In optical storage technology, which of the following statements correctly describes a standard CD-ROM disc?

Introduction / Context:
This question explores basic properties of optical storage media, specifically CD-ROM discs. Understanding the differences between CD-ROM, CD-R and CD-RW is important for both historical and practical reasons. Although optical media are less common today, many computer awareness syllabi still include questions about their characteristics, such as whether they can be rewritten and how their storage capacity compares to floppy disks.

Given Data / Assumptions:

• The question asks which statement correctly describes a CD-ROM disc.
• Options discuss erasability, comparison with CD-R, data capacity versus floppy disks and type of recording technology.
• We assume a standard pressed CD-ROM produced at a factory, not recordable or rewritable variants.

Concept / Approach:
CD-ROM stands for Compact Disc Read Only Memory. Data on a CD-ROM is stamped or pressed during manufacturing and cannot be changed by the user. Users can read the data multiple times but cannot erase or rewrite it. CD-R discs are recordable once by the user, and CD-RW discs are rewritable. CD-ROMs typically store around 650 to 700 megabytes of data, which is far more than a traditional floppy disk that holds about 1.44 megabytes. CD-ROMs are optical, not magnetic, media.

Step-by-Step Solution:
Step 1: Recognise that the term Read Only in CD-ROM indicates that users cannot modify the data once it is created. Step 2: Option a states that a CD-ROM disc cannot be erased and rewritten once manufactured, which matches the definition of Read Only Memory. Step 3: Option b claims that a CD-ROM has more capacity than a CD-R. In reality, standard capacities of CD-ROM and CD-R are similar; both store around 650 to 700 megabytes. So this statement is misleading. Step 4: Option c states that a CD-ROM holds less data than a floppy disk, which is false, because CD-ROMs hold hundreds of megabytes while floppy disks hold roughly 1.44 megabytes. Step 5: Option d combines write once and erase, which describes neither CD-ROM nor CD-R correctly. CD-R can be written once but not erased or rewritten. Step 6: Option e incorrectly states that CD-ROMs are designed mainly for magnetic recording, while they actually use optical laser based technology. Step 7: Therefore, the only correct statement is option a.

Verification / Alternative check:
Technical references on optical storage describe CD-ROM as a pressed disc format where the data is physically formed into the disc surface during manufacturing. Consumer drives can read the reflected laser pattern but cannot alter it. The same resources compare storage capacities, showing that CD-ROMs store hundreds of megabytes, far exceeding floppy disk capacity. They also explain that CD-ROMs use optical recording, not magnetic, confirming that options c and e are incorrect.

Why Other Options Are Wrong:
Option b incorrectly suggests a difference in capacity between CD-ROM and CD-R; capacities are broadly similar for standard discs. Option c reverses the relative sizes of CD-ROM and floppy disks. Option d mistakenly suggests that a CD-ROM can be written once and then erased, which is actually a misdescription even for CD-R discs. Option e confuses optical and magnetic technologies. Only option a correctly describes the read only nature of CD-ROM discs.

Common Pitfalls:
Students sometimes confuse CD-ROM with CD-R and CD-RW because all use similar looking discs. To avoid this, remember the acronyms: ROM for Read Only Memory, R for Recordable once and RW for ReWritable. Linking these abbreviations to their meanings will help you quickly determine which discs can be written, rewritten or only read, and answer such exam questions confidently.

Final Answer:
A standard CD-ROM disc is correctly described by the statement that it cannot be erased and rewritten once manufactured.