The History of Caps Lock: Why Does the Caps Lock Key Exist?

One key caps lock.Benj Edwards

Caps Lock: The key that accidentally makes you scream when you press it. Do we really need it these days? Why is he even there, anyway? Let’s find out.

It all started in the days of the typewriter

Way back in ancient times, most typewriters only produces uppercase letters. In the 1870s typewriter maker Remington found an economical way to type upper and lower case letters. He did this by placing two symbols or letters (like upper case and lower case) on each character bar – the piece of metal that struck the letters on the paper.

To switch between the two symbols, you used a Shift key, which physically moved the entire character bar. This allowed a different part of the text bar to hit the ribbon and produce a different letter.

As the Shift key required relatively large mechanical force to be used, it could be tiring to keep it pressed continuously to type all caps. To solve this problem, Shift Lock was invented. It was basically a locking key that held the gear shift mechanism in place. It was often simply labeled “Lock”.

Shift Lock becomes Caps Lock

On typewriters, the Shift Lock has changed the function of each key, including letters (from lowercase to uppercase) and other characters (such as numbers to symbols).

In the computer age, however, keyboards no longer physically moved character bars, so keyboard locks were free to diversify. Some computer terminals and keyboards retained the Shift Lock key, while others included a new key called “Caps Lock”. This key only changed lowercase letters to uppercase and has no effect on other keys.

The Caps Lock key on an A DEC LA36 DECWriter II keyboard.The LA36 DECWriter II keyboard. DEC

According to this anti-Caps Lock item by Daniel Colin James, the original invention of Caps Lock appears to be related to this 1968 patent, which applies to an electronic terminal keyboard invented by Douglas A. Kerr of Bell Labs.

James interviewed Kerr, who said he invented the “Shift” key because his boss’s secretary was frustrated with entering strings like “@ # $%” instead of numbers when Shift Lock was on.

But patents don’t always translate into real products. The first record we could find of a caps lock key on a commercial product was the keyboard built into the LA36 DECwriter II terminal / teleprinter. Announced in 1974, it was a teletype and a computer printer at the same time.

The LA36 DECwriter II manual service describes caps lock (page 1-1) as a way to reduce the set of 96 uppercase and lowercase characters to a set of 64 uppercase characters. Originally, you could only adjust this internally via a switch on a printed circuit board. This suggests that the permanent production of capital letters was a desirable feature at the time. This could be because people were used to the all-caps style of many earlier teletypes.

There might, however, be an earlier example of caps lock that has yet to be rediscovered. It is not known to what extent DEC was influenced by Kerr’s patent (if it was). It is possible that the DEC caps lock was only created as a compatibility feature to mimic the uppercase behavior of older teletypes.

Caps Lock in the PC Age

Many of the early 1970s personal computers, such as the Apple II and TRS-80 Model 1, did not support lowercase letters, so there was no need to lock caps. However, IBM terminals, which have borrowed heavily from IBM Selectric Typewriter layout, often included a Shift Lock, and later, a Caps Lock key.

When IBM created its Personal computer in 1981 it included a caps lock key, but IBM positioned it just to the right of the space bar – relatively out of the way. To the left of the A key, you’ll find the Control key instead. This placement was common on all-caps terminals and TTY keyboards.

The IBM Model M.Benj Edwards

In 1984, when IBM converted its keyboard layout to 101-key extended keyboard (aka the M model), he placed the caps lock key to the left of A, and some people still angrily complain about that to this day.

Now that we know about Kerr’s patent and the DECWriter II, we can see that IBM has in fact just restored Caps Lock to its original position. Unfortunately, this position is important, so people often accidentally hit caps lock and type SHOUTY WORDS. It also disrupts the entry of case-sensitive passwords.

As we’ll see, however, there are actually some good reasons why the Caps Lock key is still around.

People still use caps lock

While many people complain about caps lock, others still use it in business to save time and effort. Some of the more common uses include:

Report headers: It’s a throwback to the era of the typewriter where different fonts were not available.
Serial numbers or VIN: Many of them only contain capital letters.
Legal agreements: Lawyers have used capital letters in legal documents since the typewriter era to make important terms more visible.
To Label Elements in Architectural Plans: Architects have been doing this since the days of handwritten letters. Today, they still use handwriting type architectural fonts in CAD programs.

Beyond these more publicized uses, there is also the issue of backward compatibility. For example, a feature that was present on IBM PC 5150 from 1981 is probably still there in case a legacy app is still using it.

How to type in caps without using caps lock

If you type in all caps frequently, but don’t like to use caps lock (or the key is missing), you’re in luck. Most word processing programs allow you to type text normally, select it, and then apply an all caps style. Here’s how to do it in a few common applications:

Microsoft Word: Select the desired text in uppercase, then press Ctrl + Shift + A on Windows or Command + Shift + A on Mac.
Google Docs: Highlight the text you want to edit, then select Format> Text> Uppercase> CAPITALS from the menu bar.
Pages: Highlight the text you want to change, then select Format> Font> Capitalization> All Caps from the menu bar.

You can also reassign caps lock key to perform another function (such as Control), use it as modifier key on Windows 10, or disable it completely.

While a lot of people never need it, caps lock isn’t wasted. As we noted above, many people still use it at work, so it will likely be with us for decades to come.

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