Index_O

O

Online UPS, 402

Ontrack Data Recovery Services, 9, 146, 152

Operating systems

A+ Operating System exam objectives, 375–385

fundamentals, 614–616

hard drives and, 133–138

logical memory, 452–453

“missing” operating systems, 148

MS DOS Command Prompt, 58–61

multitasking, 618

testing tips, 640–642

version checking, 616–618

Optical drives audio cables for, 164–165

BIOS settings, 163

defined and described, 5, 161

diagnosing problems, 168–170

external drive installation, 167

firmware and software for, 166–167

interfaces for, 162–163

jumper settings, 164

maintenance of, 168

noises, 170

opening problems, 169–170

proprietary faceplates for, 165–166

read errors, 168–169, 296–297

removing, 163–164

selection of, 162–163

speed of, 163

troubleshooting, 296–297

write errors, 169, 297

See also CD drives; DVD drives

Optical mouse, 473

Optical storage devices, 539–541

Optomechanical mouse, 473

Oscillator, 422

OSI reference model, 583–585, 850

OSPF (Open Shortest Path First) protocol, 594

Outlook Express, 244–247

Output, defined, 489. See also I/O devices

Ozone filters, laser printers, 512