The total size would be 5.
Since 'int a' takes 2; 
'char b' takes 1; and
'int *p' takes 2 (Note: Any pointer variable would take 2 bytes)

There is no additional size of 'struct' data structure.
Hence 5 is the value.

void main()
{
int x,y;
y=&abc.a;
x=(&abc->p+1);
printf("%d",x-y);
}

11

system calls are provided by the system and are executed in
the system kernel. They are entry points into the kernel and
are therefore NOT linked into your program. These are not
portable calls.
·   Library calls include the ANSI C standard library and
are therefore portable. These functions are linked into your
program.
It is worth noting that, because system calls are part of
the O/S. The program has to make a context switch to the
kernel when they are called and because of this, they have a
high startup overhead. The upside is that the time executing
these routines is assigned to the OS and not the user program.

union elements share common memory space

Embedded software is a program which will interact with the 
physical world. This will be written for a perticular 
machine or device which will be dedicated to that for ever.
example: Embedded software is buil in to electronic systems 
or cars, home appliances, televisions etc

Normal Software is nothing but the information technoly.

open() is the function created by the user......... which can be used to perform a specific task....

fopen() belongs to FILES..... this is a in built user defined function which is used to open a file which is already existing with the opening mode or create a new file....and which returns a pointer 

syntax:
   file_ptr=fopen("file name","opening mode");

writing program for database management like emplyoee
records....

arraging element in proper order

1.changing d sizeof cursor,
2 clearing d content of screen,
3 drawing graphics shapes 
4 formatting floppy drive
5 interacting with mouse