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This article will explain in detail what the network word null means. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

The original meaning of the network word null is empty, which usually means null, no result, or empty collection in computers, and programs usually use null pointers to represent conditions; the use of null pointers at the end of a list of unknown lengths or without performing certain actions can be compared with the pointing values in nullable types and option types.

Null originally means "empty; elements only have zero" meaning. The computer usually represents a null value, no result, or an empty collection. Programs usually use null pointers to represent conditions, such as the end of a list of unknown lengths or not performing certain actions; the use of such null pointers can be compared with the pointing values in nullable types and option types.

Null pointers should not be confused with uninitialized pointers: make sure that null pointers are compared to any pointers to valid objects. However, depending on the language and implementation, uninitialized pointers may not have any such guarantees.

Extended data

In fact, dereferencing a null pointer may cause an attempt to read or write from memory that has never been mapped, triggering a segmentation error or memory access violation. This may appear as a program crash or be converted to a software exception that can be caught by the program code.

However, this is not the case in some cases. For example, in x86 real mode, the address 0000displacement 0000 is readable and usually writable, and dereferencing a pointer to that address is a fully valid but usually unneeded operation, which can lead to undefined but non-crashing behavior in the application.

Sometimes dereferencing a pointer with a zero address is useful and explicit; for example, BIOS code written in C for a 16-bit real-mode x86 device can write to IDT at the physical address 0 of the machine by dereferencing the null pointer. The compiler can also optimize null pointer dereferencing to avoid segmentation errors but cause other unwanted behavior.

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