UNIX Windows NT Name Jing Bai ID 90297

UNIX & Windows NT Name: Jing Bai ID: 90297 Date: 8/28/00

Content 1. Introduction 2. Kernel Architecture 3. File System 4. Memory Management 5. Security 6. Conclusion

Introduction UNIX: • It is a machine independent operating system. Ken Thompson developed it in 1969 • Unix OS was written by programmer to programmer. It use C language to instead of the previously used assembly language • Time-sharing, multi-user, multi-tasking are basic designed in the system(Multiple users can have multiple tasks running at same time) Windows NT • Microsoft released it in 1993. It was a full 32 -bit OS • Its design goals include extensibility, portability, reliability, compatibility, performance and international support.

Unix Kernel model Unix shell User program u s Unix command program library Use level Kernel System call level interface Process management subsystem inter-process communication process scheduling File subsystem Memory management Disk block cache Int process 1 Character I/O Swapper process 0 Block I/O Derive drivers Hardware control-interrupt service Figure 1 =Process Hardware Kernel level Hardware level

Windows NT kernel mode Logon process O/S application Win 16 application Security subsystem O/S system Win 16 VDM Win 32 application MSDOD application POSIX application MSDOS VDM POSIX system Authentication package Win 32 subsystem Security-accountmanage database Executive I/O manager File system cache manager Device drivers User mode Object manager Process Securityreferencemonitor manager network Virtualmemorymanager Local procedure call facility Kernel drive Hardware abstraction Layer Kernel Hardware Figure 2 mode

UNIX File System • UNIX file is a Hierarchical file structure. All the files are organized into a multi-leveled hierarchy called a directory tree • The file system supports two main objects: file and directory • The directory contains a root directory with many subdirectories • File is stored as an array of fixed-size data blocks with perhaps a fragment • The block sizes are set during a file system creation

UNIX File System Interface The root directory / Directory files at interior node A AA B dev Other directories and file AB d 1 a 2 a 3 Normal files at the leaves f 1 d 2 Special files in the device directory/dev

UNIX File System Implementation • IN Unix system, a file is represented by an Inode (Index Node) • An Inode is a record that stores most of the information about a file on the disk, such as its size and location. Each file has an own indoe, all inodes have the same size • The inode contains pointer that points to file block. In Unix, the first 12 pointers of inode point to blocks directly, so small files can be accessed efficiently. • Example for READ file

UNIX mapping of a file descriptor to an Inode Data blocks Read(4. . . ) Tables of open files User space Filestructure table System space In-core inode list Inode list Disk space

UNIX Memory Management • UNIX system uses swapping to handle memory contention among processes. Processes are swapped out until enough memory is available. The process is either in the memory or on the disk. • Decisions regarding which processes to swap in or out are made by the scheduler process. The scheduler wakes up at least once every 4 seconds to check for processes to be swapped in or out • A process is more likely to be swapped out if it is idle, has been in main memory a long time or it is large • A process is more likely to be swapped in if it has been swapped out a long time, or is small

Unix Memory Management • Berkeley introduced paging to UNIX. Paging is added in order to handle a large programs. The basic idea is : some programs don’t need entirety bring into memory to run. Such as text, data. We can bring them to memory by dynamic. When we need them, we can bring in. • Paging can eliminate the external fragmentation of memory. Pagereplacement algorithm can keep enough free frames to support the executing processes.

Window NT File System • The fundament entity in NTFS is a volume. A volume is created by the NT disk administrator utility, and is based on a logical disk partition. The volume may occupy a portion of a disk, may occupy an entire disk, or may span across several disks. In NTFS, all information about the volume are stored in a regular file. • NTFS does not deal with individual sectors of a disk, but instead uses clusters as the unit of disk allocation. A cluster is a number of disk sectors that is a power of 2. The cluster size is configured when an NTFS file system is formatted.

Window NT File System • A file in NTFS is a structured object consisting of attributes. Each attribute of a file is an independent byte stream that can be created, deleted, read, and written. • Every file in NTFS is described by one or more records in an array stored in a special file called the master file table (MFT). The size of a record is determined when the file system is created.

Windows NT Memory Management • The virtual-memory portion of the NT executive is the virtual-memory manager(VM) • The VM manager in NT uses a page-based management scheme with a page size of 4 KB. Pages of data that are assigned to a process but are not in physical memory are stored in the paging file on disk • The VM manager uses 32 bit addresses, so each process has a 4 GB virtual address space. The upper 2 GB is identical for all processes, and is used by NT in kernel mode. The low 2 GB is distinct for every process, and is accessible by both user-and kernel mode threads

Windows NT Memory Management The NT VM manager uses a two-step process to allocate memory. The first step reserves a portion of the process’s address space. The second step commits the allocation by assigning space in the NT paging file. • • The VM manager allows a privileged process to lock selected pages in physical memory thus ensuring that the pages will not be swapped out to the paging file

FILE SYSTEM UNIX • Hierarchical file structure • File and Directory • Block • Inode WINDOWs NT • NTFS • Volume • Clusters • MFT(master file table)

Memory Management UNIX • Swapping • Paging WINDOWs NT • Virtual-memory manager(VM) • Paging File

Conclusion UNIX • Mature and cheaper • Reliability • Configuration do not require a shutdown and reboot • Can setting keyboard and mouse NT • Immature And Expensive • Set up e-mail by separate software • Slow • More crash than UNIX • Less stability than UNIX