Matakuliah
Tahun
Versi/Revisi
: T0316/sistem Operasi
: 2005
:5
Pertemuan 3
Konsep Sistem Operasi
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• menjelaskan istilah dan konsep sistem operasi
(C2)
2
Outline Materi
Konsep
– Processes
– Deadlock
– Memory
management
– I/O
– File
– Shell
– System call
Struktur
–Monolithic
–Layered
–Virtual machine
–Exokernels
–Client-Server
3
 OPERATING SYSTEM CONCEPT
Process
- Program in execution
- Consist of:
o Executable program, data, stack
o Program counter, stack pointer, registers
- Process table  array or linked list of structure of the process in
execution
- Process has:
o Address space (core image)
o Attribute/information in the process table
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- A process tree:
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Deadlock
- Condition in which interacting process cannot be continued and
there is no process that can get out of that condition.
(a) A potential deadlock. (b) an actual deadlock.
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Memory Management
- Multiple program dalam memory  needs:
o Protection
o Address space management
Input/Output
- Independent I/O software
- Device dependent, eg. device drivers
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 Files
- Directory
- Pathname
- Protection mode
 rwx bits
- File descriptor
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- Mounted file system
Before mounting
After mounting
- Special file
o Block
o Character
- Pipe
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 Security
- Protection, eg. rwx bits
- Intruders, from human or non-human (eg. virus)
 Shell
- Unix command interpreter
- Prompt
Example:
date
date > file
sort < file1 > file2
cat file1 file2 file3 | sort > /dev/lp
cat file1 file2 file3 | sort > /dev/lp &
- Background job
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SYSTEM CALLS
Interface between user program and operating system
Steps in Making a
System Call
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- Example of system calls:
o Process Management
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o File Management
o Directory and file
system
management
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o Miscellaneous
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 OPERATING SYSTEM STRUCTURE
Monolithic system
- The big mess
- No structure
Simple structuring model
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Layered System
- Hierarchical layer, each layer is built on top of the layer
below it.
- Eg: THE system
Generalisation of layering concept at MULTICS  concentric ring
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Virtual Machine
- Virtual machine monitor  not an extended machine, but an
exact copy of the bare hardware
- CMS (Conversational Monitor System)
- JVM (Java Virtual Machine)
Structure of VM/370 with CMS
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Exokernels
- Designed for a system that gives each user clone of the actual
computer, but with a subset of resources
- Program run on the bottom layer to allocate resources to
virtual machine
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Client-server model
- Mikrokernel
- Client process
- Server process
- Mechanism vs policy
The client-server model
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The client-server model in a distributed system
Advantages of distributed system model:
- Smaller parts are easier to maintain
- No direct access toward hardware
- Adaptability
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