Mapping only first letter of file C - c

Question

how can I map only the first letter of my file??
I've tried these value for parameters :
1, // maximum object size (high-order DWORD)
1, // maximum object size (low-order DWORD)
(i don't know the difference between them).
is 1 the right parameter for an only 1 letter mapping?
#define FILENAME "c:\gibrish.bin"
#include <Windows.h>
#include <stdio.h>
int main()
{
HANDLE hFile;
LPCSTR pFileName = FILENAME;
hFile = CreateFileA(pFileName, // file name
FILE_MAP_ALL_ACCESS, // access type
0, // other processes can't share
NULL, // security
OPEN_EXISTING, // open only if file exists
FILE_ATTRIBUTE_NORMAL, NULL);
HANDLE hMapFile;
////////mapping here
hMapFile = CreateFileMappingA(hFile, // file handle
NULL, // default security
FILE_MAP_ALL_ACCESS, // read access
1, // maximum object size (high-order DWORD)
1, // maximum object size (low-order DWORD)
// 0 means map the whole file
"gibrishFile"); // name of mapping object, in case we
// want to share it
return 0;
}

Answer 1

how can I map only the first letter of my file??
I've tried these value for parameters :
1, // maximum object size (high-order DWORD)
1, // maximum object size (low-order DWORD)
these two parameters makes (a huge) number, if the number you want to give is 1 or any other under 2^32 the high-order DWORD must be 0. If you give 1 and 1 this means the number is 1*(2^32) + 1 = 4294967296, this is not compatible with only the first letter
From https://learn.microsoft.com/en-us/windows/desktop/winprog/windows-data-types :
DWORD A 32-bit unsigned integer. The range is 0 through 4294967295 decimal.

Answer 2

There is no parameters FILE_MAP_ALL_ACCESS in CreateFileMappingA msdn doc. The return value will always be failed, with GetLastError() return 87(ERROR_INVALID_PARAMETER). And the folder you are accessing is the "C:\\", If you don't have enough authority, CreateFileA will return a INVALID_HANDLE_VALUE and get error of 5(ERROR_ACCESS_DENIED).
CreateFileMappingA is used for creating space for mapping, but not the actual size you want to map. And then use MapViewOfFile() mapping into the address space of a calling process. And the size you want to map must <= the size you create.