Shared display, memory, keyboard, mouse, and system timerA Windows application can take advantage of a number of features provided by the API. These features include the following:
Shared display, memory, keyboard, mouse, and system timer
Data interchange with other applications
Device-independent graphics
Multitasking
Dynamic linking
Windows allows applications, running simultaneously on the system, to share hardware resources; application developers do not need to write specific code to accomplish this complex task.
The clipboard, another Windows feature, acts as a place for data interchange between applications. The information sent between applications can be in the form of text, bitmaps, or graphic operations. Windows provides a number of functions and messages that regulate the transmission of information with the clipboard. These functions and the corresponding messages are part of the window manager interface, one of several libraries in the API.
Windows contains functions that an application can use for device-independent graphic operations. These functions create output that is compatible with raster displays and printers of varying resolution, as well as with a number of vector devices (plotters). These functions are part of the graphics device interface (GDI), the second of the API libraries.
Windows provides multitasking, which means that several applications can run simultaneously. The functions that affect multitasking and memory management in general are part of the system services interface, the third API library.
Because of the memory limitations imposed by DOS, it is important to keep applications as compact as possible. Windows accomplishes this compaction through dynamic linking and the use of discardable code, which allows an application to load and execute a subset of the library of functions at run time. Only a single copy of a library is necessary, no matter how many applications access it.