Question

How does a magnetic core memory store and retrieve digital data?

Answer 1

Magnetic core memory, used primarily in early computers, stores data using tiny magnetic rings called magnetic cores. Each core represents one bit of data, with its magnetic orientation indicating whether the bit is a 0 or a 1.

### Storage:
1. **Magnetic Cores**: Each core is made of a ferromagnetic material and is threaded by wires. The state of each core (magnetized in one direction for a 1, or the opposite direction for a 0) is what stores the data.
2. **Wiring**: A grid of horizontal and vertical wires is used, with each core located at the intersection of a specific wire pair.
3. **Writing Data**: To write data to a core, a current is passed through the appropriate wires, creating a magnetic field that flips the core's orientation, thereby storing a 1 or a 0.

### Retrieval:
1. **Reading Data**: To read the data, a small current is sent through the wires connected to the core in question. If the core is magnetized in one direction, it will induce a voltage in the sensing wire; if it's in the opposite direction, it won't.
2. **Sensing**: The induced voltage indicates whether the core is a 1 or a 0, allowing the system to retrieve the stored data.

### Advantages and Disadvantages:
- **Advantages**: Non-volatile (retains data when powered off), durable, and relatively fast.
- **Disadvantages**: Bulky and complex compared to modern semiconductor memory technologies.

Magnetic core memory was widely used until the advent of more compact and faster technologies, such as dynamic RAM (DRAM).

Answer 2

Magnetic core memory is an early form of computer memory that was widely used from the 1950s to the 1970s. It consists of tiny magnetic cores, each representing a single bit of data. Here's how it works:

### **Storing Data**

1. **Magnetic Cores**: Each core is a small ring of magnetic material (like ferrite) through which wires are threaded. The core can be magnetized in one of two directions, representing binary 0 or 1.

2. **Writing Data**: To write data to the core memory, a current is passed through wires (one set for each bit). By sending a current through the appropriate wires, the core can be magnetized in one direction or the other, corresponding to a 0 or 1. This process involves the use of a specific arrangement of wires called "select" and "write" lines, which pass through the cores.

### **Retrieving Data**

1. **Reading Data**: To read data, a current is sent through the "sense" wire of the core. If the core was magnetized in one direction, it will cause a small voltage change in the sense wire, which can be detected and interpreted as a binary 0 or 1. If the core was magnetized in the opposite direction, the voltage change will be different, representing the opposite binary value.

2. **Sense Amplifiers**: The small voltage changes caused by the core's magnetic orientation are amplified by sense amplifiers to make them readable by the computer's circuitry.

### **Key Points**

- **Non-Volatility**: Magnetic core memory is non-volatile, meaning it retains data even when power is off.
- **Durability**: It is physically robust and can withstand environmental stresses.
- **Sequential Access**: Reading and writing are not instantaneous and can involve delays due to the mechanical nature of the memory.

Magnetic core memory has largely been replaced by semiconductor memory in modern computers, but it was a significant advancement in the early days of computing.