THE OPERATING SYSTEM MACHINE LEVEL - Structured Computer Organization - page 499

the menus, error messages, etc., are kept in country-dependent configuration files.)
NTFS fully supports case-sensitive names (so foo is different from FOO ). The
Win32 API does not fully support case sensitivity for file names and not at all for
directory names, so this advantage is lost to programs using Win32.
As with UNIX , a file is just a linear sequence of bytes, although up to a maxi-
mum of 2 64 1 bytes. File pointers also exist, as in UNIX , but are 64 rather than

32 bits wide, to handle files of the maximum length. The Win32 API function
calls for file and directory manipulation are roughly similar to their UNIX count-
erparts, except that most have more parameters and the security model is different.
Opening a file returns a handle, which is then used for reading and writing the file.
However, unlike in UNIX , handles are not small integers because they are used to
identify all kernel objects, of which there are potentially millions. The principal
Win32 API functions for file management are listed in Fig. 6-39.

−

API function UNIX Meaning

CreateFile open Create a file or open an existing file; return a handle

DeleteFile unlink Delete an existing file entry from a directory

CloseHandle close Close a file

ReadFile read Read data from a file

WriteFile write Write data to a file

SetFilePointer lseek Set the file pointer to a specific place in the file

GetFileAttributes stat Return the file properties

LockFile fcntl Lock a region of the file to provide mutual exclusion

UnlockFile fcntl Unlock a previously locked region of the file

Figure 6-39. The principal Win32 API functions for file I/O. The second col-
umn gives the nearest UNIX equivalent.

Let us now examine these calls briefly. CreateFile can be used to create a new
file and return a handle to it. This API function is also used to open existing files
as there is no open API function. We have not listed the parameters for the Win-
dows 7 API functions because they are so voluminous. As an example, CreateFile
has seven parameters, as follows:
1. A pointer to the name of the file to create or open.
2. Flags telling whether the file can be read, written, or both.
3. Flags telling whether multiple processes can open the file at once.
4. A pointer to the security descriptor, telling who can access the file.
5. Flags telling what to do if the file exists/does not exist.
6. Flags dealing with attributes such as archiving, compression, etc.
7. The handle of a file whose attributes are to be cloned for the new file.