管理信息系統(tǒng)計(jì)算機(jī)硬件軟件-wenkub
2022-08-31 16:50:56 本頁(yè)面
【正文】 PS: BLOCKING FACTOR (., 10 records per block) ? GROUPS SEPARATED BY INTERBLOCK GAP ? RECORDS READ BLOCK AT A TIME * HEADER IBG BLOCK 1 BLOCK 2 BLOCK 3 MAGNETIC TAPE ? ENCLOSED FERROUS OXIDE TAPE ? USED PERIODICALLY TO BACK UP RECORDS ? INEXPENSIVE ? STORED IN SAFE LOCATION ? CAN BE REUSED MAGNETIC CARTRIDGE ? CDROM: 500660 MEGABYTES –LAND: FLAT PARTS OF DISK SURFACE REFLECTS LIGHT –PITS: SMALL SCRATCH ON SURFACE SCATTERS LIGHT ? WORM: WRITE ONCE / READ MANY ? ERASABLE OPTICAL STORAGE (EOS) DISKS * OPTICAL STORAGE MULTIMEDIA WORKSTATION CDROM HEADPHONES STEREO SPEAKERS LEFT, RIGHT, WOOFER SUPER VGA MONITOR VIDEO BOARD + EXTRA MEMORY STEREO SOUND BOARD (32 BIT: WAV, MIDI, CD) AT LEAST 16 MG RAM (32 MG MUCH BETTER) JOYSTICK HARD DRIVE: 1 GIG OR MORE, JAZ DRIVE 通訊網(wǎng)絡(luò)的組成 “ Any one in the world could be your customer。 any one in the world could be your petitor.” 網(wǎng)絡(luò)模型 Network Model: A munication work is any arrangement where a sender transmits a message to a receiver over a channel consisting of some type of medium 第 6章 通信與網(wǎng)絡(luò) 圖 6. 1 以單計(jì)算機(jī)為中心的遠(yuǎn)程聯(lián)機(jī)系統(tǒng) 圖 6. 2 存儲(chǔ)轉(zhuǎn)發(fā)的計(jì)算機(jī)網(wǎng)絡(luò) 組織的數(shù)據(jù)庫(kù)通過(guò)M o d e m 遠(yuǎn)程訪問(wèn)中央服務(wù)器( 總部）局域網(wǎng)A局域網(wǎng)B局域網(wǎng)C局域網(wǎng)E局域網(wǎng)D圖 6. 4 某人壽保險(xiǎn)公司的局域網(wǎng)和廣域網(wǎng) 圖 點(diǎn)到點(diǎn)式網(wǎng)絡(luò)的拓?fù)浣Y(jié)構(gòu) (a)星 型結(jié)構(gòu) (b)環(huán) 型結(jié)構(gòu) (c)樹(shù) 型結(jié)構(gòu)圖 6. 6 廣播式網(wǎng)絡(luò)拓?fù)浣Y(jié)構(gòu) 衛(wèi)星(a)總線型 (b)衛(wèi)星和無(wú)線電式圖 同軸電纜結(jié)構(gòu)圖 圖 6. 8 光纖傳輸 1 2 3 4 5 End user Tele Tele Tele puter processors Channels processors amp。 efficiency. 3. Telemunication channels amp。 Research Network ( CERNET ) China MPT Network
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