全部大写

在字体排印学中，全部大写（又作全大写）指在字母文字中，全用大写字母书写的文本或字体。“全部大写”可以用于强调单词或短语。全部大写常见于书本封面上的标题、广告以及新闻标题。较短的全部大写的文字比混合大小写的文字更加醒目。全部大写也可以用来表示首字母缩略字。
在字体排印学中已有关于全部大写文本可读性和易读性的研究。20世纪起的科学研究普遍表明全部大写的可读性和易读性比小写文本要差。同时，由于全部大写常常被用来记录说话人的吼叫的文化原因，将文本转换为全部大写使其看起来更加地有威吓意味且使人感到厌恶。全部大写文本在漫画书中很常见，在老式的电传系统和无线电通信系统中也很常见，这些系统通常根本不会区别字母的大小写。
在专业性文件中，人们通常更喜欢使用小型大写字母的形式来使用全部大写，以此强调关键词或者首字母缩略词（亦可用斜体或更少见的粗体）。同时，习惯上使用全部大写时会轻微地加宽字母间距（大约点高度的10%）。一些数字字体由于这个原因自动包含了大写字母的间距。
与吼叫的联系.
用全部大写书写的文本信息在社群媒体中时常被认为是吼叫或其他不礼貌的争论行为，这在1980年代网路化电脑出现起成为主流的解释。然而，类似的解释在电脑时代前的书面资料早已存在，某些资料甚至已有一世纪以上的历史。在大量的文学作品中，都给出了用大写字母进行呼喊的例子。以下资料可能与大写字母的历史有关从Stack Exchange discussion on all-caps 可看出:
用法.
纸媒.
在小写字母于公元8世纪发展起来之前，用拉丁字母写的文本只有一种形式，即现在认为的大写字母。
在20世纪20年代之前，大写字母被广泛地用于报纸的新闻标题上。到20世纪90年代，超过四分之三的西方报纸已经在使用小写字母印刷新闻标题了。关于全部大写使用的讨论聚焦于全部大写更好的强调性和小写字母更好的易读性。柯林·威尔顿的一项研究召集了224个阅读者分析新闻标题的样式，最后得出了“大写字母新闻标题明显比小写字母行文标题的易读性更低”的结论
姓氏.
全部大写的姓氏常见于法语国家，用来将姓氏和余下的其他名字区别开来。这一行为在国际赛事及日语中当用罗马字来书写姓名时亦常见。
军事信息系统.
2013年4月，美国海军废除了全部大写的信息系统，这个系统始于19世纪50年代，那时电传只有大写字母的形式。由全部大写向大小写混合的信息系统的转换帮助美国海军每年节省约2千万美元，也使其更好地与现代网络协议对接。
可读性.
According to Tinker, “As early as 1914, Starch reported that material set in Roman lower case was read somewhat faster than similar material printed in all capitals.” Another study in 1928 showed that “all-capital text was read 11.8 percent slower than lower case, or approximately 38 words per minute slower,” and that “nine tenths of adult readers consider lower case more legible than all capitals.”
A 1955 study by Miles Tinker showed that “all-capital text retarded speed of reading from 9.5 to 19.0 percent for the 5 and 10-minute time limits, and 13.9 percent for the whole 20-minute period.” Tinker concluded that, “Obviously, all-capital printing slows reading to a marked degree in comparison with Roman lower case.”
Tinker provides the following explanations for why all capital printing is more difficult to read: Text in all capitals covers about 35 percent more printing surface than the same material set in lower case. This would tend to increase the reading time. When this is combined with the difficulty in reading words in all-capital letters as units, the hindrance to rapid reading becomes marked. In the eye-movement study by Tinker and Patterson, the principal difference in oculomotor patterns between lower case and all capitals was the very large increase in number of fixation pauses for reading the all-capital print.
All caps text should be eliminated from most forms of composition, according to Tinker: “Considering the evidence that all-capital printing retards speed of reading to a striking degree in comparison with lower case and is not liked by readers, it would seem wise to eliminate such printing whenever rapid reading and consumer (reader) views are of importance. Examples of this would include any continuous reading material, posters, bus cards, billboards, magazine advertising copy, headings in books, business forms and records, titles of articles, books and book chapters, and newspaper headlines.”
Colin Wheildon stated that there is an "apparent consensus" that lower-case text is more legible, but that some editors continue to use all caps in text regardless. In his studies of all caps in headlines, he states that, "Editors who favor capitals claim that they give greater emphasis. Those who prefer lower case claim their preferences gives greater legibility." Wheildon, who informs us that "When a person reads a line of type, the eye recognizes letters by the shapes of their upper halves," asserts that recognizing words in all caps "becomes a task instead of a natural process." His conclusions, based on scientific testing in 1982–1990, are: "Headlines set in capital letters are significantly less legible than those set in lower case."
John Ryder, in the "Case for Legibility", stated that "Printing with capital letters can be done sufficiently well to arouse interest and, with short lines, reading at a slowed speed is possible – but in principle too many factors of low legibility are involved."
Other critics are of the opinion that all caps letters in text are often "too tightly packed against each other".
An antiquated practice that still remains in use, especially by older American lawyers who grew up before the arrival of computers, is to use all caps text for text that is legally required to be emphasised and clearly readable. The practice dates to the period of typewriters, which generally did not offer bold text, small capitals, or the opportunity to add marginal notes emphasising key points. Legal writing expert has described the practice as 'ghastly'. In 2002, a US court spoke out against the practice, ruling that simply making text all-capitals has no bearing on whether it is clear and easily readable:
Lawyers who think their caps lock keys are instant “make conspicuous” buttons are deluded. In determining whether a term is conspicuous, we look at more than formatting. A term that appears in capitals can still be inconspicuous if it is hidden on the back of a contract in small type. Terms that are in capitals but also appear in hard-to-read type may flunk the conspicuousness test. A sentence in capitals, buried deep within a long paragraph in capitals will probably not be deemed conspicuous...it is entirely possible for text to be conspicuous without being in capitals.