futter and dart programming language, Summaries of Web Application Development

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Session 1

Main topics:

• Intro to programming
• Intro to dart language
• Data types in Dart

Intro to programming

- What is Programming?

In a simple answer, “Programming is the act of instructing computers to carry out tasks.” It is often referred to as coding. So then, what is a computer program? A computer program is a sequence of instructions that the computer executes. Computer in the definition above is any device that is capable of processing code. This could be smartphones, ATMs, Conditioners, Traffic lights, Servers to name a few.

- The Natural Language of the Computer

Machines have their natural language like humans do. Computers do not understand the human language. The natural language of computers is the binary code (1 and 0) These represent two states: on (1) and off (0). That is the natural language of electronic equipment. It would be hectic for us as humans to communicate with the computer in binary. To communicate with machines who speak binary, we do so in a language that’s closer to our own natural language. Such as English, French, Swahili or Arabic. Programming languages are close to our natural languages. But they are more structured and must be thoroughly learned.

**1. Go straight

2. Drive half kilometer
3. Take left
4. Drive around one kilometer
5. Search for KFC at your right side** Now, try to map the situation with a computer program. The above sequence of instructions is actually a Human Program written in English Language, which instructs on how to reach KFC from a given starting point. This same sequence could have been given in Spanish, German, Arabic, or any other human language, provided the person seeking direction knows any of these languages. Now, let's go back and try to understand a computer program, which is a sequence of instructions written in a Computer Language to perform a specified task by the computer. Following is a simple program written in Dart programming Language --

The above computer program instructs the computer to print "Hello,World!" on the computer screen. A computer program is also called a computer software , which can range from two lines to millions of lines of instructions. Computer program instructions are also called program source code and computer programming is also called program coding. A computer without a computer program is just a dump box ; it is programs that make computers active.

- Algorithm From programming point of view, an algorithm is a step-by-step procedure to resolve any problem. An algorithm is an effective method expressed as a finite set of well-defined instructions. Thus, a computer programmer lists down all the steps required to resolve a problem before writing the actual code. Following is a simple example of an algorithm to find out the largest number from a given list of numbers

- What is Dart? Dart is an open-source, general-purpose, object-oriented programming language with C-style syntax developed by Google in 2011. The purpose of Dart programming is to create a frontend user interfaces for the web and mobile apps. It is under active development, compiled to native machine code for building mobile apps.

- Let’s dive in, after install dart on your machine refer to this instructions, we can go through some fundamentals: - dart:core library contains built-in types, collections, and other core functionality for every Dart program. - dart:core library automatically imports to every Dart program. - Dart is a single thread programming language like 'JavaScript' - Dart source file extension is .dart - Every Dart statement ends with a semicolon ; - main() is the entry point of a Dart program. Every app or program must have a top-level main function.

Data Types

The Dart language supports the following types:

• Numbers (1, 2,… - 1.2, 468.654 - (-156) - 65489984984)
• Strings (‘Mohammed’ – ‘A’ – “اهال”)
• Booleans (true, false)
• Lists ( [1,2,3,4,5] )
• Maps ( <Name – Khaled>, <Age, 26>

Numbers Numbers in Dart are used to represent numeric literals. The Number Dart come in two flavors:-

• Integer − Integer values represent non-fractional values, i.e., numeric values without a decimal point. For example, the value "10" is an integer. Integer literals are represented using the int keyword.
• Double − Dart also supports fractional numeric values i.e. values with decimal points. The Double data type in Dart represents a 64-bit (double-precision) floating-point number. For example, the value "10.10". The keyword double is used to represent floating point literals.

Boolean The Boolean data type represents Boolean values true and false. Dart uses the bool keyword to represent a Boolean value.

List and Map The data types list and map are used to represent a collection of objects. A List is an ordered group of objects. The List data type in Dart is synonymous to the concept of an array in other programming languages. The Map data type represents a set of values as key-value pairs.

The Dynamic Type Dart is an optionally typed language. If the type of a variable is not explicitly specified, the variable’s type is dynamic.

Variables A variable is “a named space in the memory” that stores values. In other words, it acts a container for values in a program. Variable names are called identifiers. Following are the naming rules for an identifier:

• Identifiers cannot be keywords.
• Identifiers can contain alphabets and numbers.
• Identifiers cannot contain spaces and special characters, except the underscore (_) and the dollar ($) sign.
• Variable names cannot begin with a number. Type Syntax A variable must be declared before it is used. Dart uses the var keyword to achieve the same. The syntax for declaring a variable is as given below: var name = 'Abdallah'; All variables in dart store a reference to the value rather than containing the value. The variable called name contains a reference to a String object with a value of 'Abdallah'. Dart supports type-checking by prefixing the variable name with the data type. Type-checking ensures that a variable holds only data specific to a data type. The syntax for the same is given below: String name = 'Abdallah'; int num = 10;

The dynamic keyword Variables declared without a static type are implicitly declared as dynamic. Variables can be also declared using the dynamic keyword in place of the var keyword. Final and Const The final and const keyword are used to declare constants. Dart prevents modifying the values of a variable declared using the final or const keyword. These keywords can be used in conjunction with the variable’s data type or instead of the var keyword. The const keyword is used to represent a compile-time constant. Variables declared using the const keyword are implicitly final.

Note : Only const variables can be used to compute a

compile time constant. Compile-time constants are

constants whose values will be determined at compile time

Thanks, Good Luck!