Operating system linux/unix consist of kernel, System program and Several application program. Kernel be kernel from operating system that regulate memory use, Product input apparatus, Processes, File use in file system and Others. Kernel also prepare service nest that used to accessing kernel that called system call. System call this used to introduce various service that wanted by operating system.
System program and All anothers programs that walk above kernel called fashion user. Difference between system program and Application program system program be wanted so that a operating system ambulatory while application program program that is want to run a certain application. Example: Daemon be system program and Word processing (word processor) be application program.