J K Scrolling

Gmail Labs keyboard shortcuts include an important set of keys to navigate between conversations: J and K, to navigate to older and newer conversations respectively. Keyboard shortcuts originated as a labs feature for Gmail but its youngest sibling Google+ has shortcuts, albeit very few, enabled by default: The first ones talked everywhere are J and K. This was expected, and shared and reshared through posts, where else but on Google+.

I was in for a surprise when I tried the same on Twitter. And Yammer. And realised they too use the J and K keys to scroll through messages. Google (search) tells me Tumblr also lets its users scroll up and down by pressing J and K; I could never catch up on Tumblr.

.			Yammer	Twitter	Google Plus	Gmail	Google Reader
.		Selected item pointer	Blue arrow	Blue background	Darker blue left border	Black arrow	Expands the post
.		Behaviour for new messages	Pointer shifts to top	Retains last position	Retains last position	Retains last position	Retains last position
.		Selection alignment	Center	Center	Top	None	Top
.	Sync with scrolling	Mouse	No	No	Yes	No	No
.		Arrow keys, Page Up/Dn	No	No	No	No	No
.		Home/End	No	No	Yes	No	No

The above table summarises J K Scrolling for the popular services that support it, and properties of the pointer and the this mode of scrolling in general. Facebook has a few useless shortcuts, but does not support J K. LinkedIn does not have keyboard shortcuts at all. Google Plus wins here as well, because it syncs your pointer to the currently selected message even if you scroll using your browser scrollbar, or navigate to the beginning of the stream using the Home key.

The use of J and K to scroll down or up can be dated back to 1976, when the vi editor was created, which also used the H and L keys to move left and right.

If you are wondering why were these keys chosen to scroll, the reason lies in the ADM-3A terminal, one of the first computer terminals, manufactured in 1975. The keyboard did not have a separate numpad in the right, but had multi-functional keys, and H, J, K, and L were aptly placed to be used as navigation keys.

The cost of one of these terminals 36 years ago was $1195! And had no processing/storage. Imagine what processing speeds and storage will that much money buy you today, even if you do not adjust for inflation.

*Images of the keyboard and the terminal are from Wikipedia from here and here, used under the Creative Commons Attribution-ShareAlike 3.0 License.