In desktop publishing and word processing, the size of printed text is usually specified using a standard unit. Which of the following units is commonly used to measure font size in documents and on screen?

Introduction / Context:
This question tests your understanding of basic typography and how font size is specified in word processors and desktop publishing tools. When you choose a font size such as 10, 12, or 14 in a program like Microsoft Word, that number corresponds to a specific unit of measurement. Knowing the correct unit is important because it helps you control how large text appears on printed documents and on the screen. This is general computer knowledge that also connects to graphic design and publishing concepts.

Given Data / Assumptions:
The question states that font size is measured in some unit and asks which unit is used. The options are pixels, points, didos, and percents. We assume that the context is standard document preparation using common fonts like Times New Roman or Arial. We also assume that the question refers to the numeric font size shown in formatting toolbars, such as 12 for regular body text in many documents.

Concept / Approach:
In traditional typography, a point is a unit of measurement used to describe the size of characters. In many systems, one point is defined as one seventy second of an inch. When you select a 12 point font, you are using this typographic measurement. Pixels are units of screen resolution and vary with display density, so they are not the standard unit for fonts in document editors, although they are used in web and interface design. Percents are relative units used to scale objects, and didos are not commonly used in modern word processors. Therefore, the correct answer is points, which are specifically used as the standard unit for font size in most document based software.

Step-by-Step Solution:
Step 1: Recall that font size options in word processors are labeled as numbers like 10, 11, 12, 14, and so on.Step 2: Understand that these numbers refer to typographic points, a standard unit of measurement in printing.Step 3: Recognize that while pixels and percents are used in digital layout, they are not the primary unit used for traditional font sizing in documents.Step 4: Conclude that points are the correct unit used to measure font size.

Verification / Alternative check:
If you open any word processing software and check font settings, you will often see the label pt next to the font size drop down, indicating points. Documentation for desktop publishing programs also describes font sizes in points. Printing standards and typographic references further confirm that point sizes are used to define the height of characters in a consistent way across devices and printers. Although screen rendering may involve converting points to pixels, the user facing unit remains points.

Why Other Options Are Wrong:
Option A is wrong because pixels are primarily used to measure screen resolution and image dimensions, and they depend on screen density. Option C is wrong because didos are not commonly used in modern office software and are not a standard choice in font dialogs. Option D is wrong because percent values are used to describe relative scaling, not absolute font size. Option B, points used as a standard typographic unit, is the only option that correctly matches how font size is measured in typical document editing environments.

Common Pitfalls:
A common confusion arises when people see font sizes specified in CSS on web pages, where pixels and relative units are sometimes used. This can lead learners to assume that pixels must also be the primary unit for fonts in all contexts. Another pitfall is not noticing the pt label in software interfaces and assuming the number is unitless. Remember that traditional printing and many digital tools rely on points as a stable unit, even if the device internally converts those points to pixels for display.

Final Answer:
The correct answer is Points used as a standard typographic unit for font size.