The loading of device drivers in both Windows 95 and OS/2 Warp has greatly improved since DOS had become the operating system. They have given users more flexibility to decide what driver to load for which program when running Windows and DOS programs. Windows 95 take a step further as to load the CONFIG.SYS only when a program is launched. Hence, each program can have different CONFIG.SYS file. OS/2 Warp, on the other hand, has a more complicated CONFIG.SYS file though users can also run different AUTOEXEC.BAT for different program. This features reduce potential conflict between drivers and programs.

OS/2 Warp employs the flat memory addressing method when running OS/2 native programs. Hence, there is no magic 640 Kb limit. OS/2 Warp also emulates DOS machines by what is called the Virtual DOS Machine (VDM), which each DOS and Windows program running under OS/2 will have their own segment of memory. This eliminates the Single System VM problem where a not well behaved program can potentially bring down the whole system by trying to access memory that is not allocated to the program. This is not the case in Windows 95. It still employs what was used in Windows 3.x, the Single System VM. Linux, like other UNIX systems and OS/2 Warp and hance, the system integrity is maintained and is more robust.

Windows 95 does not perform preemptive multitasking like Linux and OS/2 Warp when running the 16-bit Windows 3.x programs. These 16-bit programs will decide when to give up control on the CPU usage and let other programs have a slice of the CPU time. This method of multitasking is called cooperative multitasking or task-switching. Linux and OS/2 Warp will run any program together written for it with ease though OS/2 Warp DOS and Windows programs running in OS/2 Warp take up more CPU time than native programs because these programs are not designed to give up CPU time voluntarily and OS/2 Warp has to control these programs. This giving up control involuntarily by the running program is called preemptive multitasking.

In Windows 95, certain programs will only run in so called DOS MODE. On activation of such programs, the operating system has to shut down all other running programs and give full control to this DOS MODE only program. This method of handling programs is not what a multitasking system should do. We hope that future release of Windows will make improvements in this situation.

February 20, 1996

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