The grep is general system software. A homework score average program is application software. The ls program is OS software. The fprintf function is general system software. A spreadsheet program is application software.
Abstract resources are virtual resources implemented the low-level system software.
These resources provide important services but have no direct physical realization. Examples of abstract resources include, Ram Disks and Virtual Memory. This is ideal for data processing and number crunching applications. Time sharing is perferred when the system is used for interactive processes. This ideal for application development, text processing, and other user centered uses of today's computers.