System Kernel -
The kernel is the heart of the UNIX. When the system is booted, the kernel forms an interface between the hardware and the shell. All the other components like programs and commands call on the kernel's services. The kernel, in turn consults its data tables as it schedules users' programs, allocates resources to the Program, and manages the low-level exchange of data with the computer's hardware. For example, if a program requests file service to the kernel, it gives a system call. The kernel then checks the disk drive to get data from the file and transfers it to the buffer. Finally, The program collects the data. The kernel contains a changeable set of device drivers to accommodate variations in hardware.
The UNIX system kernel provides the following functions -
1. File management and security
2. Memory management
3. Process scheduling and management
4. Input/Output services
5. System accounting
6. Interrupt and error handling
7. Date and Time services.