Question

2. The binary file dates.bin is shown in a hexadecimal editor: DXV132 - dates.bin File Edit earch Address Bookmarks Tools VIscript Help 7000000303530|353134 30333233 31 33 0 5 0 5 1 4 0 323 1 3 ▲ 10 30 31 32 35 31 34 30 38 31 36 31 32 30 37 33 3101 2 5 1 4 0 8 1 6 1 20731 20 31 34 30 32 30 36 31 32 31 31 32 33 31 35 30 39 1 4 0 2 0 61 2 11 2 3 1509 30 31 34 31 33 1 4 1 3 Delete Adr. hex: 0 Char dec: 7 Overwrite The file is full of dates. It starts with an integer (4 bytes) giving the number of dates. The dates are formatted as MMDDYY (two chars for the month, two chars for the day, and two chars for the year). Write a program that reads in this file (or any similarly formatted version of it) and stores all dates from 2014 into a new file called newdates.bin. The new file is a binary file with the same format as dates.bin .

Is any one can help me to write the code? Please.

Answer 1

struct is analogous to a class. there are differences but you can ignore for now.

here we have created a struct named date which has 3 arrays namely m,d,y each of size 2 and typr char.

we can create object of struct date.eg

strcut date todaysdate;

the arrays can be accessed as follows

todaysdate.m[0]

. FILE pointer to create and use FILE for different operations.

syntax

FILE* filePointerName;

eg.File*infile

fopen()

syntax

fopen(“fileName”,”mode”);

eg.

file*infile=fopen("dates.bin",rb)

rb=readmode for non text files

wb=write mode for non text files

fread()

It is used to read data from file.

syntax of the function is:

fread (void* ptr, t size, t count,FILE* stream)

Parameters

ptr: pointer to memory where the read data will be stored.
size: size of data elements (in byte) to be read.
count: number of data elements to be read.
stream: pointer to the file from which the data will be read.

Return

Type: t
Value: On success number of elements which are successfully read.
On failure returns zero (0) if the size or count is 0, Error indicator is set.

eg.in our case

fread returns the first integer and since as stated the first integer=number of dates in infile hence datecount.

then we create arrays namely dates and keeperdate both of size datecount

fread(dates,sizeof(struct date),datecount,infile)

reads all dates and stores it in array dates as objects of struct date

Note: fread skips those characters which do not obey the size specified , so second call to fread does not reads the datecount which is the first integer in your file.

the for loop.

iterates through dates array and

It checks if the year of date ==14 [since we have to only copy dates of 2014]

if(yes)

save that date in Keeper array and increment keepercount

fwrite().

It is used for file writing.

syntax is:

fwrite(const void* ptr, t size,t count,FILE* stream)

Parameters:

ptr: pointer to the data which will be written.
size: the size of data elements (in byte) to be written.
count: number of data elements to be written.
stream: the pointer to the file where the data will be written.

Return

Type: t
Value: On success number of elements which are successfully written
On failure zero (0) if the size or count is 0. Error indicator is set.

fwrite(&keppercount,sizeof(int)1,outfile);

it simply outputs datecount as first integer of file

fwrite(keeperdates,sizeof(struct date),keepcount,outfile)

outputs all date objects in keeperdates array into outfile.

return 0; to exit

Note: fwrite appends to end of file.