Question

Please provide the required libraries,structures and data fields needed to open and read files.

These files are made in C programming language on ubantu running linux OS.

Answer 1

1.Required Header files are
stdio.h is used to call the built-in function(fopen,fclose
stdlib.h
example
#include <stdio.h>
#include <stdlib.h>
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2. FILE(available in stdio.h) type pointer
Example FILE *fp;
you need a pointer which can point your file.
it means that with help of this pointer you can track your
file, this pointer allows you to manage your file such as opening,
reading, and writing data to/and from a file.
FILE is a structure data type(built-in):
it holds information of file such as size of file and so on.
3. NULL(it is a macro available in both stdio.h and stdlib.h) and fopen(built in function, it is used to open the file.)
fopen() returns FILE pointer if file is open successfully
otherwise it will return NULL pointer, it means file could not be open.
NULL pointer means no valid memory address assigned.
Example:-
FILE *fp;
fp = fopen(filename, "r");//"r" means read mode
if (fp == NULL)
{
printf("Cannot open file \n");
exit(0);
}
4. EOF(macro available in stdio.h)
it is used to detect the end of file character.
so you should read file till the end.
there is EOF character at the end of file.
and should stop the reading if reached at the end of file.

5. fclose(built in function, it is used to close the file.)
Example:-
ch = fgetc(fp);
while (ch != EOF)
{
printf ("%c", ch);
ch = fgetc(fp);
}
difference between macro and function
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when function is called, control goes to the body of the function.
after the execution of body control returns back to the normal sequence
so, it time consuming process(to send control some where else)

when macro is used a copy is inserted in the program's memory
so there is no need to send control anywhere.
that's why macro is faster than function.

but macro consumes more memory(due to it's insertion in program's memory) in comparison of function.
function takes less memory.

you can put all the above things together to make a useful program.