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Question 16 of 22 · Abbreviations & Full Forms
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SSC

In computing, what does 'DASD' stand for?

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Answer: Option A — Direct Access Storage Device

Detailed Solution

In computing, DASD (pronounced "daz-dee") stands for "Direct Access Storage Device".

About DASD:

  • It is a secondary storage device in which each physical record has a distinct location and a unique address, so that data can be read or written directly (randomly) without reading through all the preceding data.
  • The term was introduced by IBM in the 1960s, especially for its mainframe computers (such as the IBM System/360).

Examples of DASDs:

  • Hard disk drives (HDDs): the most common DASD.
  • Floppy disks and optical discs (CDs, DVDs).
  • Solid-state drives (SSDs) and flash drives.
  • Earlier, magnetic drums.

DASD vs. sequential access:

In a "sequential access storage device" (SASD), data must be read in order, from the beginning, to reach a particular record. The best example is magnetic tape.

In a DASD, any data can be reached directly by its address, which is much faster for random access.

This is similar to the difference between a music cassette tape (sequential) and a CD (direct access).

History:

IBM introduced the first commercial hard disk drive, the "IBM 350 Disk Storage Unit", in 1956, as part of the IBM 305 RAMAC (Random Access Method of Accounting and Control) computer. It stored about 5 megabytes on fifty 24-inch disks and weighed about a tonne.

Related computer storage terms:

  • RAM: Random Access Memory (primary, volatile memory).
  • ROM: Read-Only Memory (non-volatile).
  • HDD: Hard Disk Drive.
  • SSD: Solid-State Drive.
  • RAID: Redundant Array of Independent (or Inexpensive) Disks.
  • SAN: Storage Area Network.
  • NAS: Network-Attached Storage.

Storage units:

1 byte = 8 bits; 1 kilobyte (KB) = 1,024 bytes; 1 megabyte (MB) = 1,024 KB; 1 gigabyte (GB) = 1,024 MB; 1 terabyte (TB) = 1,024 GB.

Why not the other options?

  • ✗"Digital Audio Storage Disk" is not the correct expansion.
  • ✗"Data Access Security Device" is not the correct expansion.
  • ✗"Dynamic Allocation Storage Drive" is not the correct expansion.

Quick tip

Remember: DASD = Direct Access Storage Device (data reached directly by address, e.g. hard disks; IBM term); sequential access = magnetic tape; first hard disk = IBM 350 (1956, RAMAC).

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Abbreviations & Full Forms — Preparation

This question tests your understanding of Abbreviations & Full Forms, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.

This topic covers the full forms of common abbreviations used in government, banking, science, technology, defence, international relations and everyday life, such as ISRO, NABARD, SEBI, GDP, GST and UNICEF. These questions are quick marks if you have revised the most common abbreviations. Group them by field (banking, government bodies, science and technology, international organisations) and pay attention to small words such as 'of', 'for' and 'and', since wrong options often change just one word. Practise the abbreviations and full forms questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.

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