Page 550 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

At first blush, the terms multitasking, multicore,

multiprocessing, multiprogramming, and multithreading may
seem nearly identical. However, they describe very different ways
of approaching the “doing two things at once” problem. We

strongly advise that you take the time to review the distinctions
between these terms until you feel comfortable with them.

Multitasking In computing, multitasking means handling two or
more tasks simultaneously. In the past, most systems did not truly
multitask because they relied on the operating system to simulate
multitasking by carefully structuring the sequence of commands sent
to the CPU for execution. When a processor was humming along at
multiple gigahertz, it was hard to tell that it was switching between

tasks rather than working on two tasks at once. A single-core
multitasking system is able to juggle more than one task or process at
any given time.

Multicore Today, most CPUs are multicore. This means that what
was previously a single CPU or microprocessor chip is now a chip
containing two, four, eight, or potentially dozens of independent
execution cores that can operate simultaneously.

Multiprocessing In a multiprocessing environment, a

multiprocessor computing system (that is, one with more than one
CPU) harnesses the power of more than one processor to complete the
execution of a multithreaded application. For example, a database
server might run on a system that contains four, six, or more
processors. If the database application receives a number of separate
queries simultaneously, it might send each query to a separate

processor for execution.

Two types of multiprocessing are most common in modern systems
with multiple CPUs. The scenario just described, where a single
computer contains multiple processors that are treated equally and
controlled by a single operating system, is called symmetric
multiprocessing (SMP). In SMP, processors share not only a common

operating system but also a common data bus and memory resources.