3 ms·

Just like semantic indentation, ":" is ABC's heritage. It was discovered that newbie programmers comprehend block operations better when they end with ":". ht

• nivertech 16y ago
  back in time, there was several schools for language syntax design for composite statements: 1. "Open" statements (Pascal): IF x THEN s1 ELSE s2; IF x THEN BEGIN s1; s2 END ELSE BEGIN s3; s4 END WHILE c DO s; WHILE c DO BEGIN s1; s2 END The problem with this design was need to use blocks (BEGIN ... END) and complex rules in case of nesting. 2. "Closed" statements (Algol 68) IF x THEN s1; s2 ELSE s3; s4 FI // END IF WHILE c DO s1; s2 OD // END WHILE You can see new kind of parenthesis IF-FI, DO-OD, etc. I more like "closed" syntax. But C syntax with it's brackets blocks "{...}" instead of "BEGIN...END" made this less an issue.