Computer Memory and Storage

Here, memory systems have long used parity bits for error detection and correction.

It is the P+Q redundancy schemes, stores extra redundant information to guard against multiple disk failures.

It is a directory, file system or automatic storage management disk group that serves as the default storage area for files related to recovery.

Disk controllers can detect whether a sector has been read correctly, so the single parity bit can be used for error correction as well as for detection.

It keeps a parity block on a separate disk for corresponding blocks from N other disks.

PROM stands for Programmable Read Only Memory, a type of non-volatile memory that can be programmed once after manufacture. Unlike ROM which is programmed during fabrication, PROM comes blank from the factory and can be written to once using specialized programming equipment. After programming, the data cannot be modified.

Magnetic tape provides the highest storage capacity (often terabytes) among storage media but has the slowest access time due to sequential access requiring physical tape movement. This creates a fundamental trade-off in storage hierarchy: tape maximizes capacity and minimizes cost per GB, while cache and RAM prioritize speed over capacity. The storage pyramid places tape at the bottom for bulk archival.

DRAM (Dynamic RAM) stores each bit in a capacitor that holds an electric charge. Since capacitors gradually leak charge, DRAM requires periodic refreshing to rewrite the data and prevent information loss. SRAM uses flip-flops and doesn't need refreshing, while ROM and PROM are non-volatile memory types that retain data without power and don't require refreshing.

A block is a fixed-size unit of data storage and retrieval, typically consisting of multiple bytes or items handled as a single entity. Files are stored as sequences of blocks on disk, and read/write operations often transfer entire blocks for efficiency rather than individual items. Block sizes vary by system but are commonly 512 bytes, 1KB, or 4KB.

Magnetic tape offers the lowest cost per gigabyte for backup storage, making it economical for archiving large datasets. While optical media have low per-disc costs, their limited capacity (700MB for CD, 4.7GB for DVD) makes them more expensive per GB for substantial backups. RAID systems provide fast access but significantly higher cost per unit of storage.

Back-up is correct because it specifically refers to creating a duplicate copy for data protection. Ethical use and proper disk storage are concepts, not backup copies. Scrolling is viewing different parts of a document.

The clipboard is a temporary storage area in memory that holds data cut or copied from one location so it can be pasted elsewhere. The immediate window is for debugging code, work area is not standard terminology, and a dialog box is a UI element for user interaction - none are temporary storage like the clipboard.

Floppy disks use magnetic read/write heads that physically contact the disk surface to read and write data, similar to hard drives. CDROM and DVDROM are optical media that use laser beams, not magnetic heads. A read/write head is characteristic of magnetic storage technology.