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sources/talk/20180623 The IBM 029 Card Punch.md

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-The IBM 029 Card Punch
-======
-Lines of code longer than 80 characters drive me crazy. I appreciate that this is pedantic. I’ve seen people on the internet make good arguments for why the 80-character limit ought to be respected even on our modern Retina-display screens, but those arguments hardly justify the visceral hatred I feel for even that one protruding 81st character.
-
-There was once a golden era in which it was basically impossible to go over the 80-character limit. The 80-character limit was a physical reality, because there was no 81st column for an 81st character to fit in. Any programmers attempting to name a function something horrendously long and awful would discover, in a moment of delicious, slow-dawning horror, that there literally isn’t room for their whole declaration.
-
-This golden era was the era of punch card programming. By the 1960s, IBM’s punch cards had set the standard and the standard was that punch cards had 80 columns. The 80-column standard survived into the teletype and dumb terminal era and from there embedded itself into the nooks and crannies of our operating systems. Today, when you launch your terminal emulator and open a new window, odds are it will be 80 characters wide, even though we now have plenty of screen real estate and tend to favor longer identifiers over inscrutable nonsense like `iswcntrl()`.
-
-If questions on Quora are any indication, many people have trouble imagining what it must have been like to program computers using punch cards. I will admit that for a long time I also didn’t understand how punch card programming could have worked, because it struck me as awfully labor-intensive to punch all those holes. This was a misunderstanding; programmers never punched holes in cards the same way a train conductor does. They had card punch machines (also known as key punches), which allowed them to punch holes in cards using a typewriter-style keyboard. And card punches were hardly new technology—they were around as early as the 1890s.
-
-One of the most widely used card punch machines was the IBM 029. It is perhaps the best remembered card punch today.
-
-![][1]
-
-The IBM 029 was released in 1964 as part of IBM’s System/360 rollout. System/360 was a family of computing systems and peripherals that would go on to dominate the mainframe computing market in the late 1960s. Like many of the other System/360 machines, the 029 was big. This was an era when the distinction between computing machinery and furniture was blurry—the 029 was not something you put on a table but an entire table in itself. The 029 improved upon its predecessor, the 026, by supporting new characters like parentheses and by generally being quieter. It had cool electric blue highlights and was flat and angular whereas the 026 had a 1940s rounded, industrial look. Another of its big selling points was that it could automatically left-pad numeric fields with zeros, demonstrating that JavaScript programmers were not the first programmers too lazy to do their own left-padding.
-
-But wait, you might say—IBM released a brand-new card punch in 1964? What about that photograph of the Unix gods at Bell Labs using teletype machines in, like, 1970? Weren’t card punching machines passé by the mid- to late-1960s? Well, it might surprise you to know that the 029 was available in IBM’s catalog until as late as 1984. In fact, most programmers programmed using punch cards until well into the 1970s. This doesn’t make much sense given that there were people using teletype machines during World War II. Indeed, the teletype is almost of the same vintage as the card punch. The limiting factor, it turns out, was not the availability of teletypes but the availability of computing time. What kept people from using teletypes was that teletypes assumed an interactive, “online” model of communication with the computer. Before Unix and the invention of timesharing operating systems, your interactive session with a computer would have stopped everyone else from using it, a delay potentially costing thousands of dollars. So programmers instead wrote their programs offline using card punch machines and then fed them into mainframe computers later as batch jobs. Punch cards had the added benefit of being a cheap data store in an era where cheap, reliable data storage was hard to come by. Your programs lived in stacks of cards on your shelves rather than in files on your hard drive.
-
-So what was it actually like using an IBM 029 card punch? That’s hard to explain without first taking a look at the cards themselves. A typical punch card had 12 rows and 80 columns. The bottom nine rows were the digit rows, numbered one through nine. These rows had the appropriate digit printed in each column. The top three rows, called the “zone” rows, consisted of two blank rows and usually a zero row. Row 12 was at the very top of the card, followed by row 11, then rows zero through nine. This somewhat confusing ordering meant that the top edge of the card was called the 12 edge while the bottom was called the nine edge. A corner of each card was usually clipped to make it easier to keep a stack of cards all turned around the right way.
-
-![][2]
-
-When they were first invented, punch cards were meant to be punched with circular holes, but IBM eventually realized that they could fit more columns on a card if the holes were narrow rectangles. Different combinations of holes in a column represented different characters. For human convenience, card punches like the 029 would print each column’s character at the top of the card at the same time as punching the necessary holes. Digits were represented by one punched hole in the appropriate digit row. Alphabetical and symbolic characters were represented by a hole in a zone row and then a combination of one or two holes in the digit rows. The letter A, for example, was represented by a hole in the 12 zone row and another hole in the one row. This was an encoding of sorts, sometimes called the Hollerith code, after the original inventor of the punch card machine. The encoding allowed for only a relatively small character set; lowercase letters, for example, were not represented. Some clever engineer today might wonder why punch cards didn’t just use a binary encoding—after all, with 12 rows, you could encode over 4000 characters. The Hollerith code was used instead because it ensured that no more than three holes ever appeared in a single column. This preserved the structural integrity of the card. A binary encoding would have entailed so many holes that the card would have fallen apart.
-
-Cards came in different flavors. By the 1960s, 80 columns was the standard, but those 80 columns could be used to represent different things. The basic punch card was unlabeled, but cards meant for COBOL programming, for example, divided the 80 columns into fields. On a COBOL card, the last eight columns were reserved for an identification number, which could be used to automatically sort a stack of cards if it were dropped (apparently a perennial hazard). Another column, column seven, could be used to indicate that the statement on this card was a continuation of a statement on a previous card. This meant that if you were truly desperate you could circumvent the 80-character limit, though whether a two-card statement counts as one long line or just two is unclear. FORTRAN cards were similar but had different fields. Universities often watermarked the punch cards handed out by their computing centers, while other kinds of designs were introduced for special occasions like the [1976 bicentennial][3].
-
-Ultimately the cards had to be read and understood by a computer. IBM sold a System/360 peripheral called the IBM 2540 which could read up to 1000 cards per minute. The IBM 2540 ran electrical brushes across the surface of each card which made contact with a plate behind the cards wherever there was a hole. Once read, the System/360 family of computers represented the characters on each punch card using an 8-bit encoding called EBCDIC, which stood for Extended Binary Coded Decimal Interchange Code. EBCDIC was a proper binary encoding, but it still traced its roots back to the punch card via an earlier encoding called BCDIC, a 6-bit encoding which used the low four bits to represent a punch card’s digit rows and the high two bits to represent the zone rows. Punch card programmers would typically hand their cards to the actual computer operators, who would feed the cards into the IBM 2540 and then hand the printed results back to the programmer. The programmer usually didn’t see the computer at all.
-
-What the programmer did see a lot of was the card punch. The 029 was not a computer, but that doesn’t mean that it wasn’t a complicated machine. The best way to understand what it was like using the 029 is to watch [this instructional video][4] made by the computing center at the University of Michigan in 1967. I’m going to do my best to summarize it here, but if you don’t watch the video you will miss out on all the wonderful clacking and whooshing.
-
-The 029 was built around a U-shaped track that the punch cards traveled along. On the right-hand side, at the top of the U, was the card hopper, which you would typically load with a fresh stack of cards before using the machine. The IBM 029 worked primarily with 80-column cards, but the card hopper could accommodate smaller cards if needed. Your punch cards would start in the card hopper, travel along the line of the U, and then end up in the stacker, at the top of the U on the left-hand side. The cards would accumulate there in the order that you punched them.
-
-To turn the machine on, you flipped a switch under the desk at about the height of your knees. You then pressed the “FEED” key twice to get cards loaded into the machine. The business part of the card track, the bottom of the U, was made up of three separate stations: On the right was a kind of waiting area, in the middle was the punching station, and on the left was the reading station. Pressing the “FEED” key twice loaded one card into the punching station and one card into the waiting area behind it. A column number indicator right above the punching station told you which column you were currently punching. With every keystroke, the machine would punch the requisite holes, print the appropriate character at the top of the card, and then advance the card through the punching station by one column. If you punched all 80 columns, the card would automatically be released to the reading station and a new card would be loaded into the punching station. If you wanted this to happen before you reached the 80th column, you could press the “REL” key (for “release”).
-
-The printed characters made it easy to spot a mistake. But fixing a mistake, as the University of Michigan video warns, is not as easy as whiting out the printed character at the top of the card and writing in a new one. The holes are all that the computer will read. Nor is it as easy as backspacing one space and typing in a new character. The holes have already been punched in the column, after all, and cannot be unpunched. Punching more holes will only produce an invalid combination not associated with any character. The IBM 029 did have a backspace button that moved the punched card backward one column, but the button was placed on the face of the machine instead of on the keyboard. This was probably done to discourage its use, since backspacing was so seldom what the user actually wanted to do.
-
-Instead, the only way to correct a mistake was scrap the incorrect card and punch a new one. This is where the reading station came in handy. Say you made a mistake in the 68th column of a card. To fix your mistake, you could carefully repunch the first 67 columns of a new card and then punch the correct character in the 68th column. Alternatively, you could release the incorrect card to the reading station, load a new card into the punching station, and hold down the “DUP” key (for duplicate) until the column number indicator reads 68. You could then correct your mistake by punching the correct character. The reading station and the “DUP” key together allowed IBM 029 operators to easily copy the contents of one card to the next. There were all sorts of reasons to do this, but correcting mistakes was the most common.
-
-The “DUP” key allowed the 029’s operator to invoke the duplicate functionality manually. But the 029 could also duplicate automatically where necessary. This was particularly useful when punched cards were used to record data rather than programs. For example, you might be using each card to record information about a single undergraduate university student. On each card, you might have a field that contains the name of that student’s residence hall. Perhaps you find yourself entering data for all the students in one residence hall at one time. In that case, you’d want the 029 to automatically copy over the previous card’s residence hall field every time you reached the first column of the field.
-
-Automated behavior like this could be programmed into the 029 by using the program drum. The drum sat upright in the middle of the U above the punching station. You programmed the 029 by punching holes in a card and wrapping that card around the program drum. The punched card allowed you to specify the automatic behavior you expected from the machine at each column of the card currently in the punching station. You could specify that a column should automatically be copied from the previous card, which is how an 029 operator might more quickly enter student records. You could also specify, say, that a particular field should contain numeric or alphabetic characters, or that a given field should be left blank and skipped altogether. The program drum made it much easier to punch schematized cards where certain column ranges had special meanings. There is another [“advanced” instructional video][5] produced by the University of Michigan that covers the program drum that is worth watching, provided, of course, that you have already mastered the basics.
-
-Watching either of the University of Michigan videos today, what’s surprising is how easy the card punch is to operate. Correcting mistakes is tedious, but otherwise the machine seems to be less of an obstacle than I would have expected. Moving from one card to the next is so seamless that I can imagine COBOL or FORTRAN programmers forgetting that they are creating separate cards rather than one long continuous text file. On the other hand, it’s interesting to consider how card punches, even though they were only an input tool, probably limited how early programming languages evolved. Structured programming would eventually come along and encourage people to think of entire blocks of code as one unit, but I can see how punch card programming’s emphasis on each line made structured programming hard to conceive of. It’s no wonder that punch card programmers were not the ones that decided to enclose blocks with single curly braces entirely on their own lines. How wasteful that would have seemed!
-
-So even though nobody programs using punch cards anymore, every programmer ought to [try it][6] at least once—if only to understand why COBOL and FORTRAN look the way they do, or how 80 characters somehow became everybody’s favorite character limit.
-
-If you enjoyed this post, more like it come out every two weeks! Follow [@TwoBitHistory][7] on Twitter or subscribe to the [RSS feed][8] to make sure you know when a new post is out.
-
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-via: https://twobithistory.org/2018/06/23/ibm-029-card-punch.html
-
-作者：[Two-Bit History][a]
-选题：[lujun9972][b]
-译者：[译者ID](https://github.com/译者ID)
-校对：[校对者ID](https://github.com/校对者ID)
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-本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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-[a]: https://twobithistory.org
-[b]: https://github.com/lujun9972
-[1]: https://twobithistory.org/images/ibm029_front.jpg
-[2]: https://twobithistory.org/images/card.png
-[3]: http://www.jkmscott.net/data/Punched%20card%20013.jpg
-[4]: https://www.youtube.com/watch?v=kaQmAybWn-w
-[5]: https://www.youtube.com/watch?v=SWD1PwNxpoU
-[6]: http://www.masswerk.at/keypunch/
-[7]: https://twitter.com/TwoBitHistory
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translated/talk/20180623 The IBM 029 Card Punch.md

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+IBM 029 型打孔机
+======
+我知道这很学院派，可一行超过 80 个字符的代码还是让我抓狂。我也在网上见过不少人认为即在现代视网膜屏幕下也应当采用行长度为 80 个字符的标准，可他们都不理解我对破坏这一标准的怒火，就算 1 个字符也不行。
+
+在这一标准的黄金时期，一行代码的长度几乎不会超过 80 个字符的限制。在那时，这一限制是物理的，没有第 81 列用于存放第 81 个字符。每一个试图把函数名起的又长又臭的程序员都会在短暂的愉悦后迎来更多的麻烦，而这仅仅时因为没有足够的空间放下整个函数的声明。
+
+这一黄金时期也是打孔卡编程时期。在 20 世纪 60 年代， IBM 打孔卡的特性，也就是打孔卡的长度为 80 个字符成为了打孔卡的标准。这一标准在后来的电传打字机和哑终端时期得以延续，并逐渐成为操作系统中隐藏的细节。时至今日，即使我们用上了更大、更好的屏幕，偏向于使用更长的标识符而不是类似 `iswcntrl()` 这样令人难以猜测的函数名，可当你打开新的终端模拟器窗口时，默认的宽度依然是 80 个字符。
+
+从 Quora 上的很多问题中可以发现，很多人并不能想象如何使用打孔卡给计算机编程。我承认，在很长的一段时间里我也不能理解卡编程成是如何工作的，因为这让我想到有很多劳工不停的给这些打孔卡打孔。当然，这是一个误解，程序员不需要亲自给打孔卡打孔，就像是火车调度员不用亲自扳道岔。程序员们有打孔机(也被称为<ruby>键控打孔机<rt>key punches</rt></ruby>)，这让他们可以使用打字机式的键盘给打孔卡打孔。这样的设备在 19 世纪 90 年代时就已经不是什么新技术了。
+
+那时，最为广泛使用的打孔机之一便是 IBM 029 型打孔机。就算在今天，它也许是最棒的打孔机。
+
+![][1]
+
+IBM 029 型打孔机在 1964 年作为 IBM 的 System/360 大型电脑的配件发售的。 System/360 是计算系统与外设所组成的一个系列，在 20 世纪 60 年代晚期，它几乎垄断了整个大型计算机市场。就像其它 System/360 外设一样， 029 型打孔机也是个大块头。那时，计算机和家具的界限还很模糊，但 029 型打孔机可不是那种会占领你的整张桌子的机器。它改进自 026 型打孔机，增加了新的字符支持，如括号，总体上也更加安静。与前辈 026 型所展出 20 世纪 40 年代的圆形按钮与工业化的样貌相比， 029 型的按键方正扁平、功能按键还有酷炫的蓝色高亮提示。它的另一个重要买点是它能够在<ruby>数字区<rt>numeric fields</rt></ruby>左侧自动的填充 0 ，这证明了 JavaScript 程序员不是第一批懒得自己做<ruby>左填充<rt>left-padding</rt></ruby>的程序员。
+(译者注：这项功能需要额外的 4 张 [<ruby>标准模块系统卡<rt>SMS card</rt></ruby>](https://en.wikipedia.org/wiki/IBM_Standard_Modular_System)才能使用。例如数字区长度为 6 时，操作员只需要输入 73 ，打孔机会自动填充起始位置上的 4 个 0 ，故最终输出 000073。[更多信息](https://en.wikipedia.org/wiki/Keypunch#IBM_029_Card_Punch))
+
+等等！你说的是 IBM 在 1964 年发布了全新的打孔机？你知道那张在贝尔实验室拍摄的 Unix 之父正在使用电传打字机的照片吗？那是哪一年的来着？1970？打孔机不是应该在 20 世纪 60 年代中期到晚期时就过时了吗？是的，你也许会奇怪，为什么直到 1984 年， IBM 的产品目录中才出现 029 型打孔机的身影。事实上，直到 20 世纪 70 年代，大多数程序员仍然在使用打孔卡编程。其实二战期间就已经有人在用电传打字机了，可那时并没能普及。客观的讲，电传打字机几乎和打孔卡一样古老。也许和你想象的恰恰相反，并不是电传打字机本身限制了他的普及，而是计算时间。人们拒绝使用电传打字机的原因是，它是可交互的，它和计算机使用<ruby>“在线”的传输方式<rt>"online" mode of communication</rt></ruby>。在以 Unix 为代表的分时操作系统被发明前，你和电脑的交互会被任何人的使用而打断，而这一点延迟通常意味着几千美元的损失。所以程序员们普遍选择离线地使用打孔机编程，再将打孔卡放入大型计算机中，作为<ruby>批任务<rt>batch job</rt></ruby>执行。在那时，还没有即廉价又可靠的存储设备，可打孔卡的廉价优势已经足够让他成为那时最流行的数据存储方式了。那时的程序是书架上一落的打孔卡而不是硬盘里的一堆文件。
+
+那么实际使用 IBM 029 型打孔机是个什么样子呢？这很难向没有实际看过打孔卡的人解释。一张打孔卡通常有12行80列。打孔卡下面是从 1 到 9 的<ruby>数字行<rt>digit rows</rt></ruby>，打孔卡上的每一列都有这些行所对应的数字。最上面的三行是<ruby>空间行<rt>"zone" rows</rt></ruby>，通常由两行空白行和一行 0 行组成。第 12 行是打孔卡最顶层的行，接下来是 11 行，随后是从数字 0 到 9 所在的行。这个有点让人感到困惑的顺序的原因是打孔卡的上边缘被称为<ruby>12 边<rt>12 edge</rt></ruby>、下边缘被称为 <ruby>9 边<rt>9 edge</rt></ruby>。那时，为了让打孔卡便于整理，常常会剪去打孔卡的一个角。
+
+![][2]
+(译者注：可参考[EBCDIC 编码](https://zh.wikipedia.org/wiki/EBCDIC))
+
+在打孔卡发明之初，孔洞的形状是圆形的，但是 IBM 最终意识到如果使用窄长方形作为孔洞，一张卡就可以放下更多的列了。每一列中孔洞的不同组合就可以表达不同的字符。像 029 型这样的拥有人性化设计的打孔机除了完成本质的打孔任务外，还会在打孔卡最上方打印出每一列所对应的字符。输入是数字就在对应的数字行上打孔。输入的是字母或符号就用一个在空间列的孔和一或俩个在数字列的孔的组合表示，例如字母 A 就用一个在第 12 空间行的空和一个数字 1 所在行的孔表示。这是一种顺序编码，在第一台打孔机被发明后，也叫 Hollerith 编码。这种编码只能表示相对较小的一套字符集，小写字母就没有包含在这套字符集中，但它的优势在于保留了打孔卡的结构强度。如果直接使用二进制编码，打孔卡可能会因为孔洞过于密集而断裂。
+
+打孔卡也有不同。在 20 世纪 60 年代，80 列虽然是标准，但表达的方式不一定相同。基础打孔卡是无标注的，但用于 COBOL 编程的打孔卡会把最后的 8 列保留，供标识数保存使用。这一标识数可以在打孔卡被打乱 (例如一叠打孔卡掉在地上了) 后用于自动排序。此外，第 7 列被用于表示本张打孔卡上的是否是上一张打孔卡一起构成一条语句。也就是说当你真的对 80 字符的限制感到绝望的时候，还可以用两张卡甚至更多的卡拼接成一条长语句。用于 FORTRAN 编程的打孔卡和 COBOL 打孔卡类似，但是定义的列不同。大学里使用的打孔卡通常会由其计算机中心加上水印，其他的设计则会在如 [1976 年美国独立 200 周年][3] 的特殊场合才会加入。
+
+最终，这些打孔卡都要被计算机读取和计算。 IBM 出售的 System/360 大型计算机的外设 IBM 2540 可以以每分钟 1000 张打孔卡的速度读取这些卡片。IBM 2540 使用电刷扫过每张打孔卡，电刷通过孔洞就可以接触到卡片后面的金属板完成一次读取。一旦读取完毕， System/360 大型计算机就会把每张打孔卡上的数据使用一种定长的 8 位编码保存，这种编码是<ruby>扩展的二进制十数交换码<rt>Extended Binary Coded Decimal Interchange Code</rt></ruby>，简写为 EBCDIC 编码。它的源自于早期打孔卡所使用的 BCDIDC 编码，这一 6 位编码使用低 4 位表示数字行，高 2 位表示空间行。程序员们在打孔卡上编写玩程序后，会把卡片们交给计算机操作员，操作员们会把这些卡片放入 IBM 2540 ，再把打印结果交给程序员。那时的程序员大多都没有见过计算机长什么样。
+
+程序员们真正能见到的是很多打孔机。 029 型打孔机虽然不是计算机，但这并不意味着它不是一台复杂的机器。看看这个由<ruby>密歇根大学<rt>University of Michigan</rt><ruby>在 1967 年制作的[教学视频][4]，你就能更好的理解使用一台 029 型打孔机是什么情形了。我会尽可能在这里总结这段视频，但如果你不去亲自看看的话，你会错过许多惊奇和感叹。
+
+029 型打孔机的结构围绕着一个打孔卡穿过机器的 U 形轨道开始。使用打孔机时，右手边也就是 U 形轨道的右侧顶部是<ruby>进卡卡槽<rt>hopper</rt></ruby>，使用前通常在里面放入一叠未使用的打孔卡。虽然 029 型打孔机主要使用 80 列打孔卡，但在需要的情况下也可以使用更小号的打孔卡。在打孔机的使用过程中，打孔卡离开轨道右上端的进卡卡槽，顺着 U 形轨道移动并最终进入左上端的<ruby>出卡卡槽<rt>stacker</rt></ruby>。这一流程可以保证出卡卡槽中的打孔卡按打孔时的先后顺序排列。
+
+029 型打孔机的开关在桌面下膝盖高度的位置。在开机后，连按两次 “<ruby>装入<rt>FEED</rt><ruby>” 键让机器自动将打孔卡从进卡卡槽中取出并移动到机器内。 U 形轨道的底部是打孔机的核心区域，它由三个部分组成：右侧是等待区，中间是打孔操作区，左侧是阅读区。连按两次 “装入” 键，机器就会把一张打孔卡装入打孔机的打孔操作区，另一张打孔卡进入等待区。在打孔操作区上方有一个列数指示器来显示当前打孔所在的列的位置。这时，每按下一个按键，机器就会在打孔卡对应的位置打孔并在卡片的顶部打印按键对应的字符，随后将打孔卡向左移动一列。如果一张卡片的 80 列全部被打上了数据，这张卡片会被打孔操作区自动释放并进入阅读区，同时，一张新的打孔卡会被装入打孔操作区。如果没有打完全部的 80 列，可以使用 “<ruby>释放<rt>REL (for release)</rt><ruby>” 键完成上面的操作。
+
+在打孔卡上打印对应的字符这一设计让人很容易分辨出错误。但就像密歇根大学的视频中警告的那样，打孔卡上修正一个错误可不像擦掉一个打印的字符然后再写上一个新的那样容易，因为计算机只会根据卡片上的孔来读取信息。因为被打出的孔不能被<ruby>复原<rt>unpunched</rt><ruby>，所以并不能直接退回一列然后再打上一个新的字符。打出更多的孔也只能让这一列的组合变成一个无效字符。 IBM 029 型打孔机上虽然有一个可以让打孔卡回退一列的退格按键，但这个按键被放置在机器上而非在键盘上。这样的设计也许是为了阻止这个按键的使用，因为实际上很少有用户需要这个功能。
+
+实际上，只有废弃错误的打孔卡再在新的打孔卡上重新打孔这一种修正错误的方式。这就是阅读区的用武之处了。当你发现打孔卡上的第 68 列出错时，你需要在新的打孔卡上小心的给前 67 列打孔，然后给第 68 列打上正确的字母。另一种操作方式是把带有错误信息的打孔卡放在阅读区，同时在打孔操作区载入一张新的打孔卡，然后按下 “<ruby>重复<rt>DUP (for duplicate)</rt></ruby>” 按键直到列数指示器显示 68 列。这时按下正确的字符来修正错误。阅读区和重复按键使得 029 型打孔机很容易复制打孔卡上的内容。当然，这一功能的使用可能有各种各样的原因，但改错是最常见的。
+
+“重复”按键允许 029 型打孔机的操作员手动调用重复的函数。但是 029 型打孔机还可以设置为自动重复。当用于记录数据而不是编程时，这项功能十分有效。举个例子，当用打孔卡来记录大学生的信息时，每张卡片上都需要输入学生的宿舍楼的名字，如果发现所输入信息的学生都在同一栋楼，就可以使用 029 型打孔机的自动重复功能来完成宿舍楼名称的填写。
+
+像这样的自动化操作可以通过打孔卡给 029 型打孔机编程控制。安装打孔卡的<ruby>圆柱形装置<rt>drum</rt></ruby>就在 U 形轨道中间部分的右上角。通过使用 029 型在打孔卡上写下程序，然后把打孔卡的装入圆柱形装置，再将其安装到打孔机内后，就完成了一次给 029 型打孔机的编程任务。用户可以通过这种方式对打孔卡的每一列都按需要定义不同的自动化操作。029 型打孔机允许指定某些列重复上一张打孔卡相同位置的字符，这就是它能更快的输入学生信息的理由。它还允许指定某些列只能输入数字或者字母，指定特定的列为空或者到某一列时就直接跳过一整张打孔卡。这样的可编程特性使它在输入拥有固定格式的数据时效率很高。密歇根大学制作的[进阶教学视频][5]包括了给 029 型打孔机编程的过程，如果你已经掌握了它的基础操作，就快去看看吧。
+
+这会儿，无论你是否看了密歇根大学制作的视频，都会感叹打孔机的操作之简便。虽然修正错误的过程很乏味，但除此之外，操作一台打孔机并不像想象的那样复杂。我甚至可以想象打孔卡之间的无缝切换让 COBOL 和 FORTRAN 程序员忘记了他们的程序是打在不同的打孔卡上而不是写在一个连续的文本文件内。另一方面，思考一下打孔机是如何影响编程语言的发展也是很有趣的，虽然它仅仅是一台输入设备。结构化编程最终会出现并鼓励程序员把整个代码块视为一个整体，但可以想象打孔卡程序员们强调每一行的作用且难以认同结构化编程的场景。同时你能够理解他们为什么不把代码块闭合所使用的括号放在单独的一行，只是因为这样会浪费打孔卡。
+
+现在，虽然没有人再使用打孔卡编程了，每个程序员都该试试[这个][6]，哪怕一次也好。或许你因此能够更好的理解 COBOL 和 FORTRAN 的历史，或许你就能体会到为什么每个人把 80 个字符作为长度限制的标注。
+
+喜欢吗？这里每两周都会发表一篇这样的文章。请在推特上关注我们 [@TwoBitHistory][7] 或者订阅我们的 [RSS][8]，这样你就能在第一时间收到新文章的通知。
+
+--------------------------------------------------------------------------------
+
+via: https://twobithistory.org/2018/06/23/ibm-029-card-punch.html
+
+作者：[Two-Bit History][a]
+选题：[lujun9972][b]
+译者：[wwhio](https://github.com/wwhio)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://twobithistory.org
+[b]: https://github.com/lujun9972
+[1]: https://twobithistory.org/images/ibm029_front.jpg
+[2]: https://twobithistory.org/images/card.png
+[3]: http://www.jkmscott.net/data/Punched%20card%20013.jpg
+[4]: https://www.youtube.com/watch?v=kaQmAybWn-w
+[5]: https://www.youtube.com/watch?v=SWD1PwNxpoU
+[6]: http://www.masswerk.at/keypunch/
+[7]: https://twitter.com/TwoBitHistory
+[8]: https://twobithistory.org/feed.xml