views:

1980

answers:

9

or "How I learned to stop worrying and learned to love measurement systems"

I wanted a central spot that I can refer to later to give me a quick low-down on various units of measurement used in programming. SO seemed the best place to put it, and while I could go ahead and answer the question myself, y'all are a much smarter bunch than I, so I might as well let you do it.

Please pick one unit that you're familiar with, use "#name" in the first line to give it as the heading (making it easy to find) and define it within your answer. Please do not duplicate - add comments or edit existing answers rather than adding a new answer. Similar units are still seperate - so please don't define em and en in the same answer. If a unit is exactly the same as another unit, add a line for "aliases" below the heading.

If it's a particularly obscure measurement type, please link to a second reference so people don't downvote you because they've never heard of it.

I'm seeing a lot of downvoting - I suppose people believe this doesn't add value to StackOverflow's community. Please consider commenting below if you feel this doesn't add to the community, or if you think this is a bad question. I'm interested in improving it if you have any suggestions.

The great thing about standards is there are so many to choose from!

+1  A: 

PostScript Point

1/72th of an inch.

Coincoin
Of course, that puts you at odds with Euclid...
Ed Swangren
...as well as Wikipedia apparently. I guess we are not talking the Geometric point :)
Ed Swangren
And the Point can be 1/72 or 1/72.27 of an inch, depending on which definition you are using. There may be other definitions too, but these are the two I'm familiar with.
Eddie
+3  A: 

Pica

A typographical measure of 12 points, sometimes (incorrectly) called an Em. (in fact, an em is actually a horizontal distance the same as the point size of the type).

ConcernedOfTunbridgeWells
+2  A: 

Twips

'Twentieth of an Imperial Point'. A measure used for marking up positions of widgets in Visual BASIC user interfaces. It was used this way so that positions could be specified precisely using integers. One Twip = 1/20 point = 1/1440 inch.

ConcernedOfTunbridgeWells
+4  A: 

Pixel

One of the little colored squares on your screen.

Adam Jaskiewicz
Should be community wiki
John Sheehan
... coming from a man who's answer to 'Hidden Features of ASP.Net' is http://stackoverflow.com/questions/54929/hidden-features-of-asp-net/177078#177078 - and (along with several several other answers of his to the same question) is *NOT* community wiki.
ConcernedOfTunbridgeWells
Should NOT be community wiki, unless the individual wishes it to be. Vote one whether it adds to SO or not, but not on meta aspects of the question or answer.
Adam Davis
+2  A: 

DPI

Dots per inch. A dimensionless number used to measure the resolution of something in space, i.e. with respect to real occupied physical size.

dds complexity and headache since the standard/default DPI of a computer screen varies with the operating system. Macintosh screens generally have 72 DPI, while Windows favors 96. If you don't compensate for this when displaying images (and text), you will get unexpected variations.

Always amusing when people start talking of "the DPI of this image", for digital images such as PNG or JPEG. To me, they only have absolute pixels in them, unconnected to any physical size. If you want to print the image on a (for instance) 300 DPI printer, then you need to adapt and scale to get it correct, but the image itself only has pixels.

unwind
+1  A: 

I recommend to ammend the above answers using the following descriptions

PICA

Pica Typographic unit of measurement in the anglo-american point system. One pica is 1/72 Inch (0,351 mm) and equals 12 pica points. The didot equivalent of a pica is a cicero. A standard unit of measure in newspapers. There are 6 picas in one inch, 12 points in one pica.

PICA POINT

Pica Point 1/12 of a pica

POINT

996 points are equivalent to 35 centimeters, or one point is equal to .01383 inches. This means about 72.3 points to the inch. We in electronic printing use 72 points per inch

1 point (Truchet) = 0.188 mm (obsolete today)

1 point (Didot) = 0.376 mm = 1/72 of a French royal inch (27.07 mm)

1 point (ATA) = 0.3514598 mm = 0.013837 inch

1 point (TeX) = 0.3514598035 mm = 1/72.27 inch

1 point (Postscript) = 0.3527777778 mm = 1/72 inch

1 point (l’Imprimerie nationale, IN) = 0.4 mm

EM

An old printing term for a square-shaped blank space that’s as wide as the type is high; in other words, a 10-point em space will be 10 points wide.

EN

Half an em space; a 10-point en space will be 5 points wide.

DPI

The number of dots per inch a printer prints. The higher the dpi, the finer the resolution of the output.

PIXEL

The smallest dot you can draw on a computer screen

CPI

Counts per inch for Mouse properties and The number of horizontal characters that will fit in one inch for Printer properties

PITCH Alias CPI

Pitch describes the width of a character. Pitch equals the number of characters that can fit side-by-side in 1 inch; for example, 10 pitch equals 10 characters-per-inch or 10 CPI. Pitch is a term generally used with non-proportional (fixed-width) fonts.

TWIPS

A twip (derived from TWentieth of an Imperial Point) is a typographical measurement, defined as 1/20 of a typographical point. One twip is 1/1440 inch or 17.639 µm when derived from the PostScript point at 72 to the inch, and 1/1445.4 inch or 17.573 µm based on the printer's point at 72.27 to the inch

Additional Units:

LPI

The number of vertical lines of text that will fit in one inch

PPI

Thickness of paper, expressed in thousandths of an inch or pages per inch. or sometimes no of horizontal pixels closely printed or displayed per inch.

FONT SIZE

Font size or Type size is the baseline distance for which the font was designed. A font should normally be identified and selected by this size, because the intended baseline distance is much more relevant for practical layout work than the actual dimensions of certain characters.

FONT HEIGHT

Font height is the height in mm of letters such as k or H. Typically, the font height is around 72% of the font size, but this is of course at the discretion of the font designer.

X-HEIGHT

x-height indicate typesize of lower-case letters excluding ascenders and descenders (from the height of the lower-case x)

H-HEIGHT

h-height or cap height refers to the height of a capital letter above the baseline for a particular typeface. It specifically refers to the height of capital letters that are flat—such as H or I—as opposed to round letters such as O.

lakshmanaraj
This is nice, but would you mind breaking them up into individual answers, and instead of duplicating existing answers add comments below them for additional information?
Adam Davis
Since I am busy with other work, I will do tomorrow.
lakshmanaraj
Is it tomorrow yet? ;)
mizipzor
@mizipzor If you have time, please do it.
lakshmanaraj
+3  A: 

EM

An old printing term for a square-shaped blank space that’s as wide as the type is high; in other words, a 10-point em space will be 10 points wide.

lakshmanaraj
+2  A: 

EN

Half an em space; a 10-point en space will be 5 points wide.

lakshmanaraj
+2  A: 

CPI

Counts per inch for Mouse properties and

The number of horizontal characters that will fit in one inch for Printer properties

PITCH Alias CPI

Pitch describes the width of a character. Pitch equals the number of characters that can fit side-by-side in 1 inch; for example, 10 pitch equals 10 characters-per-inch or 10 CPI. Pitch is a term generally used with non-proportional (fixed-width) fonts.

lakshmanaraj