CR, also known as Carriage Return is 0x0D in ASCII. It refers to the special character that moves the cursor to the beginning of the line. In some programming languages, we use "\r" to print it. This is elementary knowledge for any programmer.
But why is it called "carriage return"? What is a "carriage"? Where did it go, and why does it have to return? :-)
I was doing some research on old typewriters, when I realized that the name originates back to them. The carriage, was a mechanism that carried the paper.
By about 1910, the "manual" or "mechanical" typewriter had reached a somewhat standardized design. There were minor variations from one manufacturer to another, but most typewriters followed the concept that each key was attached to a typebar that had the corresponding letter molded, in reverse, into its striking head. When a key was struck briskly and firmly, the typebar hit a ribbon (usually made of inked fabric), making a printed mark on the paper wrapped around a cylindrical platen.
The platen was mounted on a carriage that moved left or right, automatically advancing the typing position horizontally after each character was typed. The paper, rolled around the typewriter's platen, was then advanced vertically by the "carriage return" lever (at the far left, or sometimes on the far right) into position for each new line of text. --source: wikipedia
As you might expect, this is also the origin of the "return key":
The first power carriage return was added to electric typewriters by Smith Corona in 1960. The key for this was usually labeled "carriage return" or "return". [...] To improve the keyboard for non-English-speakers, the symbol ↵ (U+21B5) was introduced to mark this key, since this graphic could communicate the action of the key without using words. --source: wikipedia
Had you asked me about the meaning of the return key on my keyboard a couple of days ago, I would have said that it returns the cursor to the beginning of the line. My perception as a computer user, is that the "cursor" moves on the screen (on the virtual paper) as I type. However, back in the typewriter days, the type bars typed only at a specific point, so the paper had to move to the left as we typed, and the "carriage return lever", or the "return key" actually moved the paper.
I find it very interesting how terms from an old technology like typewriters are still present in modern technology like computers and that even if their meaning has changed, there is still a reference to their original usage. (I also enjoyed reading this online typewriter manual, if you are like me, you will probably enjoy it too.)
[*] photo by James B Brooke