What is secondary memory and what is the difference between primary memory and secondary memory exte

Secondary memory is a type of computer memory that cannot be accessed directly by the computer's processor (CPU) and is usually used as non-volatile memory. One of the most common forms of this type of memory is the computer's hard drive, which is used to store operating systems (OS) and other programs. Other forms of secondary memory include disk drives for CDs (CDs) or digital versatile discs (***), as well as removable flash memory.

In contrast, primary memory is computer memory that is directly accessed by the CPU, usually volatile memory, and tertiary memory refers to systems outside the computer that can be directly accessed in various ways. Computer hard drives belong to secondary memoryComputer systems use different types of memory, and secondary storage is one of the most common and important types of memory.

This type of memory is often identified by how a computer system uses it and how the data is stored in it. The main feature of this type of memory is that it is not directly accessed by the CPU, but through a connection that allows the CPU to use it. This type of memory is also usually non-volatile, which means that data can be saved even when there is no power supply.

It mainly stores a large amount of file information that is difficult to accommodate in the main memory and is required for program execution. It is characterized by a large storage capacity and low storage cost, but slower access speeds. It cannot exchange information with the main memory, and it cannot exchange information directly with the processor.

It then sends various timing control signals to other functional components that are required to execute the command. Secondary storage is typically disk drives and tape drives.

Generally, the storage elements in a computer system can be divided into primary memory and auxiliary memory.

The former is further divided into random

access

memory, RAM) and read-only memory (ROM).

The latter refers to storage other than RAM and ROM, such as hard disks, disks, etc.

Secondary storage provides a larger space to store data, such as hard disks, disks, etc.

Main memory(memory) withSecondary memoryThe differences (external memory) are as follows:

1. The difference between storage time:1. Memory has the advantage of time and speed;

2. The storage time of external memory is slow.

2. Difference in storage capacity:1. The memory capacity is small, and the general memory is 4G 8G.

2. The external memory capacity is large, and the rock capacity can be expanded through the external memory.

3. Difference in storage duration:1. The memory will not be retained after power failure.

2. The external memory can be retained for a long time.

Four-chain imitation, access rights difference:1. The CPU can only access the memory directly.

2. The external storage cave must be processed by the memory CPU first.

1. Volatile vs. non-volatile.

Memory, such as random access memory (RAM), is volatile. This means that when the system loses power, data is lost. In contrast, external storage is non-volatile, so it can hold data even when there is no power supply.

2. Performance and capacity.

In most cases, external memory is much slower than memory. Unlike external memory, RAM is connected directly to the CPU via a wider and faster bus.

3. Differences in storage duration.

The memory is not retained after power failure, and the external memory can be retained for a long time.

4. Difference in access permissions:

The CPU can only directly access the memory, and the external storage can only be processed by the memory CPU first.

The main memory is memory, and the secondary memory is a hard disk or USB disk, and the read speed of the main memory is higher than that of the secondary memory, but the cost is relatively high.

There are two types of computer memory, primary memory, and secondary memory, and the important difference between them is that primary memory is generally more than secondary memory.

a) High reliability.

b) Large capacity.

c) Fast read and write speed.

d) **Low.

The internal memory is to directly exchange information with the CPU and IO devices, which is used to store temporary data when the computer is running, and the external memory is the memory that the CPU cannot directly access, which needs to exchange information with the CPU and IO devices through the memory, and is used to store a large number of programs and data including those that are not used for a long time.

For example, if we turn on the computer and start running the XP system, and the XP system is installed on the hard disk (external memory), but all the exchange data is running in memory during the run, so if your memory is large, the speed will be faster, if the speed is small, it will be slower, and when you use software such as word, it is running in memory (main memory), and then the file is stored on the hard disk (auxiliary memory).

Memory, floppy disks, hard disks, optical discs (rewritable discs, *** optical discs, etc.), removable storage media (USB flash drives, etc.), tapes, off-site storage or backup (cloud storage), etc

Secondary memory is characterized by large capacity and low costInformation can still be stored even after a power failure, which is "non-easy" memory, and most of the storage media can also store information offline.

The characteristics of secondary memory are: large storage capacity, but slow access speed; The storage time is long, but it is relatively cheap. There are several types of floppy disk capacities.

There are more types of hard disk capacity, and the current hard disk capacity of PC series microcomputer is generally between 1GB and 1000GB, and now some manufacturers have produced hard disks with larger capacity. High-end computers are generally equipped with high-speed hard disks with large capacity.

Performance metrics for secondary memory.

1. Capacity - the capacity usually refers to the total capacity of the hard disk, the unit defined by the general hard disk manufacturer is 1GB=1000MB, and the system defines 1GB=1024MB, so there will be a situation where the nominal value on the hard disk is greater than the formatted capacity, which is considered an industry practice and is a normal situation.

2. The capacity of a single disk refers to the number of bytes that can be stored on a disc, and the capacity of a single disk of a hard disk is generally more than 20GB. With the increase of the capacity of a single hard disk, the total capacity of the hard disk can already achieve hundreds of gigabytes or even a few terabytes (the capacity of the commercially purchased hard disk is 1tb, which may actually only be 1000gb, instead of 1024gb, and the real sense of 1tb = 1024gb).

The "main memory" structure was introduced to solve the problem of mismatch between the main memory and CPU speed. The "secondary memory" structure was introduced to solve the problem of insufficient main memory capacity. "Primary Memory" means adding a level of fast, but smaller, higher per bit cache storage between the CPU and Main Memory.

With the help of auxiliary software and hardware, it forms an organic whole with the main memory to make up for the lack of main memory speed.

The purpose of the "Main Memory" level is to make up for the lack of main memory capacity. It is the addition of a larger premature capacity, lower per bit**, but slower storage (called secondary memory, usually a hard disk) outside of the main memory. They rely on the role of auxiliary software and hardware to form a whole.

The "main memory" and "secondary memory" levels are often used to implement virtual memory, providing a large amount of program space to the programmer.

Introduction to hard disks

Hard disks belong to external memory, mechanical hard disks are made of metal magnetic sheets or glass magnetic sheets, and magnetic sheets have memory functions, so the data stored on the magnetic sheets, whether they are turned on or off, will not be lost. The capacity of the hard disk is very large, it has reached the terabyte level, and the size has .0 inches, etc., the interfaces are IDE, SATA, SCSI, etc., and SATA is the most common.

Portable hard disk is a storage product that uses hard disk as a storage medium and emphasizes portability. The vast majority of mobile hard disks in the market are based on standard hard disks, and only a small number of them are based on micro hard disks, but the most important factors determine whether the mainstream mobile hard disks or the shack friends are based on standard notebook hard disks.

The above content refers to Encyclopedia-Computer.