Page 328 - DCAP103_Principle of operating system

Unit 10: Introduction of Windows and its Programming

Processes, threads, synchronization, memory management, file I/O, and security system calls Notes
are nothing new. Other operating systems have them too, although generally not hundreds of
them, as Win32 does. But what really distinguishes Win32 are the thousands upon thousands
of calls for the graphical interface. There are calls for creating, destroying, managing and using
windows, menus, tool bars, status bars, scroll bars, dialog boxes, icons, and many more items that
appear on the screen. There are calls for drawing geometric figures, filling them in, managing the
colour palettes they use, dealing with fonts, and placing icons on the screen. Finally, there are
calls for dealing with the keyboard, mouse and other input devices as well as audio, printing,
and other output devices. In short, the Win32 API (especially the GUI part) is immense and
we could not even begin to describe it in any detail in this unit, so we will not try. Interested
readers should consult one of the many sites on Win32.
Although the Win32 API is available on Windows 98 (as well as on the consumer electronics
operating system, Windows CE), not every version of Windows implements every call and
sometimes there are minor differences as well. For example, Windows 98 does not have any
security, so those API calls that relate to security just return error codes on Windows 98. Also,
Windows 2000 file names use the Unicode character set, which is not available on Windows
98 and Windows 98 file names are not case sensitive, whereas Windows 2000 file names are
case sensitive (although some kinds of searches on file names are not case sensitive). There are
also differences in parameters to some API function calls. On Windows 2000, for example, all
the screen coordinates given in the graphics functions are true 32-bit numbers; on Windows
95, only the low-order 16 bits are used because much of the graphics subsystem is still 16-bit
code. The existence of the Win32 API on several different operating systems makes it easier to
port programs between them, but since these minor variations exist, some care must be taken
to achieve portability.

How to differentiate between Win32 and Win64?

10.2.2 Registry
Windows needs to keep track of a great deal of information about hardware, software, and users.
In Windows 3.x, this information was stored in hundreds of .int (initialization) files spread all
over the disk. Starting with Windows 95, nearly all the information needed for booting and
configuring the system and tailoring it to the current user was gathered in a big central database
called the registry. In this section we will give an overview of the Windows 2000 registry.
To start with, it is worth noting that although many parts of Windows 2000 are complicated and
messy, the registry is one of the worst, and the cryptic nomenclature does not make it much
better. Fortunately, entire sites have been written describing it. That said, the idea behind the
registry is very simple. It consists of a collection of directories, each of which contains either
subdirectories or entries. In this respect it is a kind of file system for very small files. It has
directories and entries (the files).
The confusion starts with the fact that Microsoft calls a directory a key, which is definitely not.
Furthermore, all the top-level directories start with the string HKEY, which means handle to
key. Subdirectories tend to have somewhat better chosen names, although not always.

At the bottom of the hierarchy are the entries, called values, which contain the information.
Each value has three parts: a name, a type, and the data. The name is just a Unicode string, often
default if the directory contains only one value. The type is one of 11 standard types. The most
common ones are Unicode string, a list of Unicode strings, a 32-bit integer an arbitrary length

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