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4. Terminology

4.1 Data Size

Even though the F-CPU word size is 64 bits, we prefer to stick to H&Ps and standard RISC notation. Since this is a matter of convention, we believe keeping with tradition is more befitting to this case.

4.2 Exceptions

The word exception is used to designate traps, interrupts, faults and exceptions. Exceptions can be divided in various classes, as described by H&P.

4.3 Context switch vs. Process switch

Many authors do not make a distinction between the expressions context switch and process switch (e.g. Tanenbaum or H&P). However, in this document we shall use the definitions found in [Stallings, William, Operating Systems, Macmillan 1992, p. 148]. Quoting:

It is clear, then, that a context switch is a concept distinct from that of a process switch. A context switch may occur without changing the state of the process that is currently in the Running state. In that case, the context saving and subsequent restoral involve little overhead. However, if the currently running process is to be moved to another state (Ready, Blocked, etc.), then the operating system [the kernel] must make substantial changes in the environment.
...
Thus, the process switch, which involves a state change, requires considerably more effort than a context switch.

4.4 Jumps and Branches

Again, well stick to H&P terminology: jump will be used when the PC is changed unconditionally and branch will be used when it is changed conditionally.


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