadır. Bunu sebebi kısa bir zaman sonra yazılacak tüm uygulamalar windows programlamasının mantığında olacaktır.

It started to develop in hardware and especially on software since the computer was first investigated. The people who wrote the programs for the computers started to find out new ways to realize their requirments and started to use all the computer resources. They inserted some new micro chips into the computers, but this improvement has not gone parallel with the micro-chip technology since the micro-chip technology has gone too fast. When the first version of Windows software was first introduced, nobody guessed that it will be a perfect operating system which is able to use all the system resources. In 1990, a new Windows version has been introduced for the hardwares operating with 80386 micro chips. This has been the beginning of the software revolution. This study examines the programming in Windows that can be used in the near future. First of all, DOS and Windows softwares must be compared; Windows has many features that the standart MS-DOS environment does not. For this reason, Windows applications may, at first, seem more complex than the standart MS-DOS applications. This is understandable when you consider some of the additional features that Windows offers: A graphical user interface featuring windows, menus, dialog boxes, and controls for applications Queued input Device-independent graphics Multi-tasking capabilities Data interchange between applications VI When writing applications for the MS-DOS environment, most C programmers use standart C run-time libraries to carry out the _input and output of the applications, memory management, and other activities. The C run-time libraries are for the programmer who is working in a standart operating environment consisting of a character based terminal for user input and output, and exclusive access to system memory as well as to the input and output devices of the computer. In Windows, this charcteristics are no longer valid. Windows aplications share the computer resources, including the CPU, with other applications. Windows applications interact with the user through a graphics- based screen, a keyboard, and a mouse. In a multitasking operating system, it is important to give all aplications some portion of the screen so that the user can interact with all applications. Some systems do this by giving one program full use of the screen while other programs wait the backround. With Windows, every application has access to some part of the screen at all times by means of a window for user interaction. A Window is rectangle that provides a combination of usefull visual devices, such as menus, controls, and scroll bars, with which the user controls an application. In the standart MS-DOS environment, the system automatically prepares the screen for an application- typicaly, by passing a file handle to the aplication. The application, then, can use that file handle to send output to the screen by using conventional C run-time functions or MS-DOS function calls. In Windows, an application must create its own window before performing any output or receiving any input. Once the application creates a window, Windows provides the application with a great deal of information about what the user is doing with the window. Windows automatically performs many of the tasks the user request, such as moving, sizing the window. Another advantage to develop applications in Windows is that, in contrast to a standart C application, which has access to a single screen "surface," a Windows application can create and use any number of overlapping windows to display informations in any number of ways. Windows manages the screen, controls the placement of the display of windows, and ensures that no two applications VII attempt to access the same part of the screen at the same time. In a Windows application, all inputs from the keyboard, mouse, and timer are intercepted by Windows, which places the input in the appropriate applications message queue. When the application is ready to retrieve the input, it simply reads the next input message from its message queue. Windows requires device drivers to convert graphics- output requested to output for a printer, plotter, screen, or another output device. A device driver is a special executable library that an application can load and connect to specific output device and port. A device context represents the device driver, and perhaps the communications port. Your application carries out graphics operations within the contex of a specific device. In Windows memory is a shared resource. Since more than one application can be running at the same time, each application must cooperatively share memory to avoid exhausting the resource. Applications may allocate what they need from system memory. Windows provides two sources of memory: global memory for large applications; and local memory for small applications. To make the most efficient use of memory, Windows often moves or even discards memory objects. This means an application can not "assume" that objects to which it has assigned a memory location remain where they have been put. File input and output in Windows-based applications are similar to file input and output in standart C run time applications. However, there are enough differences between the two systems to make a review of file input and output important. For example although you can use C run-time stream input and output (I/O) functions in Windows it is preferable to use low-level, C run- t ime input and output functions. Also, since Windows is a multi-tasking operating system, you must manage open files carefully. For this reasons, programming in Windows is more efficient than programming in DOS. Users can control all the elements of Windows and can reach all the resources. In fact all the applications run into another program. This program is called Windows. VIII The application which we wrote must check the messages which comes from Windows. However it can do its task. Since an application receives the inputs through its application queue, the chief feature of any Windows application is its message loop. The message loop retrives input messages from the application queue and dispatches them to the appropriate windows. Windows receives keyboard input when the user presses and releases a key. Windows then copies the keyboard input messages from the system queue to the appropriate application queue. The message loop retrieves the keyboard input message, translates them into the Windows character message and dispatches the WM message, as well as the keyboard input messages, to the appropriate window procedure. Windows Figure 1. Collaboration of Windows and Applications IX Windows can receive and distribute input messages for several applications at the same time. Windows collects input messages in its - system queue and then copies each message. After Windows carries out a request to destroy the window, it sends a message directly to the window procedure by-passing the application queue. The Window procedure must then signal the main function that the window is destroyed and that the application should terminate. In the Windows, several applications can be used at the same time and these applications can access to each other with the dynamic exchange. During the preparation of the applications, FoxPro database program is used and DDE is not used to show how data transfers from DOS to Windows. All the programs use Windows resources.