RE: Good resource for beginning programmers

  • From: "Ken Perry" <whistler@xxxxxxxxxxxxx>
  • To: <programmingblind@xxxxxxxxxxxxx>
  • Date: Thu, 18 Nov 2010 21:14:43 -0500

Pointers are awesome I have taught them a few times and it's easier to teach
them if you can see because you can have class mates point at each other and
then do a lot of  chaining pointers and pointing people at different papers
etc it makes a whole lot more since that way but I will tell you this once
you get pointers down even languages that profess not to have pointers make
a lot more since because you know what's under the hood and how it works.
So stick with it you will get it.

Ken

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex Midence
Sent: Thursday, November 18, 2010 8:58 PM
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: Good resource for beginning programmers

Oh, I'd already decided on that.  Too many people keep saying things
about this guy's work.  I'm working through Accellerated C++ actually.
 This bit just stuck in my head when I was trying to get my head
around pointers.  I read this because I figured reading different ways
of presenting information might help it click better.  Glad to know
it's incorrect.  I've been somewhat afraid to mess with pointers ever
since I read this for fear of an error or oversight of mine ruining my
pc.

Alex M

On 11/18/10, Littlefield, Tyler <tyler@xxxxxxxxxxxxx> wrote:
> It is not correct. You can screw up your program for sure, but as we
> were talking about: most operating systems lock you in your own memory.
> You'll just crash that program if you mess with a dangling pointer. A
> dangling pointer is a pointer that doesn't doesn't point to anything
> -you- allocated. So: a pointer on initialization or a pointer after you
> call delete on it, but don't set it to NULL. As a side note, I recommend
> you find a new book.
> On 11/18/2010 6:39 PM, Alex Midence wrote:
>> Hi, Tyler,
>>
>> I wasn't trying to scare anyone.  I was trying to explain how much
>> more low level c or c++ could be than something lie php or python.  As
>> for whether or not pointers are dangerous.  Here's something I read
>> recently.  It's exerpted from the book c++ from the ground up 3rd
>> edition by Herbert Schildt chapter 6 page 121:
>>
>> "The Null Pointer Convention
>> After a pointer is declared, but before it has been assigned a value, it
>> will
>> contain an arbitrary value. Should you try to use the pointer prior to
>> giving
>> it a value, you will probably crash not only your program, but perhaps
>> even
>> the operating system of your computer (a very nasty type of error!).
While
>> there is no sure way to avoid using an uninitialized pointer, C++
>> programmers
>> have adopted a procedure that helps prevent some errors. By convention,
if
>> a
>> pointer contains the null (zero) value, it is assumed to point to
nothing.
>> Thus, if all unused pointers are given the null value and you avoid the
>> use of
>> a null pointer, you can avoid the accidental misuse of an uninitialized
>> pointer. This is a good practice to follow. Any type of pointer can be
>> initialized to null when it is declared. For example, the following
>> initializes p to null:
>> float *p = 0; // p is now a null pointer
>>
>> To check for a null pointer, use an if statement, like one of these:
>> if(p) // succeeds if p is not null if(!p) // succeeds if p is null
>>
>> If you follow the null pointer convention, you will avoid many problems
>> when
>> using pointers."
>>
>> Clearly, you  have to be careful using pointers or you might do some
>> damage. That's all I was trying to convey.  Now, the big question is
>> this:  This particular author has been heavily criticized due to a
>> book he wrote about fifteen eyars ago about C which has since
>> undergone quite a few revisions.  Is this information I am quoting
>> correct or not?
>>
>> Thanks.
>> Alex M
>>
>>
>>
>>
>>
>> On 11/18/10, Littlefield, Tyler<tyler@xxxxxxxxxxxxx>  wrote:
>>> Awesome. Well, the point was to keep the OP from getting scared away
>>> from c++ in the thought that as alix posted, you could ruen your
>>> harddrive, bla bla. On another note, I am kind of curious about some of
>>> these attacks you talked about. Is there a good place to learn about
>>> them? I can understand the page fault handler; I'd assume you'd just do
>>> whatever you want then call the one before or whatever, but I'd like to
>>> learn a lot more of the theory behind the attacks, try the code on a box
>>> that I can afford to crash a time or 10, etc.
>>>
>>> On 11/18/2010 1:31 PM, Sina Bahram wrote:
>>>> Oh for sure.
>>>>
>>>> Otherwise, all you're going to do is simply crash your own program.
It's
>>>> hard to even get a old fashioned blue screen anymore, much
>>>> less accidentally corrupt someone else's address space.
>>>>
>>>> Take care,
>>>> Sina
>>>>
>>>> -----Original Message-----
>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of
Littlefield,
>>>> Tyler
>>>> Sent: Thursday, November 18, 2010 3:28 PM
>>>> To: programmingblind@xxxxxxxxxxxxx
>>>> Subject: Re: Good resource for beginning programmers
>>>>
>>>> Hahaha. That sounds fun. I guess the point I'm trying to make: you have
>>>> to
>>>> intentionally try to get to this point. You can do these
>>>> lovely things, but in order to get there, you have to knowingly
escolate
>>>> privileges, inject code, whatever.
>>>> On 11/18/2010 1:24 PM, Sina Bahram wrote:
>>>>> Nope, none of them require API's.
>>>>>
>>>>> You can do some really weird things with privilege escalation, and
>>>>> then it's all over. Jump to lib attacks, return oriented programming,
>>>>> jump oriented programming, basic stack smashing, basic heap overflows,
>>>>> dll injection, ring -1, -2, and -3 level attacks depending
>>>> on virtualization technologies being used, page table corruption
>>>> attacks,
>>>> chain of trust invalidation, etc, etc, etc.
>>>>> That's only the latest stuff. You'd be amazed how many attacks from
>>>>> pre 2005 still work. For example, you overwrite the interrupt
>>>>> descriptor table, grab some debug registers, point one of them at your
>>>>> page fault exception handler, and it's over ... There is no
>>>> way to detect that sucker, no matter how good your antivirus is.
>>>>> Take care,
>>>>> Sina
>>>>>
>>>>> -----Original Message-----
>>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of
>>>>> Littlefield, Tyler
>>>>> Sent: Thursday, November 18, 2010 3:18 PM
>>>>> To: programmingblind@xxxxxxxxxxxxx
>>>>> Subject: Re: Good resource for beginning programmers
>>>>>
>>>>> Well, you need to go through an API usually, no? It's not going to
>>>>> happen
>>>>> with a dangling pointer in a normal app.
>>>>> On 11/18/2010 1:16 PM, Sina Bahram wrote:
>>>>>> Not hard at all, just minorly annoying.
>>>>>>
>>>>>> Take care,
>>>>>> Sina
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of
>>>>>> Littlefield, Tyler
>>>>>> Sent: Thursday, November 18, 2010 3:04 PM
>>>>>> To: programmingblind@xxxxxxxxxxxxx
>>>>>> Subject: Re: Good resource for beginning programmers
>>>>>>
>>>>>> That's what I was getting at; the whole virtual addressing and stuff.
>>>>>> He
>>>>>> was making it sound as if:
>>>>>> int i[10]
>>>>>> i[10]=300
>>>>>> Was going to make things go boom. :) I jus didn't want the OP to be
>>>>>> scared off. Windows and *nix both have virtual addressing, so
>>>>>> accessing
>>>>>> bob's process from joe's process is fairly hard.
>>>>>> On 11/18/2010 12:57 PM, qubit wrote:
>>>>>>> Hi Ty -- I am not sure about windows so take this with a grain of
>>>>>>> salt, but it is true that an OS does have some protections, such as
>>>>>>> preventing writing to someone else's virtual memory, to guard
>>>>>>> against malware.  However a truely pathological C++ program can use
>>>>>>> pointers to do some interesting things with stack frames that will
>>>>>>> cause a lot of very strange behavior.
>>>>>>> But no, it won't go outside the process's virtual space,
fortunately.
>>>>>>> And perhaps it varies with the OS.
>>>>>>> Keep in mind though that a debugger is just a program, and needs to
>>>>>>> have the ability to control a process and therefore needs to be able
>>>>>>> to write to addresses that are otherwise protected.
>>>>>>> I particularly enjoyed debugger development when I was working in
>>>>>>> language support.  It is fascinating to me to see how a process is
>>>>>>> implemented.
>>>>>>> --le
>>>>>>>
>>>>>>> ----- Original Message -----
>>>>>>> From: "Littlefield, Tyler"<tyler@xxxxxxxxxxxxx>
>>>>>>> To:<programmingblind@xxxxxxxxxxxxx>
>>>>>>> Sent: Wednesday, November 17, 2010 7:32 PM
>>>>>>> Subject: Re: Good resource for beginning programmers
>>>>>>>
>>>>>>>
>>>>>>> You're making c++ sound way way to dangerous. If you mess up with a
>>>>>>> pointer, unless you're programming at a way way low level and
>>>>>>> directly accessing the harddrive, you're not going to trash
anything.
>>>>>>> You have access to memory, but like I said before when you went off
>>>>>>> on this "c++ can blow up the world," thing, the OS protects
>>>>>>> programmers from themselves. Or sort of, anyway.
>>>>>>> On 11/17/2010 6:20 PM, Alex Midence wrote:
>>>>>>>> Good lord, no!  php might be written in c++ but, I promise you that
>>>>>>>> you can not do the same things.  Php won't have stuff like template
>>>>>>>> metaprogramming, generic programming nor will it compile right down
>>>>>>>> to binary like c++.  If you write stuff in c++, it runs lightning
>>>>>>>> fast.
>>>>>>>> I don't know the syntax to php but, I'm pretty sure it's too
>>>>>>>> different from c++ to be concsidered a dialect.  Python is
>>>>>>>> definitely nothing like c in its syntax.  And, you could never
>>>>>>>> program a driver in Python.  It would take forever if it runs at
>>>>>>>> all.  They are not dialects of the languages they are written in.
>>>>>>>> I wish someone who was a bonified computer scientist could jump in
>>>>>>>> and explain this in terms more fitting.  Scripting languages are
>>>>>>>> used
>>>>>>>> primarily for tweaking.
>>>>>>>> Look at the Jaws scripting language, for instance.  Languages like
>>>>>>>> Python and lua are used to customize applicatiosn written in stuff
>>>>>>>> like c++ so that they don't have to rewrite the whole app and
>>>>>>>> recompile it just for a few modifications.  It's hard to explain.
>>>>>>>> Honestly, you will just have to do some research until you find
>>>>>>>> something that explains it to you in a way that will make sense to
>>>>>>>> you.
>>>>>>>>
>>>>>>>> Yes, the lines between some scripting languages and programming
>>>>>>>> languages are becoming blurred but the great yawning chasm that
>>>>>>>> will never be crossed is still the interpreted versus compiled
>>>>>>>> chasm.
>>>>>>>> You might technically be able to write an application from the
>>>>>>>> ground up in pure Python but, I promise you that if that thing goes
>>>>>>>> toe to toe with another version of the same application written in
>>>>>>>> c++, it will lose every time.  By the time the Python app is done
>>>>>>>> printing out its welcome message, the c++ app has done what was
>>>>>>>> asked
>>>>>>>> of it and closed.
>>>>>>>>        This is because there are too many layers between the app
and
>>>>>>>> the binary code for it.  It's first got to go through the
>>>>>>>> interpreter which then puts it into binary.  The app written in c++
>>>>>>>> runs right on the system itself.  You have to go to something like
>>>>>>>> c or asm to get lower level.  The isntructions to the computer
>>>>>>>> don't have to be translated before execution.  The day when what
>>>>>>>> you mention with regard to making something like c++ available to
>>>>>>>> the nonprogrammer is way way far off in the future if it will ever
>>>>>>>> come.
>>>>>>>> I frandkly hope it doesn't  The thought of some nonprogrammers I
>>>>>>>> know with acces to that kind of computing power is frightening.  I
>>>>>>>> mean, you can tell the computer exactly what to do right down to
>>>>>>>> what goes where in each individual piece of memory.  There are no
>>>>>>>> shortcuts in that language.
>>>>>>>> And, there shouldn't be.  It gives you so many chances to shoot
>>>>>>>> yourself in the foot that if you aren't down in the inner workings
>>>>>>>> of it, as it were, under the proverbial hood, you won't be able to
>>>>>>>> control what it does.  You could realistically totally trash a hard
>>>>>>>> drive if you screw up just right with pointers and if you do
>>>>>>>> something like overflowing an array of 10 items with say 100 or
>>>>>>>> something like that.  I hear you can do some serious damage with
>>>>>>>> stuff
>>>>>>>> like that.
>>>>>>>> Can't see that kind of damage being caused by php or python.
>>>>>>>>
>>>>>>>> Alex M
>>>>>>>>
>>>>>>>> On 11/17/10, Client Services<operations@xxxxxxxxxxxxxxx>
>>>>>>>> wrote:
>>>>>>>>> Hi-
>>>>>>>>> Thank you for that explanation.
>>>>>>>>> Seems like the line between programming and scripting languages is
>>>>>>>>> getting blurred.
>>>>>>>>> Are scripting languages becoming as powerful as a programming
>>>>>>>>> language?
>>>>>>>>> Or
>>>>>>>>> do they just bring the best out of the programming language they
>>>>>>>>> are written in.
>>>>>>>>> If PHP and Python are written in C and C++, then why can't they
>>>>>>>>> make PHP and Python to be more like a CMS and useable by
>>>>>>>>> non-programmers?
>>>>>>>>> In summary, if I have this correct, a scripting language is
>>>>>>>>> actually written in a programming language and is just a way of
>>>>>>>>> accessing and using the given programming language.
>>>>>>>>> When I use PHP and Python, I am actually using C and C++, just in
>>>>>>>>> a unique dialect?  That is assuming Python and PHP are written in
>>>>>>>>> C or
>>>>>>>>> C++.
>>>>>>>>> So somehow, PHP and Python were supposed to make C or what ever
>>>>>>>>> programming language easier to use?
>>>>>>>>> Is this accurate?
>>>>>>>>> Sorry for the dumb questions.
>>>>>>>>>
>>>>>>>>> H.R. Soltani
>>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>>>>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of
>>>>>>>>> Christopher
>>>>>>>>> Sent: Wednesday, November 17, 2010 6:24 PM
>>>>>>>>> To: programmingblind@xxxxxxxxxxxxx
>>>>>>>>> Subject: Re: Good resource for beginning programmers
>>>>>>>>>
>>>>>>>>> This is one of my pet peeves.
>>>>>>>>>
>>>>>>>>> A programming language is a language that is, in the majority of
>>>>>>>>> the cases, compiled to native machine code -and- used for
>>>>>>>>> application development (i.e. C, C++, D) A scripting language is a
>>>>>>>>> language that is, in the majority of the cases, interpreted -and-
>>>>>>>>> used to control applications, and sometimes application
development
>>>>>>>>> in general (i.e.
>>>>>>>>> Python, PHP, Ruby, AutoIT, etc.) Java was not a true programming
>>>>>>>>> language until recently when it decided to compile its bytecode
>>>>>>>>> on-the-fly. C# has always been a programming language because it
>>>>>>>>> has always compiled its MSIL on-the-fly. PHP and Python are both
>>>>>>>>> written in C and are both interpreted. (PHP might be written in
>>>>>>>>> C++.)
>>>>>>>>>
>>>>>>>>> I refuse to call a non-compiled language a programming language,
>>>>>>>>> regardless of the language.
>>>>>>>>>
>>>>>>>>> So, here is a simple test to see what is a programming language
>>>>>>>>> and what is a scripting language.
>>>>>>>>>
>>>>>>>>> 1. Can you write a full application in the language? If yes, then
>>>>>>>>> is the language compiled? If yes, then it is a programming
>>>>>>>>> language.
>>>>>>>>> 2. Can you write a full application in the language? If yes, then
>>>>>>>>> is the language compiled? If no, then it is a scripting language.
>>>>>>>>> 3. Can you write a full application in the language? If no, then
>>>>>>>>> it is a scripting language.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 11/17/2010 2:24 PM, Alex Midence wrote:
>>>>>>>>>> I am not at a stage in my learning where I can do well at
>>>>>>>>>> explaining this so, I have provided some links for you to
explore:
>>>>>>>>>>
>>>>>>>>>> Scripting language
>>>>>>>>>> http://en.wikipedia.org/wiki/Scripting_language
>>>>>>>>>>
>>>>>>>>>> Programming language:
>>>>>>>>>>
>>>>>>>>>> http://en.wikipedia.org/wiki/Programming_language
>>>>>>>>>>
>>>>>>>>>> Be warned:  This will create more questions for you.  Have fun!!!
>>>>>>>>>>
>>>>>>>>>> Alex M
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 11/17/10, Client Services<operations@xxxxxxxxxxxxxxx>
>>>>>>>>>> wrote:
>>>>>>>>>>> Hi-
>>>>>>>>>>> What is the difference between a scripting language and a
>>>>>>>>>>> programming language?
>>>>>>>>>>> So if PHP and Python are scripting languages, what programming
>>>>>>>>>>> language
>>>>>>>>> are
>>>>>>>>>>> they written in?
>>>>>>>>>>> And why are they called scripting languages?
>>>>>>>>>>>
>>>>>>>>>>> H.R. Soltani
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> -----Original Message-----
>>>>>>>>>>> From: programmingblind-bounce@xxxxxxxxxxxxx
>>>>>>>>>>> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex
>>>>>>>>>>> Midence
>>>>>>>>>>> Sent: Wednesday, November 17, 2010 3:52 PM
>>>>>>>>>>> To: programmingblind@xxxxxxxxxxxxx
>>>>>>>>>>> Subject: Re: Good resource for beginning programmers
>>>>>>>>>>>
>>>>>>>>>>> You've got scripting languages and programming languages there.
>>>>>>>>>>> Javascript is client side scripting.  Websites run scripts on
>>>>>>>>>>> the visitor's machine to dynamically change themselves according
>>>>>>>>>>> to stimuli.  Php is a scripting language that does dynamic
>>>>>>>>>>> webpage changing among other things from the server side.  It is
>>>>>>>>>>> used in conjunction with database solutions like my sql and the
>>>>>>>>>>> like.
>>>>>>>>>>> Java and C are both programming languages.  Java is a high level
>>>>>>>>>>> object-oriented language that runs on a virtual machine.  It is
>>>>>>>>>>> used to create applets and web apps for all sorts of functions.
>>>>>>>>>>> Java is also used to create desktop  applicaitons like, for
>>>>>>>>>>> instance, Eclipse, Open Office, and things of that nature.  C is
>>>>>>>>>>> a low-level procedural programming language that is used for
>>>>>>>>>>> desktop aplications and low-level programming such as drivers,
>>>>>>>>>>> utilities and the like.
>>>>>>>>>>> Certain platforms are also written in C like, for instance,
>>>>>>>>>>> Windoes is in C.  I believe Gnome was also written in C.  I went
>>>>>>>>>>> into this detail because your post indicated that you thought
>>>>>>>>>>> these were all web development languages and they are not.
>>>>>>>>>>> Python is a scripting language that can do a lot of the same
>>>>>>>>>>> things programming languages can do and has a reputation for
>>>>>>>>>>> being easy to learn and fostering rapid development.  An
>>>>>>>>>>> applications that php could not create, IMHO is a screen reader.
>>>>>>>>>>> Python was used to create two of them.
>>>>>>>>>>>
>>>>>>>>>>> Hope that helps,
>>>>>>>>>>> Alex M
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On 11/17/10, Client Services<operations@xxxxxxxxxxxxxxx>
>>>>>>>>>>> wrote:
>>>>>>>>>>>> Hi everybody-
>>>>>>>>>>>> I am trying to decide where to start as far as learning
>>>>>>>>>>>> programming.
>>>>>>>>>>>> I decided I would focus on 1. PHP, 2. JavaScript, 3. Java, 4. C
>>>>>>>>>>>> I figured these are being used the most in web development and
>>>>>>>>>>>> custom applications. So, where does Python come in?  How would
>>>>>>>>>>>> you compare
>>>>>>>>> Python
>>>>>>>>>>>> with Java, PHP, and C??
>>>>>>>>>>>> Can anybody give me an example of what cannot be developed in
>>>>>>>>>>>> PHP which
>>>>>>>>>>> can
>>>>>>>>>>>> be developed in Python?
>>>>>>>>>>>> Or how about Java vs Python if PHP is to lowly?  I have just
>>>>>>>>>>>> heard PHP
>>>>>>>>> has
>>>>>>>>>>>> limitations.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> H.R. Soltani
>>>>>>>>>>> __________
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>>>
>>> --
>>>
>>> Thanks,
>>> Ty
>>>
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>>>
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>
>
> --
>
> Thanks,
> Ty
>
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