Changes

of the embossed glyphs to be printed on the paper.  Typically, lowercase letters were converted to uppercase.  The paper was fed through the teletype via a friction feed similar to typewriters of the day.

of the embossed glyphs to be printed on the paper.  Typically, lowercase letters were converted to uppercase.  The paper was fed through the teletype via a friction feed similar to typewriters of the day.

The next advance in printing terminals used a different type of print-head called a dot-matrix printer.  The advantage is that these print heads could print faster than the entirely mechanical teletype print heads.  The original dot-matrix terminals could operate as fast as 300 baud (about 30 characters per second), but later advancements provided speeds up to 1200 baud (about 120 characters per second).  Dot-matrix printer technology consists of narrow metal pins organized in rows and columns (typically 7x9).  For a given glyph, a pattern of the pins were pushed out, through an ink ribbon, creating a representation of the glyph on the paper.  The paper was typically fed via a tractor mechanism: equally-spaced holes on the left and right margins of the paper were used by a mechanism to pull paper past the print line.   

The next advance in printing terminals used a different type of print-head called a dot-matrix printer.  The advantage is that these print heads could print faster than the teletype print heads.  The original dot-matrix terminals could operate as fast as 300 baud (about 30 characters per second), but later advancements provided speeds up to 1200 baud (about 120 characters per second).  Dot-matrix printer technology consists of narrow metal pins organized in rows and columns (typically 7x9).  For a given glyph, a pattern of the pins were pushed out, through an ink ribbon, creating a representation of the glyph on the paper.  The paper was typically fed via a tractor mechanism: equally-spaced holes on the left and right margins of the paper were used by a mechanism to pull paper past the print line.   

The first video terminals were nothing more than "glass teletypes".  That is, they simply replaced the paper with a video screen.  They often had the same restrictions as teletypes including uppercase only display.  However, free of mechanical constraints, they could operate at higher speeds than teletypes.  Obviously, there was no paper record of the output and so these devices were not appropriate for all applications.  Video terminals typically provided a 24 line by 80 column screen.  Each column position on each line is called a '''character cell''', which meant that each character took the same space on the screen, as opposed to proportional spacing. In place of a print head, a cursor was provided to indicate the location where the next output would show.  Cursors typically were inverse blocks or underscores, blinking or solid.  Each character was represented by a dot matrix (called a raster font) similar to dot-matrix print heads.

The first video terminals were nothing more than "glass teletypes".  That is, they simply replaced the paper with a video screen.  They often had the same restrictions as teletypes including uppercase only display.  However, free of mechanical constraints, they could operate at higher speeds than teletypes.  Obviously, there was no paper record of the output and so these devices were not appropriate for all applications.  Video terminals typically provided a 24 line by 80 column screen.  Each column position on each line is called a '''character cell''', which meant that each character took the same space on the screen, as opposed to proportional spacing. In place of a print head, a cursor was provided to indicate the location where the next output would show.  Cursors typically were inverse blocks or underscores, blinking or solid.  Each character was represented by a dot matrix (called a raster font) similar to dot-matrix print heads.