Unit Converter Php Source Code: A Simple and Lightweight Library for Converting Units

While Kelvin is the SI Unit of temperature, people generally prefer Fahrenheit or Celsius unit type to measure temperature. We're going to build a temperature converter that will convert Fahrenheit, Celsius, and Kelvin units to each other, using the most popular CSS framework called Bootstrap 4.6 and JavaScript library - jQuery.

Unit Converter Php Source Code

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In this tutorial, we will create a temperature converter and walk through how the website works. We will deploy this project on GitHub using GitHub pages, a hosting service by GitHub that allows you to publish static websites online directly from repositories. The tutorial will guide you through the step-by-step process of setting up the GitHub repositories before publishing the website. The suggested text editor is VScode, but you can choose any other text editor you like.

The purpose of the application we are going to create is to perform unit conversions from Fahrenheit to Centigrade. Obviously the first step is to create a new Xcode project to contain our application. Start Xcode and on the Welcome screen select Create a new Xcode project. On the template screen choose the Application option located under iOS in the left hand panel and select View-based Application. Click Next, name the product UnitConverter, enter your company identifier and make sure that the Product menu is set to iPhone. On the final screen, choose a location in which to store the project files and click on Create to proceed to the main Xcode project window.if(typeof ez_ad_units!='undefined')ez_ad_units.push([[160,600],'techotopia_com-box-1','ezslot_3',130,'0','0']);__ez_fad_position('div-gpt-ad-techotopia_com-box-1-0');report this adCreating the User InterfaceBefore we begin developing the logic for our interactive application we are going to start by designing the user interface. When we created the new project, Xcode generated an Interface Builder NIB file for us and named it UnitConverterViewController.xib. It is within this file that we will create our user interface, so select this file from the project navigator in the left hand panel to load it into Interface Builder. Once Interface Builder has loaded the file select the far right of the three View buttons in the Xcode toolbar to display the right hand panel. In the lower panel, select the Show the Object library toolbar button (the black 3D cube) to display the UI components. Alternatively, simply select the View -> Utilities -> Object Library menu option:From the Object Library panel (View -> Utilities -> Object Library'), drag a Text Field object onto the View design area. Resize the object and position it so that it appears as follows:Within the Attribute Inspector panel (View -> Utilities -> Attribute Inspector), type the words Enter temperature into the Placeholder text field. This text will then appear in a light gray color in the text field as a visual cue to the user.Now that we have created the text field for the user to enter the temperature into, the next step is to add a Button object that can be pressed to initiate the conversion. To achieve this drag and drop a Rounded Rect Button object from the Library to the View. Double click the button object so that it changes to text edit mode and type the word Convert onto the button. Finally, select the button and drag it beneath the text field until the blue dotted line appears indicating it is centered vertically in relation to the text field before releasing the mouse button.The last user interface object we need to add is a label where the result of the conversion will be displayed. Add this by dragging a Label object from the Library window to the View and position it beneath the button. Stretch the width of the label so that it is approximately a third of the overall width of the view and reposition it using the blue guidelines to ensure it is centered in relation to the button.

When the user enters a temperature value into the text field and touches the convert button we need to trigger an action that will perform a calculation to convert the temperature. The result of that calculation will then be presented to the user on the label object. The Action will be in the form of a method that we will declare and implement in our View Controller class. Access to the text field and label objects from the view controller method will be implemented through the use of Outlets.Before we begin, now is a good time to highlight an example of the use of subclassing as previously described in An Overview of the iPhone iOS 4 Application Development Architecture. The UIKit framework contains a class called UIViewController that provides the basic foundation for adding view controllers to an application. In order to create a functional application, however, we inevitably need to add functionality specific to our application to this generic view controller class. This is achieved by subclassing the UIViewController class and extending it with the additional functionality we need.When we created our new project, Xcode anticipated our needs and automatically created a subclass of UIViewController and named it UnitConverterViewController (using as a prefix the name that we gave to our new project). In so doing, Xcode also created two source files; a header file named UnitConverterViewController.h and a source code file named UnitConverterViewController.m.

From within the Xcode project window click on Run to compile the application and run it in the simulator. Once the application is running, click inside the text field and enter a Fahrenheit temperature. Next, click on the Convert button to display the equivalent temperature in Celsius. Assuming all went to plan your application should appear as outlined in the following figure (note that if the keyboard obscures the result label you will need to reload the user interface design into Interface Builder and move the label, button and text field objects so that they are all positioned in the top half of the view):IOSBOXif(typeof ez_ad_units!='undefined')ez_ad_units.push([[970,250],'techotopia_com-leader-1','ezslot_4',157,'0','0']);__ez_fad_position('div-gpt-ad-techotopia_com-leader-1-0');SummaryIn this chapter we have put into practice some of the theory covered in previous chapters, in particular the separation of the view from the controller, the use of subclassing and the implementation of the Target-Action pattern through the use of actions and outlets.

In its first version, from 1991 to 1995, Unicode was a 16-bit encoding, but starting with Unicode 2.0 (July, 1996), the Unicode Standard has encoded characters in the range U+0000..U+10FFFF, which amounts to a 21-bit code space. Depending on the encoding form you choose (UTF-8, UTF-16, or UTF-32), each character will then be represented either as a sequence of one to four 8-bit bytes, one or two 16-bit code units, or a single 32-bit code unit.

There are several possible representations of Unicode data, including UTF-8, UTF-16 and UTF-32. They are all able to represent all of Unicode, but they differ for example in the number of bits for their constituent code units.

The freely available open source project International Components for Unicode (ICU) has UTF conversion built into it. The latest version may be downloaded from the ICU Project web site. Many other libraries may have built-in converters, so you may not have to write your own. [AF]

UTF-16 and UTF-32 use code units that are two and four bytes long respectively. For these UTFs, there are three sub-flavors: BE, LE and unmarked. The BE form uses big-endian byte serialization (most significant byte first), the LE form uses little-endian byte serialization (least significant byte first) and the unmarked form uses big-endian byte serialization by default, but may include a byte order mark at the beginning to indicate the actual byte serialization used. [AF]

A different issue arises if an unpaired surrogate is encountered when converting ill-formed UTF-16 data. By representing such an unpaired surrogate on its own as a 3-byte sequence, the resulting UTF-8 data stream would become ill-formed. While it faithfully reflects the nature of the input, Unicode conformance requires that encoding form conversion always results in a valid data stream. Therefore a converter must treat this as an error. [AF]

Originally, Unicode was designed as a pure 16-bit encoding, aimed at representing all modern scripts. (Ancient scripts were to be represented with private-use characters.) Over time, and especially after the addition of over 14,500 composite characters for compatibility with legacy sets, it became clear that 16-bits were not sufficient for the user community. Out of this arose UTF-16. [AF]

Surrogates are code points from two special ranges of Unicode values, reserved for use as the leading, and trailing values of paired code units in UTF-16. Leading surrogates, also called high surrogates, are encoded from D80016 to DBFF16, and trailing surrogates, or low surrogates, from DC0016 to DFFF16. They are called surrogates, since they do not represent characters directly, but only as a pair.

UTF-16 sometimes requires two code units to represent a single character. It is therefore a variable width encoding, and just like some of the East Asian legacy character sets such as Shift-JIS (SJIS) code units alternate between two widths. People familiar with these character sets are well acquainted with the problems that variable-width codes can cause. However, there are some important differences between the mechanisms used in SJIS and UTF-16:

With UTF-16, relatively few characters require 2 units. The vast majority of characters in common use are single code units. Even in East Asian text, the incidence of surrogate pairs should be well less than 1% of all text storage on average. (Certain documents, of course, may have a higher incidence of surrogate pairs, just as phthisique is an fairly infrequent word in English, but may occur quite often in a particular scholarly text.) 2ff7e9595c