Technology Questions

Some of the rules which should be followed while naming a variable in VB are as follows: 

1) Characters should be less than 255.

2) Space between characters should be allowed.

3) A variable should begin with a number.

4) Period may not be permitted.

- %FOUND

 This is a Boolean variable which evaluates to TRUE if the last row is successfully fetched.

- %NOTFOUND

 This is a Boolean variable which evaluates to TRUE if the last row is not successfully fetched. This means there are no more rows to fetch.

- %ROWCOUNT

 Returns the number of rows fetched by the cursor.

- %ISOPEN

If the cursor is open, it evaluates to TRUE else FALSE.

The Singleton design pattern ensures a class only has one instance, and provides a global point of access to it. The class keeps track of its sole instance and ensures that no other instance can be created. Singleton classes are appropriate for situations where it makes sense for a single object to provide access to a global resource.Several Cocoa framework classes are singletons. They includeNSFileManager, NSWorkspace, NSApplication, and, in UIKit,UIApplication. A process is limited to one instance of these classes. When a client asks the class for an instance, it gets a shared instance, which is lazily created upon the first request.

Cloud data center doesn’t require experts to operate it, but it requires skilled people to see the maintenance, maintain the workloads and to keep the track of the traffic. The labor cost is 6% of the total cost to operate the cloud data center. Power distribution and cooling of the datacenter cost 20% of the total cost. Computing cost is at the end and is the highest as it is where lots of resources and installation has to be done. It costs the maximum left percentage.

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

A Thread is a block of code that can be executed in parallel with another block of code.

IUnknown as an interface of a COM object. Every COM object has to support IUnknown, besides optionally adding other interfaces.

IUnknown is made of QueryInterface, AddRef and Release.