Are the programs written on schedulers ,thread library , process management, memory management, et al called systems programs ? How are they different from the programs that implement functions like open() , printf() , scanf() , read() .. they have a prefix sys_open, sys_close, sys_read etc , right ? Is there any difference of hierarchy between the programs that implement system calls and system level programs like that implement thread library, process management , memory managemnt etc..

Hope you understood my qstn

Actually, those are functions, not programs. They interact with the OS through system calls (to system functions). Does that help?

are the programs that implement the library functions system level programs ?

i smell home work.

There are no programs that implement the library functions. This may seem like a fine distinction, but it must be made, nonetheless. A program is a self-contained unit having a "main()" function. Note the word "function". Programs are made of code and calls to functions, not the reverse. Functions are self-contained bits of code that may call other functions. They do not contain a "main()" function. You really need to discuss with your instructor the difference between a function and a program.

I got this cleared ..Here goes the clarification
" Functions like open() , printf() , scanf() , read() are library function implemented on top of their sys_* counterparts so they can be used for any Application development. On the other hand sys_open, sys_close, sys_read etc are implemented as-part-of-system commonly known as kernel. On top of this, system programs like thread library, compilers, linkers are implemented which helps other application development. Hope this clears the difference between system, system programs and application programs. "