From Clomosy Docs

Returns an absolute value.
Abs returns the absolute value of the argument, X.
X is an integer-type or real-type expression.

Example

var
 i : Integer;

{
 i = -1235;
 ShowMessage('Before: '+ IntToStr(i));
 //The absolute value of i is taken and put back to i.
 i = Abs(i);
 ShowMessage('After: '+IntToStr(i));
}

Output:

See Also