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Chap. 2 : Operating-System Structures (one set of OS sevices (User…
Chap. 2 : Operating-System Structures
OS provide an environment for execution of programs and services to programs and users.
one set of OS sevices
User Interface
Program Execution
I/O Operation
File-System Manipulation
Communication
Error Detection
Another set of OS function exist for ensuring the efficient operation via
resource sharing
Resource Allocation
Logging
Protection and Security
CLI
Allow direct command entry
sometime implemented in kernel, sometime by system program
sometime multiple flavors implemented -- shells
fetches a command from user and executes it
sometime command build-in, sometime just name of programs
GUI
User-friendly desktop metaphor interface
eg: mouse, keyboardd, monitor, icons represent files, programs, actions
inverted at
Xerox PARC
TouchScreen Interfaces
require new interfaces,, mouse not desired, actions & selection based on gestures, virtual keyboard, voice commands
System Calls
programming interface to the services provided by the OS
Type
Process Control
File Management
Device Management
Information Maintanance
Communication
Protection
mostly access by programs via high-level
APPLICATION PROGRAMMING INTERFACE (API)
implementation
a number associated with each system call
System call interface invokes the intended system call in OS kernel and returns status of the System call & any return values
the caller need know nothing about how the system call is implemented but needs to obey API & understand what OS will do as a result call
Parameter Passing
3 general methods
Simplest : pass the parameters in register
Parameters stored in block, or table, in memory & address block passed as a parameter in a register
paarameters placed, or pushed, onto the stack by the program & popped off the stack by the operating system
block & stack methods do ot limit the number or length of parameters being passed
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