Transcript Advanced OS 01

Operating Systems
Advanced OS - A
OS Advanced
Basic OS Functions
OS Advanced
Bytes & Words
Bit = 1 or 0
Byte = 8 Bits or a Character
OS Advanced
Words
Bytes are too small to represent
meaningful numbers, thus most
computers manipulate a group of
bytes called a WORD
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Words
16-bit (2 Byte)
32-bit (4 Byte)
64-bit (8 Byte)
OS Advanced
We have a hierarchy of memory:
Bits are grouped to form Bytes, and
bytes are grouped to form Words
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Most computers are designed
around the Word size.
32-bit Word means that the CPU
manipulates 32-bit numbers,
memory stores 32-bit words.
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The biggest 32-bit number is
approximately 4 Billion in decimal
terms. So a 32-bit processor can
access as many as 4 billion
different memory locations.
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The bigger the Word size the more
memory a computer can address.
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A bigger Word size influences a
systems cost.
But a bigger Word size generally
means a faster, more precise
computer, with greater memory
capacity, larger instruction set, but
a higher price tag.
OS Advanced
The Operating System (OS)
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Computers are not Intelligent!
They must be given instructions
before they can perform any
operation.
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The OS system module that
accepts, interprets, and carries out
commands (defines the user
interface) is called the
Command Processor
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Command
Processor
SHELL
OPERATING SYSTEM
HARDWARE
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Programmers & Users
communicate with the command
processor (Shell) by issuing
commands, the shell interprets the
commands and passes them to the
operating system (OS)
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The Command Processor contains
routines which perform a single task
The set of commands forms a
command language.
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Command Processor
Run Program
Load Program
Create File
Open File
Close File
Format Disk
List Directory
Check Disk
Others
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The OS is tasked with
communicating with the computers
hardware
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OS uses the
Input/Output Control System (IOCS)
Physical Disk Management
The IOCS communicates directly
with hardware via unique primitive
commands
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Primitive Commands
Seek
Read
Write
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File System
Logical Disk Management
Helps us keep track of data files
and program files
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Data Files
Created and Accessed by
Application programs
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Program Files
When Installed the name and
physical location is recorded in the
Directory (Folder)
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File System
Responsible for allocating space on
a disk for a file
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Differences between
IOCS & File System
IOCS
FILE SYSTEM
Direct
Communication
Logical
Communication
Primitive Level
Logical Level
Used by File System
Uses IOCS
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The computer clock synchronizes
the CPU and Memory
All other devices work
asynchronously.
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Other devices communicate with
the CPU via an Interrupt
(Interrupts can be issued by
Software also)
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Interrupt
An electronic signal, sensed by
hardware, which causes an
interruption in the OS which then
handles the task requested until it
is complete, depending on its
priority in the IRQ stack
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Interrupt
There are typically 16 IRQ’s
available for use on an IBMCompatible computers
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THE BOOT
OS must be in memory before any
other functions can begin
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OS’s are typically stored on a disk
(HD, CD) and must be loaded into
memory via a software program
called the Boot program
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Generally stored on the first few
sectors of a disk
Hardware is designed to read the
Boot automatically when power is
turned on
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Loading the OS from scratch is
called the Cold Boot
Loading the OS and bypassing
preliminary processes is
called the Warm Boot
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The OS is vital to the operation of
computers, and is required to have
a functioning and useful computer
system.
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Questions?