Statement block

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In computer programming, a statement block (or code block) is a section of code which is grouped together, much like a paragraph; such blocks consist of one, or more, statements. Statement blocks help make code more readable by breaking up programs into logical work units.

In C, C++, Java and some other languages, statement blocks are enclosed by curly braces {}. In Ada, Pascal, and some other languages, blocks are denoted by "begin" and "end" statements. In Python they are indicated by indentation (the Off-side rule). Unlike paragraphs, statement blocks can be nested; that is, with one block inside another. Blocks often define the scope of the identifiers used within.

Blocks often have subtle but important differences in semantics. In languages in the C tradition, they define identifier scope. In C++ they can be used to define object lifetime (creation and destruction). In some languages (such as Pico) they are merely used for grouping expressions without notions of variable scope. In languages such as Smalltalk, blocks are objects in their own right, extended with a reference to their environment of definition, i.e. closures.

Contents

[edit] A typical statement block

int main()
{
  return 0;
}

[edit] A nested statement block

int main()
{
  int x = 1;
 
  if (x == 1)
  {
     x++;
  }
  return 0;
}

[edit] Other formats

Java programmers typically use a slightly different convention for placing the braces. The opening brace is on the same line as the method declaration:

int main() {
  return 0;
}
 
int main() {
 
  int x=1;
 
  if (x == 1) {
     x++;
  }
 
  return 0;
}

Visual Basic requires an explicit End statement, as follows:

If x > 0 Then
 
  y = y + x
 
End If
 
For i = 1 To 10
 
  DoSomething(i)
 
Next ' or Next i

SQL Server and some other languages (e.g. Pascal) use Begin ... End blocks

IF y IS NOT NULL
BEGIN
  SELECT * FROM employee WHERE name = y
END

[edit] See also

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