Internal Operations on LIMIT & OFFSET clause

Hi Friends,

I have one doubt in LIMIT & OFFSET clause operation.
I have a table "test_limit", and it contain,

SELECT * from test_limit;
s_no | name
------+-------------
1 | anbarasu
8 | egambaram
12 | jyothi
6 | mahalakshmi
4 | maheswari
2 | manju
5 | ramkumar
7 | sangeetha
11 | sasikala
10 | thekkamalai
9 | vivek
13 | ganeshwari
3 | anandhi
(13 rows)

Here, I applied LIMIT clause as bellow.
SELECT * from test_limit LIMIT 5;
s_no | name
------+-------------
1 | anbarasu
8 | egambaram
12 | jyothi
6 | mahalakshmi
4 | maheswari
(5 rows)

In this above query was processed only five records OR all the 13 record
was got and then only 5 record printed.
this is what my doubt.

I tried where clause in above query as bellow.
SELECT * from test_limit where s_no IN (1,2,3,4,5,6,7,8,9) LIMIT 5;
s_no | name
------+-------------
1 | anbarasu
8 | egambaram
6 | mahalakshmi
4 | maheswari
2 | manju
(5 rows)

In this case It should process up to records fulfill the requirement.
i.e atleast it should process 6 records.
My question is it is processed only 6 records (fulfill the requirement) or
all (13) the records.

I also tried ORDER BY clause as bellow.
SELECT * from test_limit ORDER BY s_no LIMIT 5;
s_no | name
------+-----------
1 | anbarasu
2 | manju
3 | anandhi
4 | maheswari
5 | ramkumar
(5 rows)

From this output, I know it is processed all(13) the records and the printed
only 5 records.
But, without ORDER BY clause I don't know how many record processing when
applying LIMIT clause.

---
Vanitha Jaya