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Issue 3 (Jan 31, 2000)
___________________________________________________________________________
The gh0st.net project: http://www.gh0st.net/index.html
FireSt0rm's homepage: http://www.firest0rm.org/index.html
URL of the day: http://napalm.firest0rm.org/index.html
All content copyright ©2000 by the individual authors, All Rights Reserved
___________________________________________________________________________
- Editor's Comments
- URLs
- Building a HERF Gun (2 parts)
- AI Security
- C++ Tutorial
- Future Issues
- Credits
***********************************************************************
*** Editor's Comments : Kynik
***********************************************************************
The webserver for gh0st.net has been bouncing around lately, and will
stabilize soon at its new hosted home. You will be able to see Napalm at
its own subdomain http://napalm.gh0st.net/ and eventually at
http://napalm.firest0rm.org/ when I get around to setting up the box,
domain name, and configuring some crap. The gh0st.net and FireSt0rm lads
are all helping me put together a damn good whitepaper that will probably
appear as a special edition of Napalm as soon as everything gets finalized.
Keep an eye out!
During the review process, our good friend Snock decided he had enough
comments on the HERF article to make a followup/clarification of his own.
Enjoy!
***********************************************************************
*** Random good URLs : Kynik, Blakboot, Hubbo
***********************************************************************
FAQ on Neural Nets
ftp://ftp.sas.com/pub/neural/FAQ.html
Good Code Security Guidelines from OpenBSD
http://www.openbsd.org/porting.html
GNU Coding Standards
http://www.gnu.ai.mit.edu/prep/standards.html
Review unsigned bands (Use cynic@execpc.com as your referrer)
http://www.garageband.com/
A primer on prime numbers
http://mindsong.net/science/primes.txt
CoreWars? Not the programming game - a (dead?) hacker wargame
http://www.corewars.net/
Secure Remote Streaming - a secure replacement for syslog
http://www.w00w00.org/files/SRS/
***********************************************************************
*** Building a HERF Gun (part 1) : c_routine
***********************************************************************
Introduction
------------
I certainly hope that you enjoy this small slice of high energy physics
and if you find any error, don't hesitate to email me and correct me.
c_routine()
routine@gh0st.net
Dr. I. Fuxom
fuxom@go-away-I-hate-you.mil
Disclaimer
----------
The author(s) of this article are not responsible for any damage caused by
the knowledge gained within the confines of this article, whether they be
damage of persons, property, or any other entities, living, dead, or
otherwise. The information contained herein is designed to be used for
informational or entertainment uses only. The reader assumes all
responsibility for the usage of the information contained within.
[ Aww c'mon, routine... you know you want people to blow stuff up {kynik} ]
Part One
--------
This article assumes that you have some working knowledge of RF theory
and of the concept of HERF. It also assumes basic electronics knowledge.
[ And for those of you that don't: RF=Radio Frequency & HERF=High Energy
Radio Frequency {kynik} ]
HERF pulse cannon inventory
---------------------------
There are several parts to a HERF pulse cannon:
1) Energy
2) Magnetron
3) Focusing device
4) Micro$hit building (also known as: Target)
First: Energy
-------------
The energy requirements of a HERF pulse cannon are quite great. You'll
need approximately 10,000 Farads to get a decent pulse. The best way of
storing and releasing this much energy is in the form of a capacitor. You
should realize that capicitors are not generally built with ratings of
10,000F. If anyone knows of an industrial electronics company that does
manufacture high-rating capacitors, please let me know. Of course, they do
make caps with ratings of pF and uF.
[ That's putting it mildly. A 10kF cap would be, shall we say, a little
unwieldly. I've been considering scavenging some 1000uF caps from old
power supplies for a very-low-power HERF device; 1000uF = .1F. {ajax} ]
Please observe the following:
-------
Sum of capacitance when connected in parallel.
C = C1 + C2 + C3....
-------
Therefore, the best way is to parallel enough capacitors together in
order to create a rating of about 10,000F.
Being familiar with capacitors, you should know that when you discharge
a capacitor, the whole amount discharges at once. This is your pulse.
Unfortunately, this is only DC power and what you want is RF. Enter the
magnetron.
Second: Magnetron
-----------------
The magnetron is the actual RF generator. It takes the high power DC
pulse and turns it into a big RF pulse. It's a high power oscillator,
basically.
In order to get power out of the tube (and it is a tube) just apply the
proper heater voltage for the tube (carefully measure the voltage on the
existing transformer, without the HV connected of course) then apply
about 5kV to the anode (cathode/heater negative, anode positive) from a
big cap. Most standard oven tubes can take about 1kW/Sec without going
into meltdown. The result is a huge pulse of RF coming out of the
waveguide coupler.
Note: Do NOT do this with the tube just laying on a table! That much
RF, if you expose yourself to it can cause sterility, cataracts, or
literally cook you inside. It only takes a fraction of a second at high
power to do that. Really, take a LOT of precautions when you experiment
with that much power.
[ Yeah, think how nervous you'd be if you sat in a microwave for a moment
while it was on. Scary stuff. Though it did work in Gremlins. {kynik} ]
[ The Gremlins were so cute... Actually, one guy got a Darwin Award for
something similar, like falling asleep in front of a microwave dish.
Like routine says, we are not responsible for anything you do to
yourself. {ajax} ]
[ Brings a whole new meaning to "You snooze, you lose." {kynik} ]
Third: Focusing Device
----------------------
A parabolic dish would be the easiest way. Procure a book with the
design info for a parabolic dish, just go by the frequency of the tube
(usually around 7 Gig or so) to get the focus point and minimum diameter.
Fourth: Target
--------------
As of yet, this is an untested method, but as soon as I fully assemble
a HERF pulse cannon, I'll be taking a drive up to Redmond to see how well
it really works. On the Micro$hit building!
More information (along with this article archived online) on this subject
can be found at my HERF website: http://www.gh0st.net/~routine/
[ Or rather, might be found; as of my review this site is empty. {ajax} ]
[ Yeah, probably have to wait for the full webserver move. {kynik} ]
***********************************************************************
*** Building a HERF Gun (part 2) : Snock
***********************************************************************
Disclaimer
----------
I'm not responsible for your use or misuse of this information, yadda
yadda yadda.
Introduction
------------
HERF, or high energy radio frequency devices are classified as HPMs, or
high powered microwave. It works by pushing very high current pulses which
last only a small fraction of a second into a magnetron tube which then
releases a burst of microwave energy upon excitation. The output from this
system is quite "ragged". The microwave energy induces current into nearby
objects in its path causing them to possibly malfunction. Magnetrons can
also be used to remotely power devices as well. The circuit below is just
a rough idea of one might to do create a small scale high power pulsed
microwave "gun". In normal operation the magnetron's output is much more
clean than the circuit below provides. The "clean" continuous output of
the magnetron creates much more surface heating.
[ I'd be interested in hearing more about how this technology can be used
to remotely power something. There's been some minor discussion on the
topic on the L0pht BBS, but nothing in-depth. Interested, Snock? Perhaps
a Part 3 to this? {kynik} ]
Main parts involved
-------------------
Magnetron: This is the device that produces the microwave RF energy. In
microwave ovens this is the (usually) square finned object
that it attached to the chassis on the upper right side near
the rear of the unit. It is a vacuum tube that has heater
filament connections and the high voltage connections as well
as an output waveguide/antenna. Microwave ovens operate at
roughly 2.5GHz. The filaments generally require about 3-4
volts for operation.
Capacitor: A capacitor is an electrical storage device. The most simple
implementation of a capacitor is simply two conductors
separated by a dielectric. The dielectric is the material
between the conductors and has an impact on the storage
capacity. Surface area also increases capacitance and this is
why flat plates are used in their design.
Sparkgap: This is nothing more than two or more electrodes seperated at
a certain distance. Sparkgaps serve as high voltage switches.
When a certain voltage threshold is reached the material
(usually air) breaks down and a conductive channel is formed,
ie a spark. Several methods may be employed to help the gap
operate, or "quench" more effectively. Parallel electrodes,
forced air flow, and gaps which physically rotate are some of
the methods that may be used to decrease spark dwell times and
excessive arcing at the gap.
Schematic
---------
T1* ~4000Vrms .01uF (experiment)
||(---|<|---+------||----------+
~AC--------)||( | | /
)||( o Magne | /|/|/|/|/|/|/|-->>
120VAC )||( o tron \ Microwave pulses
)||( | |
~AC--------)||(---------+------------------+
||(--------> ~3VAC to filament
||(--------> ~3VAC to filament
In microwave ovens the high voltage capacitor serves its function in a
voltage doubler circuit. The magnetron itself actually runs off of roughly
5000V compared to the ~2000Vrms output of the large transformer.
I don't recommend the transformer that is in the microwave oven to be
used as it is quite deadly... especially to the careless. Rather than
that, try to find an old neon sign transformer (T1) with a rating of around
4000VAC at 30-60mA. Neon shops will often give them away if you ask. The
rectifier diode in the above circuit is the one that is found in the oven.
These diodes are typically rated to withstand about 12-15kV peak inverse
voltage. The capacitor is typically a homebuilt unit. You can make these
quite easily from beer bottles, foil, salt water, and long bolts. Using
glass bottles makes it quite easy to experiment with the capacitance of the
circuit since you can add and remove as you please. If you don't use the
bottles, then use capacitors of the appropriate rating (two times the RMS
output of the transformer *at least*) and make sure it will withstand pulse
discharging. Capacitors may burn up or explode if the ratings are ignored.
The sparkgap can be constructed with two carriage bolts with the bolt heads
as the electrode faces (where the sparks make contact). You can take
advantage of the threads on the bolts as a way to fine tune the gap
spacing. Try to get the gap as wide as possible while still allowing spark.
The filament windings on the original microwave oven transformer are
typically 3VAC at around 10-15A. You can also subsitute this with a
transformer of similar voltage/current capacity. RF chokes before the
sparkgap on each leg of the transformer may also be a good idea to help
keep noise out of the building electrical system.
Operation
---------
Operation is fairly straight forward. A parabolic reflector will provide
a greater distance and effectiveness of the device. You should keep good
distance and always keep away from the antenna of the magnetron. Distance
is a good way to minimalize exposure to radiation. Never touch any of the
components on the circuit during operation. While the current from the
transformer to the sparkgap may only be 30-60mA, the current past that is
quite deadly. After shutting it off you should discharge the capacitors.
If the are film type capacitors they should be stored shorted to prevent
bad shocks from static buildup on the plates. The magnetrons generate
quite a bit of heat as they are only about 50% efficient, so they should
also be cooled. This circuit also generates a *hell* of a lot of noise
(both AF and RF) and will more than likely cause your neighbors to become
pissed.
Related links/more info:
http://www.zdnet.com/zdnn/stories/news/0,4586,2331772,00.html?chkpt=hpqs014
http://www.house.gov/jec/hearings/radio/schriner.htm
***********************************************************************
*** AI Security - Detection and Prevention : Blakboot
***********************************************************************
Introduction
Credit goes to the following people (A-Z): Ajax, Echo8, Kp2, Kynik, and
everyone who helped from #osuny. With Kp2's consent, I'd like to develop
some of this for Gh0stOS, though other things mentioned herein are
hypothetical.
In this paper I will discuss a few security concepts which are related
to artifical intelligence. My next paper will be a thorough explanation
of examining nonlinear data with neural nets; in it I'll include new and
original source code. All of this was originally written for the PSS
Storm Chaser 2000 contest, hence its whitepaper look and "wordyness".
Please excuse that shit.
Vulnerability Scanning and Automated Patching
"A system can be made secure, but the problem lies in change - when new
software is taken into the system."
Security breaches are often the result of the adoption of new software
with exploitable vulnerabilities. The author proposes two methods: 1.
Vulnerability scanning and 2. Automated patching. Vulnerability scanning
is the more theoretical area of defence; the author considers automated
patching the most feasible option.
Automated Patching
The security daemon will take it upon itself to contact the providers of
the software via a secure protocol, and/or connect to the provider's
patch-protocol to automatically receive fixes on a timely basis. This
protocol is a security issue itself, though with proper encryption and
certification, patches can be transfered confidently. This patch
installation technique will solve many problems because often
administrators do not install patches soon after they are developed. This
proactive patching of vulnerablities can a powerful tool, preventing many
intrusions by staying one step ahead of those who await the development
of exploits. Most intrusions today are the result of attackers taking
advantage of exploits released to the public and automated patching is
the solution for systems that are to remain secure against ever-evolving
intrusion techniques. It will put security patches in place or at the
feet of decision-making administrators.
Due to the possibilty of program patches changing the functionality of
these programs, the system could be crippled. Thus, programs sent from
the providers' protocol must be flagged ready to be patched with no
changes in the functionality, or flagged as a change in functionality
standards. If it has considerable changes, the security daemon will still
accept the patch, but will not install it. The next step would be to
notify personnel, and leave it to them to change the program's
configuration and install the patch.
Vulnerability Scanning
The system enters a stage of introspection, examining the source code
of programs for vulnerabilities. If the program analysis is expected to
take away considerable cpu time, it should be conducted a time of least
usage of system resources.
[ Or it could be done distributed.net style in the computer's idle time
all the time. {kynik} ]
For example, if an exploitable buffer overflow were to be discovered,
the security daemon would remove any administrative privileges from the
program (remove suid root) or simply remove execution privileges, notify
security personnel and attempt to repair the problem by modifying the
source code. If the patch is unsuccessful, the source code is restored
and execution is denied to prevent exploitation. All of the results after
discovery are reported to administration.
Should the source code for the program be unavailable, the assembler
code will be analyized. This is still theoretical, but analysis of
assembly language for a malicious or vulnerable set of instructions is a
field of research that will yield revolutionary spoils. Analysis of this
scale would be able to detect viruses, overflows, race conditions --
threats to security for the last two decades.
[ This could yield way more than simple source code bugs. It's entirely
possible that a compiler has a bug in it's code-emission routines,
causing bugs that source-code analysis would miss. {ajax} ]
[ An interesting way to audit and possibly rate compilers by the code they
generate. A whole new era of benchmarks :) {kynik} ]
Analysing Nonlinear Data
"When an attacker gathers information, there is a pattern, and we can
detect it."
The Problem
The attacker(s) are trying to gather information about a system; this is
the step prior to an intrusion attempt. The author assumes they are using
distributed attacks for anonymity and stealth.
The Solution
The author's solution is a security daemon that implements a neural
network routine. In short time intervals, the pattern of the frequency
and type of external service requests are compared to two usage pattern
tables in the neural network. These two tables are Normal patterns and
Probing patterns.
[ It's my opinion that you're going to need more than just two pattern
tables here, call me crazy. You are probably going to need several
tables, broken up into logical groups "Normal" and "Probing". {kynik} ]
[ You may also wish to have this security daemon running across your
network, with an NFR-like central analysis point of network traffic. Or
put it in-line between your ethernet hub and your internet connection as
an ethernet bridge and monitor traffic for your whole network at once.
Interesting. {ajax} ]
This method of detection is very feasible because these neural networks
have been used for years to classify nonlinear data, they are effective,
and they can be used to defend computer systems. If the neural network
determines the system is being probed, the following actions may be
taken:
* Notify personnel
* Selectively deny connections
* Close the services
* System shutdown.
I'm sure there are many more actions that can be taken.
Work for this neural network is in the works; after programming for it
is completed, the neural net will need to be "trained" so that the two
tables for normal and probing patterns can be defined. This will simply
involve defining the table to be wrote to, and executing the actions which
fall under the table type upon the system. Once training is complete, the
daemon will be able to grade the intervals of service queries with a
percentage. So as an example, 10% Normal and 90% Probing results would be
(if the NN was trained properly) obvious signs of probing behavior.
***********************************************************************
*** C++ Tutorial : Kynik
***********************************************************************
[ I had this laying around and figured someone out there may want to know
some of this stuff. If not, skip it and life goes on. This was a rough
draft of my application to become the Happy Hacker UNIX Editor, so if it
seems elementary, accept my apologies. I also know that certain
gh0st.net/FS/#osuny people are going to want to flay me alive for some of
the comments I make about C. Be gentle ;) {kynik} ]
Q:
Why is C++ interesting?
A:
While it was C that most UNIX-based utilities were written in (not to
mention the UNIX kernel itself), C++ is (at least in my opinion) simpler
to code than C, and thus easier to pick up on than C. I'll try to show
the equivalent C code (if different) when I give code examples later to
illustrate this issue. My point is, C++ is interesting since it offers a
good way to get programming, and gives you a lot of functionality for a lot
less trouble than C. (and can be used easily by those of you that already
know C)
Q:
Is C++ portable?
A:
While there is an ANSI C++ standard, it's new and not as well-implemented
as the ANSI C standard in most cases. I would argue though, that for the
most part, it is fast, stable, and portable. My reason for this is that
I've written a fairly advanced port scanner using C++, and only minor
modification was needed to use it on a Sun machine after compiling it in
Windows. (Took me all of 10 minutes)
[ Yeah, routine, perl probably would have been simpler yet... {kynik} ]
Q:
I think this C++ thing is just a fad, and will drift away like so much
milkweed. What do you think?
A:
I have a feeling that if C++ was a 'fad' that it would have died out by
now. The Java programming language modeled its syntax after C++, so Bjarne
Stroustrup (the creator) must have been doing something right. Yes,
anything you write in C++ can be written in C, but you can do it in a more
readable fashion, and more legibly. I know all you hardcore C programmers
are firing up your mailbombers at me, but keep in mind this is not the word
of the gods... it's just my opinion, which I tend to feel rather strongly
about.
[ Not that Java is anything terribly great {kynik} ]
Now, a little introduction.
C++ was designed to be a language with (mostly) clearly defined parts, like
your liver, heart, spleen... you get the picture. Each part has its own
particular function that it is very good at. Your liver filters out the
toxins in your body, your heart pumps blood, for example. This is usually
called "Object Oriented Programming" (or OOP for short). As one of my
professors so nicely put it, "C++ is a number of good languages." And
you'll begin to understand why as you get deeper and deeper into the guts
of the language. I'll try to analyze the major focal points of
Object-Oriented programming and C++ here, and give you some more detail
later.
<RUST> (random useless string of trivia)
C++ is an offshoot of the C programming language, so instead of giving it
an entirely new name, Bjarne Stroustrup (the creator) decided on the name
C++. And it's appropriate since the ++ operator in C (and C++) increases
something by one. So you can think of C++ as "C plus one".
</RUST>
The 7.5 steps to programming:
[ Ok, looking back on this, I'm chuckling to myself. I encourage all of
you to laught with/at me too. {kynik} ]
Step 1: Get a computer
If you're reading this document, this step is pretty well taken care of.
Step 2: Get an idea
You must want your computer to do something neat, right? Well, figure out
what that something is. You may want to write it down.
Step 3: Get a compiler
A compiler is a program that allows the computer to take the C++ program
and change it into something it understands, namely binary. (lots of 1s
and 0s) If you have Linux, great! Chances are you have a C++ compiler
already installed on your computer. The cool thing about a C++ compiler
is that you can compile C programs with it too! The most common C++
compiler on a Linux-based computer is g++, the GNU C++ compiler. If you
have a different OS, chances are that g++ supports it as well. Most
UNIX-based operating systems have a version of g++ available, and the
various Windows OSs are supported as well. Check out the following link
to the g++ FAQ:
http://www.cygnus.com/misc/g++FAQ.html
If your OS isn't represented here, either contact the OS manufacturer or
do a quick web search (using altavista.com, for example) for C++ and the
name of your OS.
Step 4: Get a clue
Learn what you can about the progamming language of your choice (in this
case, C++) This tutorial should be a good starting ground for you, but
definitely should not be the last thing you read, if you're interested
in programming. (Hopefully it's not the first, either ;) It is a very good
idea to read the documentation that came with your compiler, too. (To do
this on a Linux box, type man g++) Buy a book or two, or read some free
ones at http://www.mcp.com/personal/
Step 5: Get some time
A program is not something that just will happen by itself. It takes a
certain amount of work. But I'm confident all of you are up to it. Then
you know you have to work for it ;)
Step 6: Crank out the code
Lock yourself in a room with a 12 pack of your beverage of choice and start
writing.
Step 7: Debug
Is the code exactly as it should be? If not, return to step 6. If so, then
look at it again and try to compile. Return to Step 6 when you find an
error. NOTE: The second time you reach Step 6, you may want to switch to
or from a caffeinated beverage, depending on what you started with.
Step .5: Get a Life
Insert this step liberally between all of the others. No, seriously, it's
very important to take an occasional break to avoid frying your brain.
(Graduate with a degree in Comp Sci or work fulltime as a programmer and
you'll understand)
My first C++ program
--------------------
// This is my first C++ program
#include <iostream.h>
main()
{
cout << "Goodbye world!";
}
Copy these few lines starting at the line with the two slashes "//" and
ending at the right brace "}" into a file named goodbye.cc using your
favorite editor. Try pico if you don't know much about editors and you're
using Linux. If you're using Windows, try notepad. The following would be
what you'd use if you were writing this in C. (Not too much difference at
this point)
/* This is my first C++ program (C Style) */
#include <stdio.h>
main()
{
printf("Goodbye, world!");
}
Ok, let's go through this program line by line.
// This is my first C++ program
This line is called a comment. The computer doesn't do anything with this
-- it's entirely for the programmer's benefit. Anything that's on a line
after the double forward slashes is ignored by the compiler. Feel free to
write whatever the heck you want in this space after the //. As a matter of
fact, make a couple more lines of comments if you so desire.
#include <iostream.h>
This is a line that tells the compiler (well, the preprocessor, but that's
not important right now) to insert the contents of the specified file.
This allows you to use pieces of code that have already been created for
your own programs. In this case, the file iostream.h lets us use the
"cout" in a following line of code. Other 'header files', as these are
called, allow you to use different functions, or chunks of code. This
particular header file lets us use things relating to I/O (Input/Output)
streams to display and read text.
main()
This is what is called the main function. This is the place that the
computer starts running the program. The parentheses show that it is a
function, or a block of code for a certain purpose. main's purpose is to
be the starting point for the rest of the program.
{
The left brace shows the beginning of the code in a function.
cout << "Goodbye, world!" << endl;
This simply prints out the string "Goodbye, world!" to the screen.
(without the quotes) "cout" starts everything out, and more or less means
"C output". The double less-than is then used to show that the next part
should be displayed to the screen, which in this case is "Goodbye, world!".
Again, we see the double less-than, but now following them is "endl". This
tells the computer to end the line. (like hitting the Enter key) The
semicolon (;) at the end tells the computer that the line of code is done
and to move on to the next line.
}
The right brace shows the end of the code in a function. Makes sense,
right?
Now, you're not quite done yet. The computer has yet to change this into a
form that it can use. At the moment, the code is really only good for you,
the programmer.
Structs
-------
Ok, I'll admit it, structs aren't unique to C++, they're in C too, but I
thought it was a good place to start this out. struct is short for
structure, which may help you visualize what we're doing a little better.
These structures can contain various data inside. What kind of data, you
ask? Here's a quick example of how to define a struct in C/C++.
struct body
{
arm leftArm;
arm rightArm;
leg leftLeg;
leg rightLeg;
head myHead;
};
No need to panic...we'll get to all of this in time. Basically I just
created an object that works as a container for 5 other objects, in this
case, 2 arms, 2 legs, and a head. (Think Voltron and the lions if you're
old enough to remember it)
struct body
This line creates a struct of type body, so if I ever need a 'body'
object, it's defined here.
{ and }
The braces act as the container for what's inside the 'body' struct.
arm leftArm;
arm rightArm;
:
:
head myHead;
These lines create the actual objects inside the 'body' struct. The first
word there tells what kind of object we have. In the first 2 cases, it's
an arm. (on a side note, the computer must somehow know what an arm, leg
or head is already for this to work) The second word gives the actual name
for this object. This name, also referred to as an identifier, is how we
will access this object when we need to.
The trailing semicolons signify the end of a struct definition, or the end
of a line of code.
So now, if we wanted to create a body object, we would type something like
the following line:
body x;
This creates a body called 'x' in C++. Ok, now the question that pops
into all of your minds at this point is, "How can I get to x's arms, legs
and head." Good question! You do that like this:
x.leftArm
Just add a period and then the name of the object. You could have just as
easily made it x.rightArm or x.myHead, too.
Object Oriented Programming lets us create very modular programs, and
makes it pretty easy to reuse code. But I digress.
Classes
-------
No, this section doesn't mean you have to go back to school. A class is
very much like a struct with a few notable differences. (Ok, there's only
actually one, but that's not important right now) A class can have what
are called 'member functions' which allow you to embed code specific to
that object right inside. A function is simply a piece of code that
performs, get this... some action or function. Classes also bring up
another topic: public members and private members. In a struct, all the
data items you create are 'public'. That is, anyone from the outside can
access them. Picture an open field with data objects lying around.
Anyone can walk in and play with them there. In a class, you have the
option of making a member 'private' so only certain things can play with
it. Now imagine a locked building in the middle of that field. Anyone
can play with the class' public members, but nothing except something
inside the class can access a private member. (Well, this isn't entirely
true either, but for right now it will work)
[ Not entirely true, he says... structs can have member functions, too.
Like he said, there's only one actual difference, which is that *by
default* members of structs are public, whereas in classes by default
members are private. Structs can have private members, too, you just
have to make that explicit. If this confused you, move on. {ajax} ]
[ I was actually leaving out the details of friends, something that I'm
not terribly interested in exploring right now. {kynik} ]
Here is a sample class:
class book
{
public:
section GetChapter(int);
section tableOfContents;
private:
section GetIndex();
section chapter1;
section chapter2;
section chapter3;
section index;
}
See, that's not too much different from the struct I showed above.
class book
This is how we create a class, just like we did with a struct.
{ and }
Same as before.
public:
This says that until further notice, treat everything as a public member.
section GetChapter(int whichOne);
This is a function declaration. The first word is the 'return type'. This
shows what kind of object you're going to get back when you use this
function. The second part is the function name. This is how you'll use
the function. The part in the parentheses is called the parameter list.
This is where you input something into the function to modify its
behavior. In this case, we have one parameter of type 'int'. ('int' is
short for 'integer', which is a non-decimal round number like 1, 56, or
-2) If we had more than one parameter, we would separate them with commas.
In this case, we want the function to return the section object depending
on what we give as the parameter. So if we give the function 1, we want
it to give us chapter1 back, and chapter 2 if we give it a 2, and so on.
We can call a function within a class by using much the same notation as
accessing data.
book z;
z.GetChapter(1);
The second line there would give us the section object chapter1, if we
wrote the function correctly.
section tableOfContents;
This is a public data member. Anyone can play with this.
private:
Just like public:, this specifies that until further notice, all members
are private and overrides the previous public:.
section GetIndex();
This is a private member function and cannot be called outside of the
class. So z.GetIndex() will not work. Also, notice that functions are
allowed to not have parameters. The parentheses must still be included,
however.
section chapter1;
:
:
section index;
These are private data members and can only be accessed from within the
member functions of this class.
If you're a C programmer already, this is probably not too far to stretch
for you right now. The rest of you, rest assured that I will elaborate
more on this in another post. Future topics include inheritance,
templates, streams, and useful coding in C++.
Author's note:
I really don't have much intention of doing any more with this. If there's
anybody out there that thinks they might benefit from me doing more on the
topic, let me know. If not, I'll let this beast die quietly. I promise my
contribution to Napalm 4 won't suck as badly.
***********************************************************************
*** Future Issues
***********************************************************************
Creating Restricted ("Sandboxed") User Accounts : Fict
Firewalls and Censorship : Kynik
***********************************************************************
*** Credits
***********************************************************************
Editor: Kynik <kynik@firest0rm.org>
Co-Editor: ajax <ajax@firest0rm.org>
Article Contributions: c_routine <c_routine@gh0st.net>
snock <snock@snock.raex.com>
Blakboot <blakboot@firest0rm.org>
URL Submissions: hubbo <root@mindsong.net>
***********************************************************************
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