Can anybode suggest me where to find the source code for system calls itself? Like open(), read(), close(). May I have the link or book where I can find the source code these functions itself?
When ever we quit a file or save and quit a file, the file content is stored in the disk. Internally, after putting the contents on the disk the kernal calls close() system call to close/quit the file. Am I right with what I said? please tell the alternative answer for what is happening inside on closing/quitting a file, if mine is wrong?
Download the libc source code of the appropriate system. You'll find libc sources for Linux, bsd and Solaris on the net.
Give some context. Quit and save aren't system calls either. Do you mean typical commands from the file menu? No. The application calls close(). The OS itsself takes care about writing the actual data to disk. Typically it won't write the contents to disk immediately but just send them to some buffer which is cleaned whenever the disk comes idle or the filesystem is unmounted.
System calls, by definition, are part of the operating system. If the source code for your operatnig system is available, you can download and browse it. Similarly for the C library, you can download the source for e.g. GNU glibc.