week1 - Data Organization and Managament Section : 02...

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Data Organization and Managament Section : 02 Lecture Notes Week 1 Prepared By : Mehmet Baysan Ömer Boyacı Mehmet Sinan Esgin Comparison of Storage Devices 1. Primary Memory Capacity: 128 MB - 256 MB Access time: 5´10-7 sec= 50 ms Price: 0.2 $/MB 2. Disk (hard disk) Capacity: 30 GB - 60 GB Access time: 15´10-3 sec= 15 ms Price: 0.003 $/MB = 3 $/GB 3. Winchester (hard disk) Access time: 10-2 sec= 10 ms 4. Floppy Disk Capacity: 1.44 MB Access time: 10-1 sec= 100 ms Price: 0.2 $/MB 5. CD-ROM Capacity: 650 MB Access time: 75 ms Price: 0.002 $/MB 6. DVD (Digital Video Disk) Capacity: 4.7 GB Access time: 112 ms Price: 0.001 $/MB
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1 byte 8 bit 1 char 1 kilobyte (kb) 1024 byte 2 10 byte 1 megabyte (mb) 1024 KB 2 20 byte 1 gigabyte (gb)1024 MB 2 30 byte 1 terabyte (gb) 1024 GB 2 40 byte Example 1: Calculate how many books can be stored in a CD-ROM? Solution: On average there are: 500 words in a page, 1000 pages in a book, 8 characters in a word Total characters in a book: 500 words/page * 1000 pages/book * 8 chars/word = 4.000.000 chars = 4*106 chars= 4 MB A CD-ROM can store nearly 150 (600 MB /4 MB) books. Note: CD-ROM is suitable and important for software distribution for example if you want to distribute “Lotus 1.2.3 for Windows” you need approximately 120 floppy disks because its size is 177 MB. However you can distribute it in only one CD-ROM. Magnetic Tapes: Magnetic tapes used for archival proposes. We can store records on the tape sequentially. Between records we need an empty space, because tapes need some space to start and stop. When a read command comes from computer, tape starts to turn and it has to reach a speed, which is required to read the record. Each record contains some characters and these characters stored as bytes. And each byte contains 8 bits (Actually a byte contains one more bit to check the correctness of the byte).
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Bytes are located horizontally and bits are located vertically. Length of the magnetic tapes are 600/1200/2400 feet/reel and 1 foot = 12 inch = 12’’
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This note was uploaded on 12/01/2011 for the course CS 351 taught by Professor Fazlıcan during the Spring '11 term at Bilkent University.

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week1 - Data Organization and Managament Section : 02...

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