Re: Trying to convert int to a char - C / C++ / MFC Discussion Boards

vgrigor20-Feb-04 6:09

20-Feb-04 6:09

For more fun:

I have two dialogs,
inherited wrom one immediate paent,
one works as needed but second is not.

Installation code is simple,

(I have all code).

Re: How to make ClientEdge at CDialog?

Prakash Nadar20-Feb-04 13:01

Prakash Nadar

20-Feb-04 13:01

well, i cant give you a solution for this.

Any way check wheather the initialization is failing or not for the second dialog.

"When death smiles at you, only thing you can do is smile back at it" - Russel Crowe (Gladiator)

Trying to convert int to a char

elvis890020-Feb-04 2:50

elvis8900

20-Feb-04 2:50

I am trying to get a int varibale into a char variable. any help here?

int temp = 20;
char *demo = (char) temp;

Re: Trying to convert int to a char

Anonymous20-Feb-04 2:55

Anonymous

20-Feb-04 2:55

int temp =20;
char demo =(char) temp; // failed if temp > 128

Re: Trying to convert int to a char

elvis890020-Feb-04 3:08

elvis8900

20-Feb-04 3:08

Failed if temp >128?

what does it mean the addressing or the value?

Re: Trying to convert int to a char

J.B.20-Feb-04 3:30

J.B.

20-Feb-04 3:30

elvis8900 wrote:
what does it mean the addressing or the value?

I believe it's the value.

(signed) char holds number from -127 to 128, due to its nature of 8-bit capacity (2^8).

Re: Trying to convert int to a char

Tim Smith20-Feb-04 4:23

Tim Smith

20-Feb-04 4:23

-128 to 127. Smile | :)

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Trying to convert int to a char

Nirav Doshi20-Feb-04 4:22

Nirav Doshi

20-Feb-04 4:22

As a signed char is a 1 byte value (Range: -128 to 127), it can be used to hold values only within the range. The most significant bit (MSB) of the char variable is used to denote a negative or a positive value stored in it. If the MSB is ON (1), it means a negative value stored in the 7 bits remaining.

An unsigned char, on the other hand, can hold values ranging from 0 to 255.

An int is a 2 byte value (N.B.: In a 32-bit platform, it is a 4-byte value). Whichever way, if you're trying to store an int in a char variable, it will ONLY store the first byte (because char can only have a byte).

That means, if:

int n = 50;         //
char c = (char) n;  // This will properly store 50 in the variable c

But, if:

int n = 300;  // If you convert this to binary, you will get two (or four) bytes as 1 & 44 (or 0, 0, 1 & 44)
              // 300 = 00000001 00101100
char c = (char) n;  // This will only get the 1st byte, which will be 00101100, which will be 44

I hope this explains in detail.

Nirav

* Don't wish it was easier, wish you were better! *

Memory handling?

wallyka20-Feb-04 2:13

wallyka

20-Feb-04 2:13

Hello everyone.....

Could someone help me to find a suitable book for memory handling in MS Visual C++? I'm also interested about I/O handling.

Thx,

(w)

Re: Memory handling?

John M. Drescher20-Feb-04 2:40

John M. Drescher

20-Feb-04 2:40

wallyka wrote:
find a suitable book for memory handling

Do you have a specific project in mind? Will you need to handle a lot of memory (> 1 GB)?

John

Re: Memory handling?

Nirav Doshi20-Feb-04 4:05

Nirav Doshi

20-Feb-04 4:05

An excellent book I would recommend to have, is:

* Programming Applications for Microsoft Windows
- By Jeffrey Richter
- Microsoft Press.

* Don't wish it was easier, wish you were better! *

'core dump' on windows

roel_20-Feb-04 2:09

roel_

20-Feb-04 2:09

Hi,

Is it possible like on Unix to have a program dump a file with a stack trace for ease of debugging? If so, how? Thanks.

Re: 'core dump' on windows

Prakash Nadar20-Feb-04 6:02

Prakash Nadar

20-Feb-04 6:02

Yeah visual studio also has something like it. When you are debuging a application and you come with an exception, you click on retry and select debug/view/stack

"When death smiles at you, only thing you can do is smile back at it" - Russel Crowe (Gladiator)

Visual .NET 2003 equivalent of .bsc file

Franz Klein20-Feb-04 2:01

Franz Klein

20-Feb-04 2:01

Is there a Visual .NET 2003 equivalent of the .bsc file found in Visual C++ ver 6?

Smile | :)

I am the handsome one in the crowd.

Multiplexing video capture card

carlomagno20-Feb-04 1:21

carlomagno

20-Feb-04 1:21

I'm a VB developer and i'm making a software that use a multiport video capture card.
I need to use directshow in order to select the video composite-in. I know i need to use the crossbar filter but i'm a novice in c++ programing.
Please help me to resolve my problem.

Thanks

Funny C++

Almindra20-Feb-04 0:27

Almindra

20-Feb-04 0:27

Who can explain :

char *m="az";

cout << m << endl;

i=0;
cout << m[i++] << m[i++] << endl ;

i=0;
((cout.operator<<(m[i++])).operator <<( m[i++])).operator <<(endl) ;

Gives (Visual C++) 6.0 :
az
za
za

Thanks .

Re: Funny C++

David Crow20-Feb-04 3:12

David Crow

20-Feb-04 3:12

Using more than one ++ or -- operator on anything but a line by themselves is always risky. Looking at the statement:

cout << m[i++] << m[i++] << endl;

the i++ statement gets executed first, and that value (1) is used with the [] operator.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Re: Funny C++

Almindra20-Feb-04 4:21

Almindra

20-Feb-04 4:21

sorry but the value of i used by the [] operator will be 0 ...
I think you're confused whith ++i ...

Re: Funny C++

David Crow20-Feb-04 4:40

David Crow

20-Feb-04 4:40

cout << i++ << i++ << endl;

Stepping into the code for ostream& ostream::operator<<(int n) revealed that n had a value of 1 the first time, and a value of 0 the second time. Had the pre-increment operator been used instead, a subscript-out-of-range error would have been realized since the value of n would have been 2 the first time through. Separating the i++ operations into two statements solves all the problems.

"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)

Re: Funny C++

Tim Smith20-Feb-04 4:31

Tim Smith

20-Feb-04 4:31

Um, no.

The problem here is the undefined behavior of the multiple ++ operations which does get you into some problems.

int i = 0;
cout << m[i++] << endl;

This code would fetch the 0'th value. The ++ and -- operators are not risky when you know how to use them. They have well defined behaviors and undefined behaviors.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Funny C++

jbarton20-Feb-04 3:22

jbarton

20-Feb-04 3:22

In the second and third cout statements, you are modifying the value of i more than 1 time between sequence points. The result of this is undefined behavior - the compiler can output anything it wants.

how to open file

Goh Hui Beng20-Feb-04 0:24

Goh Hui Beng

20-Feb-04 0:24

// Loading bitmap image from file
bool ResLoad = SrcImage.LoadBMP24Image(szFileName);

Does anyone knows how this statement actualy loads the file?<br />
Below is the function for it i think

bool CBMPImage::LoadBMP24Image(const char* szFileName)
{

FILE* bmp = fopen (szFileName,"rb");
if (!bmp) return false;

BITMAPFILEHEADER BMPFileHeader;
BITMAPINFOHEADER BMPHeader;
fread (&BMPFileHeader,sizeof(BITMAPFILEHEADER),1,bmp);
fread (&BMPHeader,sizeof(BITMAPINFOHEADER),1,bmp);

if (BMPFileHeader.bfType != 0x4d42) {fclose (bmp); return false;}
if (BMPHeader.biSize != sizeof(BITMAPINFOHEADER)) {fclose (bmp); return false;}
if (BMPHeader.biPlanes != 1) {fclose (bmp); return false;}
if (BMPHeader.biCompression != BI_RGB) {fclose (bmp); return false;}

unsigned long BitColor = BMPHeader.biBitCount;

Re: how to open file

rw10420-Feb-04 1:56

rw104

20-Feb-04 1:56

Goh,
Hope this helps...

FILE* bmp = fopen (szFileName,"rb"); // creates a FILE pointer szFileName
is char[] containing the file name that is passed to the operation.

if (!bmp) return false;//if null e.g no file found

BITMAPFILEHEADER BMPFileHeader;//create handles for the file
BITMAPINFOHEADER BMPHeader;

//fread does the actual loading
fread (&BMPFileHeader,sizeof(BITMAPFILEHEADER),1,bmp);
fread (&BMPHeader,sizeof(BITMAPINFOHEADER),1,bmp);

//check for valid headers date etc..
if (BMPFileHeader.bfType != 0x4d42) {fclose (bmp); return false;}
if (BMPHeader.biSize != sizeof(BITMAPINFOHEADER)) {fclose (bmp); return false;}
if (BMPHeader.biPlanes != 1) {fclose (bmp); return false;}
if (BMPHeader.biCompression != BI_RGB) {fclose (bmp); return false;}

unsigned long BitColor = BMPHeader.biBitCount;

so if success bmp contains a pointer to the bitmap file.

Does this help???? or do you need more info, not sure of your experience etc..
Big Grin | :-D

Ross W

Re: how to open file

Goh Hui Beng20-Feb-04 5:20

Goh Hui Beng

20-Feb-04 5:20

I am a beginner trying to understand the codes

so where does the function knoe which file to create a file pointer. Where should the filename be placed

Thank alot

Re: how to open file

rw10420-Feb-04 5:44

rw104

20-Feb-04 5:44

The key is szFilename, this will be a character array (string)
that will contain the path of the physical file, like "c:\SomeBitmap.bmp" look for the definition of szFilename
before the call below:

bool ResLoad = SrcImage.LoadBMP24Image(szFileName);

It may well of come from a dialog in which case it would have come from a member variable...

The key thing is that you could simply do this:
bool ResLoad = SrcImage.LoadBMP24Image("c:\\SomeBitmap.bmp");

If there is anything else please ask
Smile | :)

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