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6/26/2011

Error control

Error control is a strategy used to catch situations that blocks a sucessful result of an application operation. This can be viewed in diferent levels of an application. At low level: one function could receive a unespected parameter. At high level, a tool could not accept a specific set of actions from the user.

6/25/2011

Unicode

If you work with Web programming, you might have used character encoding. At begining, computers have used ASCII, that provides basic symbols of English language and some special computer control characters. It was done using 1 byte per character, that could provide 256 characters. In practice, there were only 128 characters, because the first bit was not used.

When other countries starts to use computer, they needed to work with their own language, but ASCII did not provide all language symbols. To resolve that, it was created table maps that associates a symbol with a specific byte. One common charset was ISO-8859-1, that provides Latin symbols. Although, was created many different charsets, incompatible between them and was hard to make programs that suports many languages (many charsets).

To solve this new problem, the Unicode was created. This article shows what unicode is, what are its benefits and how to work with it.

6/14/2011

Scheduled Tasks

Information Systems often have tasks that should be done by schedule. This feature usually is needed because two reasons:

  1. because the task needs to be called at a specific moment;
  2. because the task is too long and it is impractible to take the user waiting while the task does not finish.

6/01/2011

PDO - PHP Data Objects

What is PDO?

PDO (PHP Data Objects) is a PHP module created in the Object Oriented Paradigm, and its goal is to provide a standarized way to PHP connect/comunicate to a Relational Database. It was created in PHP version 5. So, PDO is an interface that defines a set of classes and its method signatures to comunicate with a Database.

Each Database Management System (DBMS) can provide its own driver to PDO. Although PDO provide method signatures, some features can not be supported by some DBMS. So, calling this kind of method may be "useless", depending the driver was used or the DBMS model/version. For example, some engines of MySQL DBMS do not support transactions, so, the method "beginTransation" (that begin a new transation) simply take no effect at this condition.