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Apologies for the shouting but this is important.
When answering a question please:
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Insults, slap-downs and sarcasm aren't welcome. Let's work to help developers, not make them feel stupid.
cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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For those new to message boards please try to follow a few simple rules when posting your question.- Choose the correct forum for your message. Posting a VB.NET question in the C++ forum will end in tears.
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cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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i wanna ask, can anyone suggest any good tutorials references for learning C from the beginning, especially for the latest C version (C17, afaik) ?
refs can be web, e-books, or anything
note:
i tried google. found no tutorials for this.
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C is a rather stable language, every standard doesn't add so many features like happens, for instance, with C++, so you may find (of the tons available) a good tutorial on a previous version (e.g. C99 or C11) and start learning. Then, in order to complete your knowledge, you may access the freely available 'final draft of the standard' (external link in the very wikipedia page: C17 (C standard revision) - Wikipedia[^].
"In testa che avete, Signor di Ceprano?"
-- Rigoletto
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I was trying to use win API GetComputerObjectNameW as below but I am getting error. Can someone help me.
#include <iostream>
#include <atlbase.h>
#include <secext.h>
typedef enum {
NameUnknown,
NameFullyQualifiedDN,
NameSamCompatible,
NameDisplay,
NameUniqueId,
NameCanonical,
NameUserPrincipal,
NameCanonicalEx,
NameServicePrincipal,
NameDnsDomain,
NameGivenName,
NameSurname
} EXTENDED_NAME_FORMAT, *PEXTENDED_NAME_FORMAT;
int main()
{
EXTENDED_NAME_FORMAT enf = NameFullyQualifiedDN;
LPWSTR pwszComputerName;
DWORD dwLen;
dwLen = 0;
GetComputerObjectNameW(enf, NULL, &dwLen);
pwszComputerName = new WCHAR[dwLen + 1];
if(NULL == pwszComputerName)
{
return 0;
}
if(!GetComputerObjectNameW(NameSamCompatible, pwszComputerName, &dwLen))
{
delete pwszComputerName;
return 0;
}
sbstrTrustee = pwszComputerName;
wprintf(L"GetComputerObjectName: %s\n", pwszComputerName);
delete pwszComputerName;
}
Some of Error message is as below.
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(117): error C2146: syntax error: missing ';' before identifier 'GetUserNameExA'
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(121): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(126): error C2086: 'BOOLEAN SEC_ENTRY': redefinition
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(117): note: see declaration of 'SEC_ENTRY'
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(126): error C2146: syntax error: missing ';' before identifier 'GetUserNameExW'
C:\Program Files (x86)\Windows Kits\8.1\include\\shared\secext.h(130): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
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Why do you redefine the EXTENDED_NAME_FORMAT enumeration? 
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I first try without defining enum after that try with enum. In both case I am getting compilation error.
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Add these definition:
#define _WIN32_WINNT 0x0500
#define SECURITY_WIN32
Remove the redefinition of enum.
Define the sbstrTrustee variable.
// edited: also don't forget to include the Secur32.lib library.
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Hi Victor,
I have modified program according to your suggestion but I am not getting expected result. I want to use NameFullyQualifiedDN enum value and get the fully qualified distinguished name (for example, CN=Jeff Smith,OU=Users,DC=Engineering,DC=Microsoft,DC=Com).
Regards,
Rajnesh
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Sorry, I don't know what is wrong/correct in your test.
I've just tested your code and got the result in the form:
[my_domain_name].[my_computer_name]$
wich is in my case 100% correct.
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Good morning,
You are including the wrong header. Remove secext.h and add:
#include <Security.h> The error message is telling you that it doesn't know the definition of SEC_ENTRY.
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Hi All,
//program to place even numbers in one array and odd numbers in another array
PFA code.
#include<stdio.h>
void main()
{
int array[20],array1[20],array2[20],i,n,j;
printf("enter how many array elements\n");
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf("%d",&array[i]);
="" }
="" ***************even="" odd="" in="" array="" elements***************=""
for(i="0;i<n;i++)
{
" if(array[i]%2="=0)
"
="" {
="" array1[i]="array[i];//even" array
="" }
="" else
="" array2[i]="array[i];//odd"
}
="" ******************printing="" elements)*********="" for(i="0;i<n;i++)
" printf("="" even="" is:%d\n",array1[i]);="" printing="" array
}
printf("\n");
for(j="0;j<n;j++)
{
" is="" :%d\n",array2[j]);="" array
}
}
="" output="" what="" i="" got:
enter="" how="" many="" elements
5
1
2
3
4
5
="" is:1970776="" to="" avoid="" this="" is:2
="" is:-1968723210="" my="" output
="" is:4
="" is:4202864="" this
="" :1
=""  ="" am="" getting="" :3
="" :32762="" why="" addresss="" junl="" value
="" :5
--------------------------------
process="" exited="" after="" 7.24="" seconds="" with="" return="" value="" 5
press="" any="" key="" continue="" .="" .<="" pre="">
modified 18-Feb-21 0:51am.
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You are putting holes in your arrays of even and odd elements. In order to avoid that, you need to maintain two separate variables to keep track of how many even and odd items have been added so far. Try
#include <stdio.h>
#define SIZE 20
int main()
{
int items, odd_items, even_items;
int array[SIZE], odd[SIZE], even[SIZE];
printf("enter how many array elements\n");
scanf("%d",&items);
odd_items = even_items = 0;
for (int n=0; n<items; ++n)
{
printf("enter item %d:\n", n);
scanf("%d", &array[n]);
if ( (array[n] % 2) == 0)
{
even[even_items] = array[n];
++even_items;
}
else
{
odd[odd_items] = array[n];
++odd_items;
}
}
printf("array items\n");
for (int n=0; n<items; ++n)
printf("%d ", array[n]);
printf("\n");
printf("even array items\n");
for (int n=0; n<even_items; ++n)
printf("%d ", even[n]);
printf("\n");
printf("odd array items\n");
for (int n=0; n<odd_items; ++n)
printf("%d ", odd[n]);
printf("\n");
return 0;
}
"In testa che avete, Signor di Ceprano?"
-- Rigoletto
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5, but you should get 10 for looking at code formatted this way. 
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Thank you.
"In testa che avete, Signor di Ceprano?"
-- Rigoletto
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Hi,
#include<stdio.h>
int main()
{
char str[20] = "Hello";
char *const p=str;
*p='M';
printf("%s\n", str);
return 0;
}
output:
Mello
As per my knowledge when we use const then we can't change a char in t then how output is Mello instead of Hello.
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You need to read the declaration right to left:
char *const p=str;
| | | |
| | | +- the variable p
| | +----- is a constant
| +---------pointer
+------------to a character
So const here applies to the pointer p and not to the data that it is pointing to. That would be:
const char* p=str;
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Hi Richard,
Thank you for your reply. I understood the concept clearly.
Best Regards
Niharika
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const applies to what's on its immediate left: a pointer (*) or a type (char and many others, even ones that you've defined). If there's nothing on its left--that is, when it appears first--const applies to what's on its immediate right.
modified 15-Feb-21 7:23am.
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Hi Greg,
Thank you for your immediate response. I understood the point clearly.
Regarda,
Niharika
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Hi All,
I am learning callbacks in c.I found an example in callback but could not understand .Can some one please explain me how the flow of execution happens and brief explaination of program.
PFA code what I found.
<pre>* callback.c */
#include<stdio.h>
#include"reg_callback.h"
/* callback function definition goes here */
void my_callback(void)
{
printf("inside my_callback\n");
}
int main(void)
{
/* initialize function pointer to
my_callback */
callback ptr_my_callback=my_callback;
printf("This is a program demonstrating function callback\n");
/* register our callback function */
register_callback(ptr_my_callback);
printf("back inside main program\n");
return 0;
}
/* reg_callback.h */
typedef void (*callback)(void);
void register_callback(callback ptr_reg_callback);
/* reg_callback.c */
#include<stdio.h>
#include"reg_callback.h"
/* registration goes here */
void register_callback(callback ptr_reg_callback)
{
printf("inside register_callback\n");
/* calling our callback function my_callback */
(*ptr_reg_callback)();
}
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void my_callback(void)... /* This is the callback function that will be invoked. */
int main(void)
{
callback ptr_my_callback = my_callback; /* ptr_my_callback points to the function my_callback */
register_callback(ptr_my_callback); /* registers the callback */
}
/* This defines the type "callback". The '*' before "callback", which is in
parentheses, means that it's a pointer to a function. The function returns
void and takes (void) as its parameter. */
typedef void (*callback)(void);
/* This function is called to register the callback. It actually doesn't do
that, because registering would mean saving a pointer to it. All that it does
is invoke the function immediately, which is what it could do later if it
saved its parameter somewhere and used it to call the function when it was
time to do so. To call the function, it dereferences the pointer to it and
invokes it with no arguments. */
void register_callback(callback ptr_reg_callback)
{
(*ptr_reg_callback)();
}
The printfs are just there so that you can observe the flow of execution.
modified 10-Feb-21 11:52am.
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You might already be familiar with callbacks and not realize it. If you've ever used qsort() or bsearch(), or another library function that takes a function pointer as an argument to help it do its work, you have already used callbacks!
For example the signature for qsort is void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *)); and might be used like this struct foo {
char key[10];
int id;
};
int cmpfoo_bykey(const void *vp1, const void *vp2)
{
const struct foo *foo1 = vp1;
const struct foo *foo2 = vp2;
return strcmp(foo1->key, foo2->key);
}
int cmpfoo_byid(const void *vp1, const void *vp2)
{
const struct foo *foo1 = vp1;
const struct foo *foo2 = vp2;
return foo1->id - foo2->id;
}
int main()
{
struct foo my_data[100];
qsort(my_data, 100, sizeof(struct foo), cmpfoo_bykey);
qsort(my_data, 100, sizeof(struct foo), cmpfoo_byid);
return 0;
}
In the above example qsort() knows how to sort an array of items in a generic way, but not how to compare items. It gets around this limitation by using a callback function, that the programmer provides, that does know how to compare items in the array. So, whenever qsort() needs to know how two items in the array compare to each other, it calls back to the code provided by the programmer to determine how the two items compare to each other.
Keep Calm and Carry On
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I'm programming in C in an embedded environment and I have a bit-bang software UART I would like to be able to hook up to a myPrintf function, that supports the standard printf syntax, e.g.myPrintf("%s %3.2f\n", "Pi:", 3.14159);I would like to achieve this without having to use a big (=worst case length of "sentence" to transmit in a single myPrintf call) temporary buffer (otherwise, I could just go via sprintf). What I want to achieve is that my characters are sent over my UART "on the fly", so in the example above "Pi: " would be sent out over my UART before the float number has been converted to ASCII characters. Does anybody know how I can achieve this in the easiest way possible? Is the source code for printf available somewhere for public use so I can modify it to fit my needs?
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