Understanding External Memory vs. Other Devices

The question asks to identify which among the given options is NOT an external memory. Let's first understand what external memory is in the context of computers and then look at each option.

External memory refers to storage devices that are not part of the main computer system's internal memory (like RAM). These devices are typically used for long-term storage of data and can often be removed from the computer. They provide additional storage space and allow for data portability.

Analyzing the Options

• DVD (Digital Versatile Disc): A DVD is an optical storage medium. DVDs are used to store movies, software, and data. They are external storage devices because they are separate discs inserted into a computer's DVD drive for reading or writing data.
• Pen drive: A pen drive (also known as a USB flash drive) is a portable flash memory device. It plugs into a USB port on a computer and is used for storing and transferring data. Pen drives are classic examples of external memory devices due to their portability and use for data storage outside the main system.
• Scanner: A scanner is a device that optically reads images, printed text, or handwriting and converts it into a digital image. It is an input device. Its primary function is to get data into the computer system, not to store data long-term like memory devices do.
• Hard Disk: A hard disk drive (HDD) is a data storage device used for storing and retrieving digital information using rapidly rotating disks coated with magnetic material. While some hard disks are internal to the computer, external hard disks are also very common. These connect via USB or other interfaces and are used for backup and additional storage, making them a type of external memory device.

Identifying the Non-External Memory Device

Based on the analysis:

• DVD is an external storage device.
• Pen drive is an external storage device.
• Hard Disk (specifically external type, but even internal is related to long-term storage as opposed to an input device) is a storage device.
• Scanner is an input device, not a storage device or memory.

Therefore, the Scanner is the only option that does not function as an external memory device; it is an input device.

Conclusion

The device among the options provided that is NOT an external memory is the Scanner.