In computer performance terminology, the speed of a personal computer CPU is commonly expressed in which unit that measures how many instructions it can execute per second?

Introduction / Context:
CPU speed is a critical measure of computer performance. It describes how quickly a processor can execute instructions. Over the years, different metrics have been used to express CPU performance. One traditional unit, especially in older computer awareness material, is MIPS, which stands for Millions of Instructions Per Second. Understanding this unit helps students interpret benchmark figures and exam questions about processor speed.

Given Data / Assumptions:

• The question asks how CPU speed of a personal computer is commonly expressed.
• Options include MIPS, KIPS, DPI, PPM and lumens per watt.
• We assume a context of instruction throughput, not printing or display quality.
• MIPS and KIPS are both instruction based units, while the others are unrelated.

Concept / Approach:
MIPS measures how many millions of machine level instructions a CPU can execute in one second. It is a rough indicator of performance. KIPS, or Thousands of Instructions Per Second, is a smaller scale measure that was more relevant for very early processors. DPI relates to printing and display resolution, PPM to printing speed and lumens per watt to lighting efficiency. For describing modern or classic personal computer CPU speeds in an exam context, MIPS is the standard answer.

Step-by-Step Solution:
Step 1: Recognise that CPU performance is often described in terms of how many instructions it can execute per unit time. Step 2: Millions of Instructions Per Second MIPS is a unit that expresses this throughput directly. Step 3: KIPS, Thousands of Instructions Per Second, is similar but at a much smaller scale, which was mainly used for older, slower computers. Step 4: Personal computers, especially from the time most basic computer books were written, were designed to achieve performance in the millions of instructions per second range, making MIPS a natural measurement. Step 5: DPI is a unit for resolution of printers and screens and has nothing to do with CPU instruction speed. Step 6: PPM measures how many pages a printer can output per minute, again unrelated to CPU instruction execution. Step 7: Lumens per watt is a measure of lighting efficiency and is not used in computer performance at all. Step 8: Therefore, the most appropriate unit among the options is Millions of Instructions Per Second MIPS.

Verification / Alternative check:
Older computer architecture and operating systems textbooks often provide examples where CPU speeds are given in MIPS. Although modern performance comparisons now use different metrics such as clock speed in gigahertz and benchmark scores, exam oriented questions still ask about MIPS as a classic unit. These same sources rarely use KIPS for personal computers, reserving it for much older or simpler processors, which supports choosing MIPS for a personal computer CPU.

Why Other Options Are Wrong:
KIPS is technically a valid unit for instruction throughput but does not match the scale at which personal computer processors are normally described in educational material. DPI and PPM belong entirely to the domain of printing or display devices, not processors. Lumens per watt is used in lighting engineering to describe how efficiently a light source converts electricity into light. None of these alternatives is a standard CPU performance unit for personal computers.

Common Pitfalls:
Students sometimes mix up different performance metrics because they encounter many acronyms at once. To avoid confusion, link MIPS specifically with CPU speed, DPI with image clarity, PPM with printer output and lumens per watt with lighting. Visualising each unit in its real world context can make it easier to remember the correct associations during exams.

Final Answer:
The CPU speed of a personal computer is commonly expressed in Millions of Instructions Per Second MIPS.