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Unit 3: Operating System Structure
Figure 3.1: UNIX Operating System Notes
other programs
sh
nroff nroff
cpp a.out
comp
cc hardware date
as
wc
Id
vi grep
grep
ed
other programs
It’s very common to find pictures like Figure 3.2 below that describe the basic structure of an
operating system.
Figure 3.2: OS Structure Concepts
Applications
Interface
‘Outer’ OS
Kernel
Hardware
You might find that some versions of this have different numbers of rings. What does each part
represent?
1. Hardware: The hardware is, obviously, the physical hardware and not particularly
interesting to us in this module.
2. Kernel: The kernel of an operating system is the bottom-most layer of software present on
a machine and the only one with direct access to the hardware. The code in the kernel is
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