"Everything is a file".
 

When we say that everything is a file in linux what does it basically means,because in windows also we can find a file for everything eg for printer or any device or any log.
Thanks.

It means that devices live in /dev, memory can be directly access under /proc etc., whereas a windows printer is NOT a file. you can't literally write text to a printer file in windows and see it come out on paper. You really can do this on Linux (echo "THIS IS A TEST" > /dev/lp0) etc. A simpler example is a disk, you can open up /dev/sda1 in a text editor if you so desire and see the raw contents of a disk.

Note though that whilst it's nice to say so, LOADS of things actually aren't files. Like sound and network interfaces in most cases these days (I think)

If lets say printer is not a file in windows then how come other programs able to use it?,what do they actually uses to have access on printer?
i.e if I want to use a printer in my program I will have to access printer's device driver.

*you* don't use the driver, there's no actual file that IS the printer. It disappears into hardware abstraction code and gets dealt with like that. I don't know all that much about how it works, but the basic point here is there is no c:\windows\systems32\davesprinter.prn or something similar.

Actually, there are shitty remnants of this is the DOS environment I believe. On unix you can run "echo TEST > /dev/ttyS0" which would write the word "TEST" to the first serial port, there IS a file at /dev/ttyS0. On windows the same would be "type TEST > COM1" But note here that COM1 is NOT a file. It was just a nasty nasty hack where using the word "COM1" would be arbitrarily pulled out of the ether and sent into the 1st serial port, rather than a file called "COM1"

You neither access a "printer file" nor the driver directly, you use functions of one of Windows' APIs to print something: http://msdn.microsoft.com/en-us/libr...(v=vs.85).aspx