In general terms, descriptors are some attributes of objects for which the corresponding behavior is defined. When they are accessed, the specified attributes are obtained, set, or removed from the dictionary. In simple terms, these are special keywords that define the behavior of an object, its properties or structure. The article will consider several options for descriptors. This will allow you to more accurately understand their essence and purpose.
In the hypertext markup language, which is used to create static web pages, descriptors are nothing more than tags. In this environment, they act as labels, thanks to which the text placed between them is displayed in a certain way. This is how the design and arrangement of elements on the page is formed.
As a rule, the specificity of the language determines the presence of an opening descriptor and a closing one. Everything in between is subject to change.
A descriptor can have attributes, i.e. certain properties. Their syntax is: attribute name=attribute value.
Following the general logic, descriptors in HTML are the identification marks of objects. With their help, you can control the appearance, interact with the page andassign special meanings to it.
In processors, descriptors are a special structure with which various transitions are made. Its structure looks like this:
- Offset. Can shift code procedure.
- Selector. Reflects a kind of label where the procedure should go.
- Number of parameters.
Java EE has the concept of a deployment descriptor. It defines how the servlet will be deployed. Basically, it is a configuration file containing settings, properties, and hardware requirements.
In web applications, such a file should be called web.xml according to the rules and located in a specific folder.
On operating systems, files must first be accessed in order to work with them. This can be done via a file descriptor. In this example, it acts as a kind of label that indicates the process that created the I / O stream.
The Windows operating system allows you to access the handle using the CreateFile function. It can be used later when working with the required file.
On Unix systems, the file descriptor is numeric. 0 - standard input of the terminal process, 1 - its output, 2 - diagnostic stream. In addition to numeric representations, symbolic constants defined by the specification can be used.
After any window is created in the system, it is assigned a certain handle. The data types used in it are HWND. The programmer, when creating an application, needs to correctly use them to access window elements.
The program can get the handle by calling the FindWindow function. It will be able to find it by the name of the class or object of the window and return the value of the handle.
To check if the identification went through correctly, you should use the IsWindow function.
Error number 1400
This problem is common in the Windows family of operating systems. When it appears, it may also include a short description - an invalid window handle. Or there may be such a wording - “Error_invalid_window_handle” or 0x578.
How to fight and what does an invalid descriptor mean? Depending on the context of the object, different measures need to be taken.
In any case, you should immediately go through the standard measures taken for all problems with the system:
- computer restart;
- running and error scanning with System File Integrity Checker;
- check your computer for viruses.
If the basic steps didn't work, it might be worth uninstalling and reinstalling the app that's causing the crash.
Another reliable way to quickly restore the system to working capacity is to roll it back using standard tools. After using System Restore, it will revert tolast valid backup, provided it was previously created.
When an error might occur
In most cases, the invalid handle error is caused by a bug in the installed software. Therefore, you should carefully monitor what appears on the computer from the software. It is also necessary to periodically update all available software and monitor its status. At the same time, it is worth arming yourself with good anti-virus software.
The article presented the general principles of descriptors in various programming languages and operating systems, their functions, properties and types. As a rule, this term is mainly used by programmers and developers to identify objects and elements for subsequent access and control.
It also became clear that this is an invalid descriptor. As it turned out, this is a common problem in the Windows environment, in most cases it can be solved with simple manipulations.