Month: August 2014

stocks investment

1. Options Basics: Puts And Calls

 http://www.forbes.com/2006/08/23/investools-options-ge-in_wh_0823investools_inl.html

Options are divided into two categories: calls and puts. Calls increase in value when the underlying security is going up, and they decrease in value when the underlying security declines in price. Puts increase in value when the underlying security is going down and decrease in value when it is going up. So depending on what you anticipate happening in the market, you can buy a call or a put and profit from that movement.

To understand why the value of calls and puts fluctuate when the market moves up and down, you need to understand what each type of option gives you the right to do once you have purchased it.   

Call Options

A call option gives you the right to buy a stock from the investor who sold you the call option at a specific price on or before a specified date. For instance, if you bought a 35 October call option on General Electric , the option would come with terms telling you that you could buy the stock for $35 (the strike price) any time before the third Friday in October (the expiration date). What this means is, if GE rises anywhere above $35 before the third Friday in October, you can buy the stock for less than its market value. Or if you don’t want to buy the stock yourself or exercise the option, you can sell your option to someone else for a profit.

The drawback is if GE never rises above $35, your option won’t be worth anything because nobody wants to buy an option that allows them to buy a stock for a higher price than they could get it for if they just went out into the open market and bought it.

Put Options

A put option gives you the right to sell a stock to the investor who sold you the put option at a specific price, on or before a specified date. For instance, if you bought a 25 October put option on Pfizer , the option would come with terms telling you that you could sell the stock for $25 (the strike price) any time before the third Friday in October (the expiration date). What this means is, if Pfizer falls anywhere below $25 before the third Friday in October, you can sell the stock for more than its market value. And if you don’t want to sell the stock yourself, you can sell your option to someone else for a profit.

Now, you have to keep in mind that to make money you will not have purchased a put option on a stock that you own (although this can be a legitimate hedging strategy). If you owned the stock, the gains you would make on the put option would be offset by the losses you would incur on the stock. Instead, you would buy a put on a stock you don’t own and then buy that stock right before you are ready to exercise the put. For instance, if you have purchased a put on Pfizer with a strike price of $25, and the stock dropped to $20, you could go out into the open market, buy the stock for $20 and turn around and sell it for $25, making a $5 profit.

The tricky part about options is that they expire. If you don’t sell or exercise your option before the expiration date, you will lose your entire investment. That’s a scary proposition, so you need to take care to always watch your expiration dates.

Options are no longer just for large institutional investors. You too can take advantage of the flexibility and leverage these wonderful trading tools offer.

 

2. http://www.mitbbs.com/article_t2/Stock/35727611.html 

Advertisements

Stateful vs Stateless web server design

http://orca.st.usm.edu/~seyfarth/network_pgm/net-6-3-3.html

  • A stateful server remembers client data (state) from one request to the next.
  • A stateless server keeps no state information
  • Using a stateless file server, the client must
    specify complete file names in each request
    specify location for reading or writing
    re-authenticate for each request
  • Using a stateful file server, the client can send less data with each request
  • A stateful server is simpler
  • On the other hand a stateless server is more robust
    lost connections can’t leave a file in an invalid state
    rebooting the server does not lose state information
    rebooting the client does not confuse a stateless server

 

https://sites.google.com/site/assignmentssolved/mca/semester5/mc0085/11

Stateful Versus Stateless Servers

The file servers that implement a distributed file service can be stateless or Stateful. Stateless file servers do not store any session state. This means that every client request is treated independently, and not as a part of a new or existing session. Stateful servers, on the other hand, do store session state. They may, therefore, keep track of which clients have opened which files, current read and write pointers for files, which files have been locked by which clients, etc.

The main advantage of stateless servers is that they can easily recover from failure. Because there is no state that must be restored, a failed server can simply restart after a crash and immediately provide services to clients as though nothing happened. Furthermore, if clients crash the server is not stuck with abandoned opened or locked files. Another benefit is that the server implementation remains simple because it does not have to implement the state accounting associated with opening, closing, and locking of files.

The main advantage of Stateful servers, on the other hand, is that they can provide better performance for clients. Because clients do not have to provide full file information every time they perform an operation, the size of messages to and from the server can be significantly decreased. Likewise the server can make use of knowledge of access patterns to perform read-ahead and do other optimizations. Stateful servers can also offer clients extra services such as file locking, and remember read and write positions.

 

Another good website to read:

http://www.cs.jhu.edu/~yairamir/cs418/os10/tsld018.htm