Storage Devices Program Data Secondary Storage Primary Storage

Storage Devices

������� Program ��� Data Secondary ���� Storage �������� Primary ���� Storage

�������� Secondary Storages ���� Files

����� Files u. ASCII File u. Data File u. Document File u. Spreadsheet File u. Source Program File u. Executable Program File u. Graphics File u. Audio File u. Video File

����� File (File Accessing) u. Sequential Accessing u. Direct Accessing (Random Accessing(

�������� u. Batch Processing u. Transaction Processing

Batch Processing u��������� u������ 2 files: umaster file utransaction file u���� :

���� Transaction Processing u��������

Batch ���� Transaction Processing? �������� ����

Secondary Storages u������� Primary Storage

����� Secondary Storages u. Sequential Access u. Magnetic Tape Storage

����� Secondary Storages u. Random Access (Direct Access( u. Magnetic Disk u. CD Rom u. Magneto Opitcal Disk

Magnetic Disk Storage u�������� direct access u�������� bits

����� Magnetic Disk Storage u. Floppy Disk u. Hard magnetic Disk

������ Floppy Disk ��� Harddisk

Tracks track 80 track 00

Sectors sector 01 sector 00

Clusters cluster

File Allocation Table (FAT( File Cluster paper. doc 1 project. xls 2 available 3 database. mdb 4 paper. doc 5 available 6 available 7 available 8 Cluster Address Cluster Track Sector 3 1 4, 5, 6, 7 • FAT ������ file ������ Cluster

File Allocation Table (FAT( File Cluster paper. doc 1 project. xls 2 available 3 database. mdb 4 Paper. doc 5 available 6 available 7 available 8 • ������ save file OS ���� fat ������� cluster ��� 3, 6, 7, 8 ��������� save �� cluster ����� • ������ save �� cluster

File Allocation Table (FAT( File Cluster paper. doc 1 project. xls 2 available 3 database. mdb 4 Paper. doc 5 available 6 available 7 available 8 • ������ cluster ��� 3 ����������� FAT ������ �� ������� save �� � ����������� 6 • ������ save

Harddisk ����� Cylinders Heads

Seek Time Data

Head Switching

Rotational Delay

�������� Harddisk u. Access time u. Seek time u. Head switching u. Rotational delay u. Data transfer rate

�������� Harddisk u. Disk Defragment u. Data Compression u. Using Several Disk

���� Data Compression Uncompressed a b c d 00 01 10 11 Compressed 0 01 10 11 Example: abaaacad Before Compressed: 000100011 (16 bits( After Compressed: 0010011 (11

Magneto-Optical Disk ��������� ����� laser ��� CD Rom

������ Floppy Disk, Harddisk, CD Rom F/L Disk HDD u���� 3 �� 5 �� u���� (��� ) 10 10, 000 u. Bytes / ��� 144, 000 400, 000 CD Rom > 10 �� 75 8, 666