CSS (Cascading Style Sheet)

Cascading Style Sheet is a technique that determines the presentation of web pages like layout, colour schemes, fonts, etc. Style information using certain set of formatting rules is provided in *.css file or style sheet. Using this technique, multiple web pages of a web-site having same display layout and formatting can be linked to a style sheet. Thus this technique provides easy and less time consuming way to web developers to create and change layout and/or format of multiple pages.

Client (Computer)

Client is referred to computer or software application that relies, to provide service, on another computer called Server installed in a network. Through a network, clients communicate with server and access, in common through following certain protocols, some or all of resources installed in network and on server.

Logic gates & their Truth Table

     Logic gates are digital circuits that do processing of digital circuits. Gates have one or more inputs but only one output. There are three basic logic gates and they are named as OR gate, AND gate & NOT gate. These three gates can be combined in various ways to perform more complex arithmetic functions based on processed input digital signals.

     There are two types of gates named as sequential gates and combinational gates. One type of logic gates called sequential gates, which have memory function, can process sequence of input digital values and outputs are based on sequences of applied inputs. Example of sequential gates are Flip-flops, Counters & Registers. Another types of logic gates called combinational gates, which do not have memory function, can process only instantaneous digital inputs and outputs are based on inputs applied at the moment of time. Examples of combinational gates are OR gate, AND gate, NOT gate, XOR gate, NAND gate, etc.

     Different types of logic gates which will be discussed here are ;

1. OR gate,
2. AND gate,
3. NOT gate,
4. NOR gate,
5. NAND gate,
6. EXCLUSIVE OR gate, &
7. EXCLUSIVE NOR gate.

OR gate

     This gate can have two or more than two inputs but only one output. OR gate is named so because output signal will be high if any of the input signals are high. Truth table and symbol of OR gate with two inputs are given below ;

OR gate & Its Truth Table

Output of OR gate is "X = A + B".

AND gate

     This gate can have two or more than two inputs but only one output. AND gate shows output only when all the inputs are applied at same time. Truth table and symbol of AND gate with two inputs are given below ;

AND gate & its Truth Table

Output of AND gate is "X = A . B".

NOT gate

     This gate has only one input and one output. NOT gate always gives output opposite to that of input signal i.e., if input signal is 0 then output will be one and vice versa. Truth table and symbol of NOT gate are given below ;

NOT gate & Its Truth Table

Output of NOT gate is "X = Ā".

NOR gate

     This gate can have two or more than two inputs but only one output. NOR gate is a combination of OR gate and NOT gate. NOT gate is connected to the output of OR gate. So the output of NOR gate is always opposite to that of OR gate. Truth table and symbol of NOR gate with two inputs are given below ;

NOR gate & Its Truth Table

NAND gate

      This gate can have two or more than two inputs but only one output. NAND gate is a combination of AND gate and NOT gate. NOT gate is connected to the output of AND gate like NOR gate. So the output of NAND gate is always opposite to that of AND gate. Truth table and symbol of NAND gate with two inputs are given below ;

NAND gate & Its Truth Table

EXCLUSIVE OR (XOR) gate ;

Ex-OR gate & Its Truth Table

EXCLUSIVE NOR gate

Exclusive NOR gate & Its Truth Table

Few other posts seeking your attention are ;

1. Rectifiers Theory @ Industrial Items

2. Hooke's Law @ All Laws of Science & Imporant Formulas

Cloud Computing

Now these days, we get a term to listen very frequently in news papers, TV channels, etc., which is  "Cloud Computing". Now couple of questions arise that what is this Cloud Computing & why everybody is discussing it ?

  

Let’s understand term Cloud Computing

To understand the concept of "Cloud Computing", let us first understand the meaning of cloud in the term "Cloud Computing". Cloud may be referred to as a data center or simply a huge data storage facility, which is well equipped with hardware & software to continuously serve the needs of the users & companies, owned by third party somewhere on the web. Companies store their data on the cloud and their customers or users  can access data stored by the company free of cost or on the basis of pay-per-use and this is called Cloud Computing. The data stored on the cloud can be any application software or information pertaining to some product, company, service, etc. One of the biggest and oldest examples of cloud computing is E-mail provided by Yahoo Mail or Gmail. Google Apps is another example of cloud computing, where users can access various applications free of cost like document viewers, translator, calender, Blogger, Picassa, etc.

          In general, cloud computing is delivering information, application software & other web based services for use by a company to users while hosting them on a cloud rather than investing in their small servers, which in general are expensive, not flexible to accommodate ever increasing future data storage requirements & prone to obsolete as technology is changing every second.

Pay per use – A feature of Cloud Computing

Now, to understand the concept of " pay per use ", the term used above, we can take an example of a small shop keeper, who needs a Tally software or any text editing software for only two or three times in a month not more than half hour or an hour, he would then use, on demand, the required software online simply on his browser using cloud computing and would pay a minimal amount as per usage rather than buying costly software. So one of the important characteristic of cloud computing is on demand usage of data, software, hardware or storage space.

Cloud may be public or private. A public cloud is one which is available for all. Anybody, who wish to use such cloud can pay as per usage to use cloud. Or simply, a cloud owned by a third party is generally a public cloud. Whereas private cloud is available for only one or a limited number of users or customers.

  

Benefits & Limitations of Cloud Computing

So, a question arises here that " why cloud computing ? ". Cloud computing will change future of IT because of its following benefits ;

1.     More Green Technolgoy ; Cloud computing is more green technology because having a number of small capacity servers create more electronic waste and more electricity in running servers & for their air-conditioning is required. So switching to cloud rather than investing in a number of small capacity servers is more environment friendly. Big companies may have large capacity servers by considering their future data storage space requirements but it also produces more electronic waste & consumes more electricity than cloud computing and at the same it is wastage of resources as such large capacity servers may not be used to their full capacity. So, the intent of cloud computing is not just using cloud but utilize the cloud in its full capacity, which specifically makes it more Green Technology.

2.     More Cost Effective ; Investing in costly hardware & software is not required with cloud computing. As I have already discussed above that we can use resources, whether it is hardware or software, on the basis of pay-per-use, so that the capital investment cost is almost zero. In conventional or earlier IT technology, where we maintain servers locally, also require administration staff, which makes it costlier. But in case of switching to cloud owned by third party or service provider, they them-self manage the administration of cloud. Again, if people invest in software, it is required to upgrade very frequently with its latest version. For example, document files created by using MS-Office 2007 is not compatible with its earlier versions. Cloud computing may be the solution of this problem, for example, we may read doc files using google docs free of cost and may prepare reply using existing version of MS-Office with upgrading the same.

3.     Flexibility ; It is generally difficult to handle ever increasing requirements of data storage space, costly hardware & costly software. Cloud computing is flexible enough to accommodate these requirements. As "on demand usage" is the characteristic of cloud computing, we may increase or decrease the usage of resources as per our requirements.

4.   Requirement of High band-width ; Improvements in technology like IT products and especially internet connectivity is the main factor, which is making companies to shift to cloud computing & making it a future technology. Therefore, one important thing to consider is if the internet connectivity is poor or internet connection, which we use for consuming services based on cloud computing, is slow then it can be a worst experience using cloud computing.

Few other posts seeking your attention are ;

BEE Energy Label & its Significance