IBM’s OS/2
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Transcript of IBM’s OS/2
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IBM’s OS/2
by
Chris Axford
Chris Evans
Elizabeth McGinnis
Erik Swensson
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HISTORY
• IBM and Microsoft partner to make DOS replacement
• 1987 OS/2 version 1.0
• 1989 OS/2 version 1.2
• 1994 OS/2 Warp
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Hardware Platforms and Devices
• Earliest version used Intel’s 80286 and 80386
• OS/2 Warp has expanded hardware compatibility
• Communication Devices
• 2 MB RAM
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User Interface
• OS/2 version 1.0 used command line interface
• OS/2 version 1.1 provided Presentation Manager
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Process Control Block
• Standard Format
• Traditional Aspects– Pointer– Process ID– Process State– List of Open Files– Program Counters and Registers
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Multitasking
• Multiple threads per process (user and kernel)
• Standard information– Thread ID– Stack– Processor registers– Dispatch state– Priority
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Process Communication and Synchronization
• Shared Memory
• Pipes
• Queues
• Semaphores– System Semaphores– RAM Semaphores
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Scheduling
• Multilevel Queue Scheduling Algorithm
• 4 Priority groups– Time Critical, Server, Regular, Idle– 32 Queues for each group: total– Each Queue uses Round Robin– Priority Boasts Possible
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Memory Management
• Memory Protection
• Virtual Memory and LRU Algorithm
• Memory Segment Sharing
• Memory Size Changes
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FAT File System• Singly-linked cluster implementation of disk blocks
• Fixed size root directory
• Advantages
• Disadvantages
Layout of the 32 bytes in a directory entry in a FAT system. Source: http://www.edm2.com/0411/hpfs1.html
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HPFS – High Performance File System
An HPFS file entry
Length of file
File attributes
Pointer to HPFS structure
Date/ Time stamp
Usage count
Length of file (up to 254 characters)
Pointer to next level in structure
•Why the need for HPFS?
•Balanced Tree Structure to store files
•Advantages to FAT
•Disadvatages to FAT
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In Conclusion…