Windows version 3.x supported as many as 64 special functions called printer escapes that applications used to access special device features. An application called these functions by specifying one of 64 predefined values as the second parameter to the Escape function. For example, one of these applications printing on a PostScript printer could draw a PostScript graphic object called a path by calling the Escape function and supplying the BEGIN_PATH and END_PATH values. Most of these escapes are obsolete in the Microsoft® Win32® application programming interface (API) but are provided to simplify the porting of 16-bit Windows-based applications. The Win32 version of GDI supports a complete set of path functions that applications can use instead of the escapes to draw paths on any device. For a list of the Win32 functions that replace some of the escapes, see the Escape function.
Of the 64 original printer escapes, only the QUERYESCSUPPORT and the PASSTHROUGH escapes can be used by Win32-based applications:
Applications written for Windows 3.x can also use QUERYESCSUPPORT and PASSTHROUGH as well as the following 10 escapes. Note that the following escapes are only supported for backwards compatibility with Windows 3.x-based applications. The Escape function may fail if a Win32-based application uses any of these.
In addition to supporting Escape, the Win32 API provides an extended escape function called ExtEscape. This function allows applications to access capabilities of a particular device not directly available through GDI.