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
- Algol 60 and Pascal :
- 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
ENDfor everything - Visual Basic: every control structure has its own keyword.
If...End If;For...Next;Do...Loop;While...Wend
- Ada: final keyword is
Read more about this topic: Control Flow
Famous quotes containing the words control, structures and/or practice:
“Not being able to control events, I control myself; and I adapt myself to them, if they do not adapt themselves to me.”
—Michel de Montaigne (1533–1592)
“It is clear that all verbal structures with meaning are verbal imitations of that elusive psychological and physiological process known as thought, a process stumbling through emotional entanglements, sudden irrational convictions, involuntary gleams of insight, rationalized prejudices, and blocks of panic and inertia, finally to reach a completely incommunicable intuition.”
—Northrop Frye (b. 1912)
“In my practice I’ve seen how people have allowed their humanity to drain away. Only it happens slowly instead of all at once. I didn’t seem to mind.... All of us, a little bit. We harden our hearts. Grow callous. Only when we have to fight to stay human do we realize how precious it is to us, how dear.”
—Daniel Mainwaring (1902–1977)