Operating System Structure

Operating System Design Goals
Types of System Calls
Additional Operating System Functions
System Calls
Operating System Services
Operating System Design
Benefits of a Microkernel
Layered Approach
Communication Models
User goals – operating system should be convenient to use, easy to learn, reliable, safe, and fast.
System goals – operating system should be easy to design, implement, and maintain, as well as flexible.
- Process control
- create/terminate process
- File management
- create/delete file
- Device management
- request device
- Information maintenance
- set time and date
- Communications
- create/delete communication connection
- Protection
- set permission
- to ensure efficiency system operations
- Resource allocation
- Accounting
- Protection and security
provide the interface between a
running program and the operating
- 1. pass the parameter in registers
- 2. parameters stored in a block, or
table, in memory, and address of block
passed as a parameter in a register
- 3. parameters placed, or pushed, onto
the stack by the program and popped
off the stack by the operating system
- User interface
- Program execution
- I/O operations
- File-system manipulation
- Communications
- Error detection
Design and Implementation of OS not “solvable”, but
some approaches have proven successful.
 Start by defining goals and specifications
The design of the system will be affected by the choice
of hardware and the type of system: batch, time
shared, single user, multiuser, distributed, real time or
general purpose.
- Extensibility
o Allows the addition of new services
- Flexibility
o New features added
o Existing features can be subtracted
- Reliability
o Modular design
o Small microkernel can be rigorously
- Portability
o Changes needed to port the system
to a new
processor is changed in the microkernel
- not in
- small operating system core
- contain only essential core operating
system function
Many services traditionally included in
the operating system are now external subsystems
- Device drivers
- File systems
- Virtual memory manager
- Windowing system
- Security servicesSecurity services
- In layered approach, the Os is divided
into a number of layers, each built on
top of lower layers.
- Advantage
- Simplicity of construction and
- Disadvantage
- The careful definition and
interaction of the layers
- Less efficient
- Layered Operating System
- Message passing
- In message passing
model, communication takes place by
means of messages exchanged
between the processes.
- Shared memory
- In shared memory model, a region of
memory that is shared by processor
can exchange information by reading
and writing data to the shared region.