Does SQL Server put a shared lock on all tables within a transaction?

Would table1, table2 and table3 in code below, be locked with a shared lock from start of transaction to the end of transaction Or they would only be locked for the duration of their update, or insert statements and not for the entire transaction? Default isolation level is in effect in SQL Server.

begin tran
update table1 set column1 = 100
if @.ERROR = 0
begin
declare @.stat int
set @.stat = (select stat from table2 where employeeid = 10)
insert into table3 (col1, col2) values (@.stat , 325)
if @.@.ERROR = 0
commit tran
else
rollback tran
end
else
roll back tran

The answer to your first question is no. The answer to your second question is no.|||

Here's the long answer:

To keep this long answer from becoming a book, I'm going to classify IS/S locks as "shared", IU/I locks as "Update" and IX/X locks as "Exclusive". The I-versions are basically the same, but has a few differences, and usually used prior to obtaining the non-I version to eliminate lock starvation.

I'm going to assume table1 only has 1 row in it for this.

Update table1 ... will initially request an update lock as it scans the table for the rows to update, once it's located the correct rows, it will acquire an exclusive lock on those pages and rows then release the update locks.

set @.stat=(SELECT .. will request shared locks on the table, retrieve it's results, then release it's shared locks.

insert into table3 will acquire an exlusive lock on either an existing page, or a new page if either none are available, or the available ones are already exclusively locked. (There is an additional exclusive lock placed on the particular row as well).

The exclusive locks will be held until the transaction is either commited or rolled back. This stored procedure will not block any other session from either reading table2 at any time, or inserting a new record into table3. It will however block any other session from updating it's only row until the transaction is complete.