Control Flow - Control Structures in Practice

Control Structures in Practice

Most programming languages with control structures have an initial keyword which indicates the type of control structure involved. Languages then divide as to whether or not control structures have a final keyword.

  • No final keyword: Algol 60, C, C++, Haskell, Java, Pascal, Perl, PHP, PL/I, Python, PowerShell. Such languages need some way of grouping statements together:
    • Algol 60 and Pascal : begin ... end
    • C, C++, Java, Perl, PHP, and PowerShell: curly brackets { ... }
    • PL/1: DO ... END
    • Python: uses indentation level (see Off-side rule)
    • Haskell: either indentation level or curly brackets can be used, and they can be freely mixed
  • Final keyword: Ada, Algol 68, Modula-2, Fortran 77, Mythryl, Visual Basic. The forms of the final keyword vary:
    • Ada: final keyword is end + space + initial keyword e.g. if ... end if, loop ... end loop
    • Algol 68, Mythryl: initial keyword spelled backwards e.g. if ... fi, case ... esac
    • Fortran 77: final keyword is end + initial keyword e.g. IF ... ENDIF, DO ... ENDDO
    • Modula-2: same final keyword END for everything
    • Visual Basic: every control structure has its own keyword. If ... End If; For ... Next; Do ... Loop; While ... Wend

Read more about this topic:  Control Flow

Famous quotes containing the words control, structures and/or practice:

    “The inability to control our children’s behavior feels the same as not being able to control it in ourselves. And the fact is that primitive behavior in children does unleash primitive behavior in mothers. That’s what frightens mothers most. For young children, even when out of control, do not have the power to destroy their mothers, but mothers who are out of control feel that they may destroy their children.”
    —Elaine Heffner (20th century)

    “If there are people who feel that God wants them to change the structures of society, that is something between them and their God. We must serve him in whatever way we are called. I am called to help the individual; to love each poor person. Not to deal with institutions. I am in no position to judge.”
    —Mother Teresa (b. 1910)

    “Tricks and treachery are the practice of fools that have not wit enough to be honest.”
    —François, Duc De La Rochefoucauld (1613–1680)