如何在显示器上显示字符？ [英] How the chars displayed on the monitor?

问题描述

存在ASCII，OEM，ANSI和Unicode表。对我来说，如果我弄错的话：据我所知，这些表格只是在纸上，即这些协议将在以后的字体中实现。



计算机加载时，会在显示屏上写入一些文本。它还将文本写入BIOS菜单中。怎么会发生？计算机的硬件中是否有一些默认字体？什么在显示器上绘制字体的字符：OS内核的特殊程序，或直接硬件？



谢谢。

解决方案

根据此页面 [ ^ ]，至少在具有Windows NT体系结构的系统上，字体由内核中的GDI处理。

Andrey Bushman问：

但BIOS怎么样？它在操作系统之前工作并显示文本。据我所知，BIOS对GDI一无所知。并且...... GDI是如何做到的？

BIOS有自己的字体。更准确地说，BIOS的一部分存储在每个图形卡中。可以通过填写专用于此信息和BIOS调用的BIOS表来修改字体。这些卡具有使用这些字体的文本模式。



这些都不是基于图形的现代操作系统中使用的，但是在操作系统使用时会使用这些字体仅运行其某些引导阶段，或者在某些配置为用作服务主机的OS中运行。服务器的Linux配置就是这种情况。但谁需要这种服务应用程序中的字体？大多数人大多数时候都记得DOS时代的那些文本模式...



例如，我知道如何使用所有这些显卡模式，但是，此时此刻，请不要不知道在Web上可以找到文档的位置。 （无论如何，我认为你不会问它。）应用程序可以很快地改变字体。例如，通过改变鼠标所在字符的字体（一次4个或更少），可以使用这些技巧模拟像素精度鼠标。



还记得现代操作系统使用Unicode。 BIOS没有。图形卡的文本模式已经过时，仅用于非常基本的功能。



请注意，BIOS本身的概念可能已经过时，最终被取代EFI。请参阅：

http://en.wikipedia.org/wiki/BIOS [< a href =http://en.wikipedia.org/wiki/BIOStarget =_ blanktitle =New Window> ^ ]，

http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface [ ^ ]。

-SA

ASCII, OEM, ANSI, and Unicode tables exist. Right me, if I am mistaken: as I understand, these tables live "on the paper" only, i.e. this are agreements which shall be implemented in the fonts later.

When the computer loads, it writes some text on the display. Also it writes the text in the BIOS menu. How it occurs? Is the computer has some "default" fonts in the hardware? What draw the chars of the font on the display: the special program of OS kernel, or the hardware directly?

Thank you.

解决方案

According to this page[^], at lest on system having the Windows NT architecture, fonts are handled by the GDI, in the kernel.

Andrey Bushman asked:

But what about BIOS? It works before the OS and displays the text too. BIOS knows nothing about the GDI, as I understand. And... How GDI does it?

BIOS has its own fonts. More exactly, the portion of the BIOS stored in each graphics card. The fonts can be modified by filling in the BIOS tables dedicated to this information and BIOS calls. The cards has the text mode where these fonts are used.

None of that is used in the modern OS based on graphics, but those fonts are used when the OS is only running some of its bootstrap phases, or in some OS configured for uses as service host. This is the case for server's configurations of Linux. But who needs fonts in such service applications? Most people mostly remember those text modes from DOS times…

I, for example, know how to work with all those graphics card modes, but, at this moment, don't know where the documentation can be found on the Web. (I don't think you are asking about it, anyway.) The application could change the fonts on the fly, very quickly. Such tricks were used, for example, to simulate pixel-accuracy mouse, by changing the fonts of the characters where the mouse is located (4 or less at a time).

Also remember that modern OS use Unicode. BIOS does not. The text modes of graphic cards are pretty much obsolete, only used for very basic functionality.

And note that the concept of BIOS itself may become obsolete, being eventually superseded by EFI. Please see:
http://en.wikipedia.org/wiki/BIOS[^],
http://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface[^].

—SA

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