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Unformatted text preview: termination.
2. Process can intercept the signal and ignore it.
3. Process can intercept the signal and take a programmer-defined action.
We will discuss signals in detail in some of the subsequent lectures. Hardware Protection
Multi-programming put several programs in memory at the same time; while this
increased system utilizatio n it also increased problems. With sharing, many processes 4 could be adversely affected by a bug in one program. One erroneous program could also
modify the program or data of another program or even the resident part of the operating
system. A file may overwrite anothe r file or folder on disk. A process may get the CPU
and never relinquish it. So the issues of hardware protection are: I/O protection, memory
protection, and CPU protection. We will discuss them one by one, but first we talk about
the dual- mode operation of a CPU.
a) Dual Mode Operation
To ensure proper operation, we must protect the operating system and all other programs
and their data from any malfunctioning program. Protection is needed for any shared
resources. Instruction set of a modern CPU has two kinds of instructions, privileged
instructions and non-privileged instructions. Privileged instructions can be used to
perform hardware operations that a normal user process should not be able to perform,
such as communicating with I/...
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- Spring '12