1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<!--Converted with LaTeX2HTML 96.1-h (September 30, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
<HTML>
<HEAD>
<TITLE>Various parts of an operating system</TITLE>
<META NAME="description" CONTENT="Various parts of an operating system">
<META NAME="keywords" CONTENT="sag">
<META NAME="resource-type" CONTENT="document">
<META NAME="distribution" CONTENT="global">
<LINK REL=STYLESHEET HREF="sag.css">
</HEAD>
<BODY LANG="EN" >
<A NAME="tex2html363" HREF="node7.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html361" HREF="node5.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html355" HREF="node5.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html365" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html366" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR>
<B> Next:</B> <A NAME="tex2html364" HREF="node7.html">Important parts of the </A>
<B>Up:</B> <A NAME="tex2html362" HREF="node5.html">Overview of a Linux </A>
<B> Previous:</B> <A NAME="tex2html356" HREF="node5.html">Overview of a Linux </A>
<BR> <P>
<H1><A NAME="SECTION00310000000000000000">Various parts of an operating system</A></H1>
<P>
A UNIX operating system consists of a <b>kernel</b> and some
<b>system programs</b>. There are also some <b>application
programs</b> for doing work. The kernel is the heart of the operating
system<A NAME="tex2html5" HREF="footnode.html#125"><IMG ALIGN=BOTTOM ALT="gif" SRC="./foot_motif.gif"></A>. It keeps track
of files on the disk, starts programs and runs them
concurrently, assigns
memory and other resources to various processes, receives packets
from and sends packets to the network, and so on. The kernel does
very little by itself, but it provides tools with which all
services can be built. It also prevents anyone from accessing
the hardware directly, forcing everyone to use the tools it provides.
This way the kernel provides
some protection for users from each other. The tools provided
by the kernel are used via <b>system calls</b>; see manual page
section 2 for more information on these.
<A NAME="127"> </A>
<A NAME="128"> </A>
<A NAME="129"> </A>
<A NAME="130"> </A>
<A NAME="131"> </A>
<P>
The system programs use the tools provided by the kernel to
implement the various services required from an operating system.
System programs, and all other programs, run `on top of the kernel',
in what is called the <b>user mode</b>.
The difference between system and application programs is one
of intent: applications are intended for getting useful things
done (or for playing, if it happens to be a game), whereas
system programs are needed to get the system working. A word
processor is an application; <tt>telnet</tt><A NAME="305"> </A> is a system program.
The difference is often somewhat blurry, however, and is important
only to compulsive categorizers.
<A NAME="134"> </A>
<P>
An operating system
can also contain compilers and their corresponding libraries (GCC and
the C library in particular under Linux), although not all
programming languages need be part of the operating system.
Documentation, and sometimes even games, can also be part of it.
Traditionally, the operating system has been defined by the
contents of the installation tape or disks; with Linux it is
not as clear since it is spread all over the
FTP sites of the world.
<A NAME="135"> </A>
<A NAME="136"> </A>
<A NAME="137"> </A>
<A NAME="138"> </A>
<A NAME="139"> </A>
<P>
<HR><A NAME="tex2html363" HREF="node7.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html361" HREF="node5.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html355" HREF="node5.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html365" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html366" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR>
<B> Next:</B> <A NAME="tex2html364" HREF="node7.html">Important parts of the </A>
<B>Up:</B> <A NAME="tex2html362" HREF="node5.html">Overview of a Linux </A>
<B> Previous:</B> <A NAME="tex2html356" HREF="node5.html">Overview of a Linux </A>
<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
</ADDRESS>
</BODY>
</HTML>
|
