C / C++ / MFC Discussion Boards

Re: Difference between Structures and Classes

Antony M Kancidrowski17-Jun-04 2:09

Antony M Kancidrowski

17-Jun-04 2:09

You can add methods to structures. I can only see that you can't inherit from structures. No polymorphism. Smile | :)

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

Re: Difference between Structures and Classes

Zeeshan Bilal17-Jun-04 2:18

Zeeshan Bilal

17-Jun-04 2:18

it means simply that if we not inherit structures ,,
then we can not attain the Concepts of OOP with structers.. is it.

any other difference ??

thanx

Re: Difference between Structures and Classes

Antony M Kancidrowski17-Jun-04 2:40

Antony M Kancidrowski

17-Jun-04 2:40

I can't think of any other difference.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

Re: Difference between Structures and Classes

David Crow17-Jun-04 3:01

David Crow

17-Jun-04 3:01

Antony M Kancidrowski wrote:
I can only see that you can't inherit from structures.

Have you not seen the CRect class? It is derived from the tagRECT struct. This is perfectly legal:

struct s
{
};
 
class c : public s
{
};

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Difference between Structures and Classes

Antony M Kancidrowski17-Jun-04 10:07

Antony M Kancidrowski

17-Jun-04 10:07

That isn't a struct inheriting from a struct, which is what I meant. Point taken however.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Re: Difference between Structures and Classes

David Crow17-Jun-04 10:11

David Crow

17-Jun-04 10:11

Antony M Kancidrowski wrote:
That isn't a struct inheriting from a struct, which is what I meant.

But this is:

struct s1
{
};
 
struct s2 : public s1
{
};

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: Difference between Structures and Classes

Antony M Kancidrowski17-Jun-04 10:15

Antony M Kancidrowski

17-Jun-04 10:15

OK, I have learnt something new. I have never seen such a struct definition. Noted and commited to memory.

Thanks David

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Re: Difference between Structures and Classes

Maximilien17-Jun-04 2:39

Maximilien

17-Jun-04 2:39

in c++, a class and a struct are the same, except that in the case of a struct, members are public by default, and in a class, members are private by default.

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: Difference between Structures and Classes

V.17-Jun-04 2:48

17-Jun-04 2:48

2)C++ structure and C++ class
Actually, C++ structure and C++ class are very closely realated. With one exception, they are interchangeable because the structure can also include the data, and the code that manipulates that data, in just the same way that a class can. The only difference between a C++ structure and a class is that, by default, the members of a class are private, while the members of a structure are public (This also clears up an error I made in the first lab). Aside from this distinction, structures and classes perform exactly the same function.

Here is an example of a structure that uses its class-like features.

One last point just in case you are curious about it. A structure defines a class type. Thus, a structure is a class. This was intentional on the part of the inventor of C++ -- Bjarne Stroustrup. He believed that if structures and classes were made more or less equivalent, the transition from C to C++ would be eased.

http://www.cs.uregina.ca/links/class-info/210/LabFAQ/

There it is...

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: Difference between Structures and Classes

markkuk17-Jun-04 2:52

markkuk

17-Jun-04 2:52

There's nothing more to tell. In C++ a struct is a class with public access to members and public inheritance by default. They have all the same features.

Re: Difference between Structures and Classes

Navin17-Jun-04 3:03

Navin

17-Jun-04 3:03

Technically, that is the only difference.

From a conceptual standpoint, though, struct is customarily used for entities that just serve as convenient buckets to hold data, where class isused for objects.

"Fish and guests stink in three days." - Benjamin Franlkin

Time required for copying

pavanhere17-Jun-04 1:13

pavanhere

17-Jun-04 1:13

Hi!

I need to know how do i find out the time required to copy a set of files on the disk.

The explorer can tell me how much more time is needed to copy the files. ("35 seconds remaining" kinds).

What are the API's that I can use for this purpose.

Thanks in advance,
Pavan.

Re: Time required for copying

RChin17-Jun-04 1:22

RChin

17-Jun-04 1:22

pavanhere wrote:
What are the API's that I can use for this purpose.

I don't think there is such an API.
I think explorer is dynamically estimating that time, possibly based on transfer speed and file size.

I Dream of Absolute Zero

Re: Time required for copying

Henry miller17-Jun-04 3:15

Henry miller

17-Jun-04 3:15

Explorer seems to count the total number of files remainging, and multiply the time it took for the last file to copy by that. At least that is my only explination for why copy times jump from 45 minutes to 100 minutes back to 50 all the time in long copies.

A better alogrythm would be something like count the bytes done already, the bytes total, and the time used so far. Time remaining = bytes done * time used / total bytes. Or something like that, simple math, but if you don't wish to check and understand the math you shouldn't impliment it. Course this assumes you know the total bytes, which you can count, but that takes time you could use for the copy.

Re: Time required for copying

Blake Miller17-Jun-04 4:08

Blake Miller

17-Jun-04 4:08

On the other hand, if you added up the total bytes first, and examined your destination, you could also offer the user a "all these files won't fit" message, which I sometimes SORELY miss when I started a copy process that is going to take 20 minutes, only to come back and find out the last 50 files did not copy becasue I ran out of disk space or something. So there sometimes is a benefit to operations that might seem to take longer on the front end.

How to start app from inside code??

Anonymous17-Jun-04 1:02

Anonymous

17-Jun-04 1:02

How does one start an app from inside one's code. For example, I have an app called myapp.exe. How do I start it from within a new program. Do I need to bring up an instance of a console and pipe "C:\MyFolder\myapp.exe" to it? Thanks.

Re: How to start app from inside code??

User 665817-Jun-04 1:06

User 6658

17-Jun-04 1:06

ShellExecute

regards

modified 12-Sep-18 21:01pm.

Re: How to start app from inside code??

RChin17-Jun-04 1:11

RChin

17-Jun-04 1:11

read this[^] from the CP FAQ

I Dream of Absolute Zero

Re: How to start app from inside code??

Antony M Kancidrowski17-Jun-04 1:37

Antony M Kancidrowski

17-Jun-04 1:37

CreateProcess() is by far the most useful method IMO

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

get the current working directory

shiva shankar17-Jun-04 0:50

shiva shankar

17-Jun-04 0:50

how to get the current working directory in MFC app Wizard (vc++), i have the code but it is working in Winconsole (vc++),but the same code is not working in MFC app Wizard, is there there any alternative code in MFC app wizard..

//

#include <direct.h>
#include <stdlib.h>
#include <stdio.h>

void GetCurrentPath(char* buffer)
{
getcwd(buffer, _MAX_PATH);
}

void main()
{

char CurrentPath[_MAX_PATH];

GetCurrentPath(CurrentPath);

printf("%s" , CurrentPath) ;//using messagebox instead of printf in mfc it is not working

}

Re: get the current working directory

Dudi Avramov17-Jun-04 0:56

Dudi Avramov

17-Jun-04 0:56

Use GetCurrentDirectory WIN32 API.

Manipulate text file

?!?17-Jun-04 0:47

?!?

17-Jun-04 0:47

Hi I need to open a text file, edit it, then save it with these modifications, how can I ?

Re: Manipulate text file

toxcct17-Jun-04 1:00

toxcct

17-Jun-04 1:00

fopen(<font style="color:gray;">"C:\\folder\\file.txt"</font>, <font style="color:gray;">"a+"</font>);

TOXCCT >>> GEII power

Re: Manipulate text file

V.17-Jun-04 2:02

17-Jun-04 2:02

FILE *handletofile;

handletofile = fopen("pathtofile", "a+"); //open the file

fscanf(handletofile, "%s", string); //for reading
fprintf(handletofile, "%s", string); //for writing

fclose(handletofile); //close file (do not forget!)

fread and fwrite for binary files.

use fseek to set your pointer to a specific place in the file.

do not open in beginning of exec. and close at end. open/close more often to flush the text and to have something in case your program crashes.

Good Luck.

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: Manipulate text file

chauteen25-Aug-04 22:44

chauteen

25-Aug-04 22:44

hi,
Can you say something more about fseek please?
how to use fseek to go to a certain line of a file.
For examlpe, I need to overwrite the thrid line of the file.
But fseek and fgetpos simply moving the file pointer in the same line, not be able to next line.
Thankx.

chauteen

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