Labels:reckoner | sky | trade name OCR: Application programs DOS Device drivers BIOS Hardwara (memory disks keybcard display adap ters speaker and so on FIGURE 3.1 The traditional view of the PC's resources in which an plication programs rest on layers of svstem software and hardware. In this scheme, application programs are sup posed to communicate only with the highest possible (preferably DOS although they can necessary make end runs around the layers directly to any needed level While this arra ngement has advantages as regards portabilins and compatibility with future computers and operating svstems is less than ideal for performarce. keyboard lavers system layer portability systems
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