MGMT 1030 Lecture Notes - Lecture 15: Instruction Set
6 May 2018
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MGMT 1030 Lecture 15 Notes – Operations
Introduction
• The operation may be a move or load, it may be an addition or subtraction, it may be an
input or output, or it may be one of many other operations that we have already
discussed.
• Actually, if you think about the classes of instructions that we have discussed, you will
realize that there are only a very few instructions that do not operate on data.
• Some of these are concerned with the flow of the program itself, such as unconditional
JUMP instructions.
• There are also instructions that control the administration of the computer itself
• The only example in the Little Man Computer instruction set is the COFFEE BREAK or
HALT that causes the computer to cease executing instructions.
• Another example on many computers is the NO OPERATION instruction that does
nothing but waste time
• Which can be useful when a programmer wants to create a time delay for some reason
• Most modern computers also provide instructions that aid the operating system
software in its work, by providing security, controlling memory access, and performing
other functions.
• Because the operating system will frequently be controlling many tasks and users, these
istrutios ust ot e availale to the users’ appliatio programs.
• Only the operating system can execute these instructions.
• These instructions are known as privileged instructions.
• The HALT instruction is usually a privileged instruction, because you would not want an
individual user to stop the computer while other users are still in the middle of their
tasks.
• Computer manufacturers usually group the instruction set into various categories of
instructions
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