Variable parameter
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Variable parameter (or Reference Parameter) is input and output parameter meaning it can be used for passing a value to a function or a procedure as well as to get back a value from function or procedure. It indicated by the use of the keyword var in front of the formal parameter.
Variable parameter given a new nickname. The method refers to the same variable and changes made will affect the actual variable.
XOR swap
procedure XorSwap( var i,j:integer );
begin
i := i xor j ;
j := i xor j ;
i := i xor j ;
end;OrderSmallBig
procedure OrderSmallBig( var a,b:integer );
begin
if a > b then XorSwap( a, b );
end;