all of sani

Personal computers PCs appeared in the 1970s. During their decade, the CPUs in PCS lacked the features needed to protect an operating system from user programs. PC operating systems therefore were neither multiuser nor multitasking. However, the goals of these operating systems have changed with time; instead of maximizing CPU and peripheral utilization, the systems opt for maximizing user convenence and responsiveness. These system include PCs running microsoft windows, and IBM has upgraded MS-Dos to the OS/2 multitasking system. The Apple Macintosh operating system has been ported to more advanced hardware, and now includes new features, such as virtul memory and multitasking. With the release of MacOS X, the core of the operating system is now based on match and freeBSD Unix for scalabillity, perfomance, and features, but it retains the same rich GUI,Linux, a UNIX-like operating system avilable for PCs, has also become popular recently .
Operating systems for these computers have benifited in servel ways from the devlopment of operatingsystems for mainframes. Microcomputers were immidiately able to adopt some of the technology devloped for larger operating systems. On the other hand, the hardware costs for microcomputers utilization is no longer is no longer a prime concern. Thus, some of the design decisions made in operating systems for mainframes may not be appropriate for smaller systems.
Other design decisions still apply. For example, file protection was at,first, not necessary on a personal machine. However, these computers are now often tied into other computers over loca-area networks or other Internet-connections. When other computers and other users can access the files on a PC, file protection again becomes a necessary features of the operating systems. The lack of such protection has made it easy for mulicious programms to destroy data on systems such as MS-DOS and the Macintosh operating system. These programs may be self-replicating, and may speread via worm or virus mechanisms and disrupt entire companies or even worldwide networks. Advanced time-sharing features such as protected memory and file permissions are not enough, On their own, to safeguard a system from attack.Recent security breaches have shown that time and again.