Question

Storage capacity of CD is .....

• A. 600MB
• B. 1000MB
• C. 700 MB
• D. None of these

Hint:

Remember standard optical disc capacities for competitive exams: CD = 700 MB, standard single-layer DVD = 4.7 GB, and standard single-layer Blu-ray = 25 GB.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The topic here is Computer Hardware and Storage Media. The question asks for the standard storage capacity of a Compact Disc (CD). This requires knowledge of historical and technical standards established by the "Orange Book" and "Red Book" specifications that govern how data is physically and logically stored on optical media. Understanding these capacities is vital for understanding the evolution of data storage from magnetic to optical formats.
Step 2: Key Formulas and approach:
The approach is based on identifying industry standard specifications for optical media. There are no formulas to calculate this from scratch, as it is a manufactured specification. However, one can recall the relationship between time and data:
1. Standard Audio CD = 80 minutes of audio.
2. Data capacity conversion = Approximately 700 MB.
We compare the provided options against the globally accepted manufacturing standard for a standard-sized (120mm) CD.
Step 3: Detailed Explanation:

Historically, the first CDs (Compact Discs) had a capacity of about 650 MB, which corresponded to 74 minutes of audio.

As manufacturing processes improved, the industry standard shifted to the 80-minute disc, which provides a storage capacity of 700 MB.

700 MB is the most common and universally recognized capacity for a standard CD-R (Recordable) or CD-ROM used for software and data backup.

In contrast, 600 MB is an irregular size, and 1000 MB (1 GB) exceeds the physical data density limits of the standard CD laser technology (which uses a 780nm infrared laser).

Therefore, in any standard computer science context, 700 MB is the definitive answer for the storage limit of a typical CD.

Step 4: Final Answer:
The standard storage capacity of a CD is 700 MB.

Answer 2

Instead of simply citing the standard, we can arrive at the CD's data capacity by working through the numbers behind its audio format directly.

A standard audio CD, as defined by the Red Book specification, stores uncompressed stereo audio sampled at \( 44{,}100 \) samples per second, with \( 16 \) bits per sample, across \( 2 \) channels. The data rate this produces is:

\[ 44{,}100 \times 16 \times 2 = 1{,}411{,}200 \text{ bits per second} \]

Converting to bytes per second:

\[ \frac{1{,}411{,}200}{8} = 176{,}400 \text{ bytes per second} \]

A standard disc holds about \( 80 \) minutes of audio, which is \( 80 \times 60 = 4800 \) seconds. Multiplying the data rate by the playing time gives the total data capacity:

\[ 176{,}400 \times 4800 \approx 846{,}720{,}000 \text{ bytes} \]

Converting this to megabytes (using \( 1 \text{ MB} = 1{,}048{,}576 \text{ bytes} \)):

\[ \frac{846{,}720{,}000}{1{,}048{,}576} \approx 807 \text{ MB} \]

This raw audio-derived figure is close to but a bit higher than the commonly quoted 700 MB, because the widely advertised 700 MB rating is the usable data capacity after accounting for the disc's additional error-correction and formatting overhead, which is not present in this simple raw audio-bitstream calculation. Once that overhead is factored in, the practical, universally quoted capacity of a standard CD comes out to 700 MB.

Therefore, the correct answer is 700 MB.