A friend asked, "Why we need to use a space after a period or comma?"  Here's my answer.
     The punctuation (comma, period, question mark, etc. indicates a pause in a spoken sentence.  When I was in elementary school we were taught to add two spaces after a period and one space after a question mark.

     Actually, it gets more complicated than that.  Please let me explain.  The reason two spaces are used after a period is that it makes the "full stop" or the "end of the sentence" emphasized and easy to see.  If you are reading fast, it makes reading easier.  With the advent (introduction or creation) of computers, many people have gone to using one space after a period.  This is especially true for scientific journals (magazines that publish articles related to science).  Journals have done many things to "save space" including using one space after a period.  This allows them to publish more articles because they can cram (pack tightly) more information into less space.  For example, in lists of references, they now will write PE Hyatt and not Philip E. Hyatt for someone's name.  I do many other things as an editor to save space.  Comparisons are at the end of this blog.

     Remember that I learned to type on a typewriter, not a computer.  If we made a mistake, we had to pick up an eraser and erase the mistake on our papers.  So, when we put in two spaces, we had to hit the space bar twice.  If we wanted to "hit the tab key" we actually moved a metal tab on the back of the machine to "set the tab."  Then, when we hit the tab key, the "carriage" (a moving part) moved to the tab location.  If we typed, the carriage moved the paper one space to get ready to hit the paper.  If you typed too fast, the keys that hit the paper to make the letters would hit each other and get jammed up.  You had to get ink on your fingers to pull them apart.

     That said, punctuation has a role.  For example, try to read the rest of this paragraph.Thisparagraphnowhasnospacing.AncientChinesewaswrittenlikethis,alljammedtogether.

     As you can see, that is very hard to read.If you don't use spaces at natural pauses,then your writing gets harder to read.I'm using this paragraph as an example.To an American this looks very childish.  So, here's some rules.

Rules

Period - . - use two spaces if you want to look professional, one for informal writing .Never put the space before the period as in this example.

Comma - , - use one space after a comma

Opening parenthesis - ( - use one space (like this) when opening a parenthetical statement (something in parenthesis)because(this is too crowded).

Question mark - ? - one space after

Exclamation point - ! - one space after

Just look in magazines for spacing with @, #, $, %, etc.

Space saving methods.

Longer:

The results are listed in Table 1.

The results were defined by the original authors.

Shorter:

Table 1 lists the results.

The original authors defined the results.

Enjoy!