History Characters per line

the ruler on carriage of olivetti lettera 22. typewriter can print 87 characters in line

the limit of line length in 70–80 characters may originated various technical limitations of various equipment. american teletypewriters type 72 cpl, while british ones less, 70 cpl. in era of typewriters, designs of typewriter carriage limited 80–90 cpl. widespread , standard paper size in (8.5×11 ) has been imposing limitations on line length: possible print 85 or 102 characters (with font size either 10 or 12 characters per inch) without margins on typewriter. various margins (usually 1 1.5 inches each side, there no strict standard) these numbers may shrink 55–78 cpl.

a fortran coding form (paper). source code has 72 cpl, form 80-characters wide. last 8 positions identification sequence

in computer technology, line of ibm punched card consist of 80 characters. widespread computer terminals such ibm 3270 followed limitation, monitors show 80 cpl (but various number of lines), though terminals number either reduced half 40 cpl, limited 64 cpl (swtp ct-64, 16 lines), or optionally increased 132 cpl (dec vt100 family, 14 lines). such line lengths have been carried on text modes of personal computers.

the long line of 132 cpl comes line printers of mainframes.