When I run it,it appear error 88:'')'' is expected in A[L]:=sort;.
I think it is no need to add '')''.
What error 88 mean:?:

const
max = 100;
var
A: array[1..max] of real;
function Sort(L, R:integer):real;
begin
for L:= L to R-1 do begin
if A[L]<A[L+1] then begin
sort:=A[L+1];
A[L+1]:=A[L];
A[L]:=sort;
end;
end;
end;
var
I, N, L, R: integer;
{ Main Program }
begin
readln(N);
for I := 1 to N do
read(A[I]);
readln;
readln(L, R);
sort(L, R);
for I := 1 to N - 1 do
write(A[I]:0:7, ' ');
writeln(A[N]:0:7)
end.

I think the problem is that you try to assign to that real entity(a[L]) the result of the function. "sort" function has two parameters, so the correct assignment would be :

a[L] := sort(FirstParameter, SecondParameter); here you call the function.
I suggest to use a local variable of type real.

function Sort(L, R:integer):real;
var
Temp : real;
begin
for L:= L to R-1 do
if A[L]<A[L+1] then begin
Temp:=A[L+1];
A[L+1]:=A[L];
A[L]:=Temp;
end;
sort := 1; //another suggestion is to use a procedure instead of a function. A function is usefull when you have to return a value.
end;

First , error 88 is that the compiler waits for the (
and second I fixed your program.

program solution01;
const max = 100;
var A: array[1..max] of real;
function Sort(L, R:integer):real;
begin
for L:= L to R-1 do begin
if A[L]<A[L+1] then begin
sort:=A[L+1];
A[L+1]:=A[L];
sort:=A[L]; (*A[L]:=sort; wrong reference!Look at mine!*)
end;
end;
end; (*of Sort*)
var I, N, L, R: integer;
{ Main Program }
begin
readln(N);
for I := 1 to N do read(A[I]);
readln;
readln(L, R);
sort(L, R);
for I := 1 to N - 1 do write(A[I]:0:7, ' ');
writeln(A[N]:0:7);
end.
(*fixed by FlamingClaw.2010.04.13.Hungary*)

To Add to what FlamingClaw said
Your function needs to be refined still further. Understand the difference between a function and a procedure. You have not used the result of the function in the application but seem to have tried to use the result in the function itself.

procedure Sort(L, R:integer); //--> use procedure as no result is returned
Var Temp:Real;
aCount:Integer;
HasSwapped :Boolean;
begin
Repeat
HasSwapped:=False;
for aCount:= L to R-1 do
begin
if A[aCount]<A[aCount+1] then
begin
Temp:=A[aCount+1];
A[aCount+1]:=A[aCount];
A[aCount]:=Temp;
HasSwapped:=True;
end;
end;
Until HasSwapped=False;
(* Search for bubble sort for a more efficient sorting algorithm more suited to array sorting *)
end; (*of Sort*)