Magnetic Drum


A magnetic drum is an early form of computer memory storage that uses magnetic patterns on a rotating drum to store data. It was widely used in the 1950s and 1960s as both primary and auxiliary storage in early computer systems. The magnetic drum allowed data to be accessed and rewritten multiple times, making it an essential component in the evolution of digital computing.

Key Takeaways

  1. Magnetic drums are early forms of data storage devices that store data on the surface of a rotating cylindrical drum coated with a magnetic material.
  2. These devices were primarily used in the 1950s and 1960s and were noted for their fast access time, making them popular for use in early computers and other computing devices.
  3. Although magnetic drums have been largely replaced by modern storage devices such as hard disk drives and solid-state drives, they played a significant role in the development of computer technology and laid the foundation for modern data storage.


The term “Magnetic Drum” is significant in the realm of technology because it refers to an early form of computer memory that played a crucial role in the development of computing systems.

Invented in the late 1940s, magnetic drums were used as primary storage devices in various computers and laid the foundation for modern computer memory systems.

These drums functioned by storing data through magnetizing specific segments on a spinning metal drum’s surface to represent binary information.

With their non-volatile nature, magnetic drums maintained data even in the absence of power, making them a reliable storage solution for that time.

As computing technology has evolved, magnetic drums have largely been replaced by more advanced memory systems, but they remain an essential milestone in the historical development of computer technology and data storage.


Magnetic drums serve as an early form of data storage technology with the purpose of storing and retrieving data in computer systems. These rotating cylindrical devices gained prominence during the 1950s and 1960s and were typically coated with a magnetic iron oxide material, which facilitated the data storage. Interestingly, magnetic drums were able to store information in both analog and digital formats.

The purpose of adopting magnetic drums was to enable efficient storage and retrieval of large volumes of data, which subsequently facilitated the realization of powerful computing systems and enhanced performance for many early computers. The working principle of magnetic drums relied on the rotation of the cylinder while utilizing read/write heads to either store or access data, as it rotated at high speeds. These drums were widely used for storing the main memory of computer systems, particularly for early systems like the IBM 650 series, UNIVAC 1103A, and the LGP-30.

Prominent for their non-volatile nature, magnetic drums as storage devices allowed computers to secure essential data even when the power supply was interrupted. Additionally, they played a crucial role in fulfilling early real-time tasks, such as data logging, air traffic control, and many industrial applications. However, it is essential to note that with the development of more advanced technologies, such as disk storage and semiconductor memory, magnetic drums were eventually replaced due to their larger size, slower speed, and mechanical wear and tear issues.

Examples of Magnetic Drum

IBM 650 Magnetic Drum Data-Processing Machine (1954): The IBM 650 was an early computing system that used a magnetic drum as its primary storage device, capable of storing around 10,000 characters. This machine was considered one of the first mass-produced computers, and it was widely used for data processing tasks in research institutions and businesses during the 1950s and early 1960s.

UNIVAC I Magnetic Drum (1951): The UNIVAC I was the first commercially available computer in the United States, developed by J. Presper Eckert and John W. Mauchly. It used a magnetic drum memory system that could store approximately 1,000 words of 12-digits each. The UNIVAC I was utilized by various government and commercial organizations, including the United States Census Bureau and Prudential Insurance.

DATAR (Digital Automated Tracking and Resolving) System (1950): The Royal Canadian Navy’s DATAR system was an early electronic data processing system designed for creating real-time tactical pictures of a naval battlefield. It used a magnetic drum to store the radar data received from several ships and updated the positions of vessels in real-time, enabling better naval coordination and decision-making.

Frequently Asked Questions about Magnetic Drum

1. What is a Magnetic Drum?

A magnetic drum is an early form of computer memory that uses a magnetic cylinder coated with a ferromagnetic material to store data. It is a non-volatile storage medium that was widely used in early computers as the main working memory.

2. How does a Magnetic Drum work?

A magnetic drum works by using read/write heads that move along the rotating drum surface, changing the magnetization of the ferromagnetic coating to represent binary data (0 and 1). The stored data can be read by sensing the changes in magnetic fields as the drum rotates beneath the read/write heads.

3. When were Magnetic Drums first used in computers?

Magnetic Drums were first used in computers in the late 1940s and early 1950s. They were developed as a more reliable alternative to earlier storage technologies such as punched cards and delay lines.

4. What are the advantages of Magnetic Drum storage?

Some advantages of magnetic drum storage include non-volatile data storage, relatively fast access time compared to earlier storage technologies, and reliable performance. Magnetic drums were also more compact than earlier storage solutions, making them suitable for use in early computer systems.

5. What are the disadvantages of Magnetic Drum storage?

Disadvantages of magnetic drum storage include limited storage capacity, relatively slow access times compared to later storage technologies like magnetic core memory and semiconductor memory, and mechanical wear and tear on the drum and read/write heads.

6. Why were Magnetic Drums eventually replaced in computers?

Magnetic Drums were eventually replaced in computers due to the development of more efficient storage technologies like magnetic core memory, which offered significantly higher storage capacities, faster access times, and a smaller form factor. Later, semiconductor memory like RAM and ROM became the standard for computer memory, owing to their even higher speeds and larger capacities.

Related Technology Terms

  • Data Storage
  • Read-Write Head
  • Magnetizable Coating
  • Rotating Cylinder
  • Early Computers

Sources for More Information


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