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System Software
Notes
Figure 2.14: Different Stages of Program Execution
2.5.2 I/O Operations
Each program requires an input and produces output. This involves the use of I/O. The operating
systems hides from the user the details of the underlying hardware for the I/O. What the user
sees is that the I/O has been performed without any details.
For efficiency and protection, the users cannot control I/O, so this service cannot be provided by
user-level programs.
Figure 2.15: I/O Operation Handling
42 LOVELY PROFESSIONAL UNIVERSITY
