C / C++ / MFC

DWORD dwWritten;
BOOL result = WriteFile(hFile, &st, sizeof st, &dwWritten, NULL);

#include	<windows.h>
#include	<conio.h>
#include	<iostream>

using namespace std;

struct Detail{
	wchar_t Name[25];
	long	Age;
	wchar_t Address[100];
};

struct Student{
	Detail detail;
	DWORD code;
};
 
int main()
{

	DWORD BytesWritten=0, BytesRead=0;
	Student st,read;

	st.code =1;
	st.detail.Name = TEXT("Williams");
	st.detail.Age = 25;
	st.detail.Address = TEXT("B-33 Lane 5");
	
	
	HANDLE hFile = CreateFile(TEXT("C:\\demo.txt"),GENERIC_READ | GENERIC_WRITE,0,0,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,0);
	if (hFile != INVALID_HANDLE_VALUE)
	{
		WriteFile(hFile,&st,sizeof(Student),&BytesWritten,0);
		ReadFile(hFile,&read,sizeof(Student),&BytesRead,0);
		CloseHandle(hFile);

		cout<<read.code<<endl;
		cout<<read.detail.Name; 
	}
	else
	{
		cout<<"Error! Cannot Open File";
		exit(1);
	}
	_getche();
	return (0);
}

Error	1	error C2440: '=' : cannot convert from 'const wchar_t [9]' to 'wchar_t [25]'
Error	2	error C2440: '=' : cannot convert from 'const wchar_t [12]' to 'wchar_t [100]'	

goldenrose9 wrote:

st.detail.Name = TEXT("Williams");
st.detail.Address = TEXT("B-33 Lane 5");

DavidCrow wrote:

You probably meant to use _tcscpy() here instead.

_tcscpy(st.detail.Name,TEXT("Williams"));
_tcscpy(st.detail.Address,TEXT("B-33 Lane 5"));

struct Detail{
	wchar_t Name[25];         
	long	Age;              
	wchar_t Address[100];
};

struct Student{
	Detail detail;
	DWORD code;
};

Student st;
st.code = 1;

_tcscpy_s(st.detail.Name,_tcslen(st.detail.Name),TEXT("WILLIAMS"));

goldenrose9 wrote:

why error is occurring in _tcscpy_s()

Student st,read;
ZeroMemory(&st,sizeof(st));

goldenrose9 wrote:

i was making a small mistake.

_tcscpy_s(st.detail.Name,sizeof(st.detail.Name),TEXT("WILLIAMS"));

st.code =1;
st.detail.Age = 25; 

st.code = 4278124286
st.detail.Age = -16843010

st.code =1;
st.detail.Age = 25;
_tcscpy_s(st.detail.Name,sizeof(st.detail.Name),TEXT("WILLIAMS"));
_tcscpy_s(st.detail.Address,sizeof(st.detail.Address),TEXT("BB-33 LANE 5"));

st.code = 1;
st.st.Age = 25;
_tcscpy_s(st.st.Name, sizeof(st.st.Name), TEXT("WILLIAMS"));
_tcscpy_s(st.st.Address, sizeof(st.st.Address), TEXT("BB-33 LANE 5"));

st.code = 4278124286
st.detail.Age = -16843010

st.code = 1;
st.st.Age = 25;
_tcscpy_s(st.st.Name, sizeof(st.st.Name), TEXT("WILLIAMS"));
_tcscpy_s(st.st.Address, sizeof(st.st.Address), TEXT("BB-33 LANE 5"));

Error	1	error C2039: 'st' : is not a member of 'Student'	
Error	2	error C2228: left of '.Age' must have class/struct/union

goldenrose9 wrote:

when executing this code following error occurs.

Student
    st = {{TEXT("Williams"), 25, TEXT("B-33 Lane 5")}, 1 },
    read = {0};

WriteFile(hFile,&st,sizeof(Student),&BytesWritten,0);
SetFilePointer(hFile, 0, 0, FILE_BEGIN);
ReadFile(hFile,&read,sizeof(Student),&BytesRead,0);

st.detail.Name = TEXT("Williams");

jk chan wrote:

you can use fopen("file","wb"); and fwrite C run time APIS.

is it so complicated?

manchukuo wrote:

but the 2nd solution you post how could it be implemented?