Stupid Question 148: Why the love for semicolons in so many programming languages?

There is a historic perspective to this as well - take C versus Basic, why does C use semi colons & Basic doesn't? because Basic is an older language and the common keyboards at that time didn't have an easily findable semicolon key.

This moves to current trends in design as well, like significant white space. Why wasn't that always used? Because the hardware of the day in rendering text could not do a good enough job. Now we have much better rendering, fonts and tooling which make significant white space a viable design choice where it wasn't in the past. 

That is a very good point! Apart from being used to using semicolons, I actually like using significant whitespace. 

Funny, I wondered about that a while ago and found this on StackOverflow: http://stackoverflow.com/questions/1308591/in-which-language-did-semicolon-first-appear-as-a-terminator
It's more of a where than a why however. 

In early days, BASIC was completely line-oriented (one statement to a line, each line numbered).  You couldn't even have an if-block -- The only thing an if could do was a goto.  Hence, end-of-line indicated end-of-statement.

COBOL was (is) based on English and English grammar, with each statement formatted like a sentence, hence it uses a period (aka full stop) to indicate end-of-statement.

Fortran, like Basic, is line-oriented, so end-of-line = end-of-statement.  Fortran also has some weird ideas about whitespace insignificance.  In a classic bug, it's noted that "DO 100  I = 1,10"  is a loop statement (roughly equal to FOR I = 1 to 10 in Basic), while "DO 100 I = 1. 10"  (that's the same line with a typo of a period instead of a comma") is actually an assignment statement (essentially creating a floating point variable named DO100I and assigning 1.10 to it)
  Formatting was quite strict.  The only thing allowed in column 1 was either a "C" (indicting the line was a comment) or a blank.   Column 2-7 were for jump labels.  Columns 8-72 were for the program statements. Column 73-80 were for a sequence number (in case you dropped the punch card deck).  Nothing beyond column 80, because that's how big a punch card was.

When C came around (or actually it's precursor), the idea was to rebel against the fixed formatting, and allow programmer to divide lines up how that felt.  Parsing that was much easier with an explicit end-of-statement character.  Since the period already had a purpose (member selection in structs), they had to look among the other characters on a standard keyboard. 

Modern parsing techniques can ONLY eliminate the need end-of-statement characters.  Javascript allows an "implied semi-colon" at the end-of-statement, but it's not perfect, and a missing semi-colon can lead to incorrect interpretation of the code. 

I think the best reason, besides historical tradition is that the semicolon key doesn't require that you press shift, doesn't conflict with any other kind of syntax and allows for writing multiple instructions on the same line. 

If I recall correctly, VaxBasic DID use semicolon line terminators. But that was a long, long time ago and I can't swear to it. 

The semicolon is easier to see than the full stop which was used as a terminator in Smalltalk. Remember also that a lot of early programming was done on teletypewriters - printers with keyboards - and the odd dot could vanish as the ribbon on the dotmatrix was worn. That device explains the behaviour of some of the early Unix text editors. 

Go back further than many of my younger colleagues have been alive, to the DOS days, in some common command shells, the semi-colon was used as a command separator when wanting to enter multiple commands on a line so the concept of semi-colon as the end of a command may have had help from there. 

Sorry, James, right idea, wrong columns... FORTRAN  column 1 - C = comment line; columns 2-5**   = line number (usually used only when required, but lovers of BASIC could number to their heart's content); column 6 nonblank = continuation of previous line (often just a 'C', some used single digits to count them); columns 7-72 text; columns 73-80 sequence numbers, optional, but useful when your deck had been dropped so that you could use a card sorter to put the deck back in order.    **=this varied according to system

Both FORTRAN and ALGOL were developed in the late 1950s. Note that the names indicated different orientations - FORTRAN is FORmula based; ALGOL is ALGOrithm based. For whatever reason - I'm sure Backus took it to his grave - the semicolon was selected in ALGOL to separate statements.  I'm sure he also took to his grave the reason behind the difference between the fixed-format FORTRAN and the free-format ALGOL. As a formula-based language, there would be only one formula per line. As an algorithm-based language, why not have more than one statement per line?  When I learned ALGOL60 back in the 1970s, none of my professors -- although they could explain much else -- could explain the romance of the semicolon:(