Stock exchange points

Every stock exchange has an index number based on the average of the share prices. For example an index for the UK Stock Exchange is the FTSE 100, which is an index number based on the average of the top 100 share prices. It started in 1984 with a base of 1,000 and has now grown to around 7,000. Different stock exchanges has different starting points and a different starting base, and so the points they change by cannot be compared with each other. More important is the % change from day to day. So if the index goes from 10,000 to 11,000, it means that on average share prices have increased by 1,000/10,000 = 10%

So every country has difference in starting base? Amd whats basically the starting base?

Yes - they all have different starting points (and usually every so often they start again). The starting base is up to the individual countries. For the FTSE index the start was 1,000, but other countries might choose 100 or 10,000.

and sir what if a country sells a stake of a stock exchange, and they say that its currently owned by like 500 brokers, who might look to sell 40 percent stake ? thanks alot btw

That has nothing to do with it, unless they decide to redefine the index used. The stock exchange is simply a market like any market - like a market selling food for example. Who actually owns the market is not relevant (and it is not the brokers who own it - they just rent space from the owners, just as traders in any market rent space from the owners of the market).