Programming Languages and Program Development

Chapter 13 Objectives

What is programming languages?

The types of generations programming languages

Describe various ways to develop Web pages including HTML, scripting languages, DHTML, XML, and WML.

List the six steps in the program development cycle

Explain the basic control structures used in designing solutions to programming problems.

Computer Programs and Programming Languages

What is programming language?

A program is a sequence of symbols that specifies a computation. A programming language is a set of rules that specify which sequences of symbols constitute a program, and what computation the program describes. Programs and languages can be defined as purely formal mathematical objects.

A programming language is an abstraction mechanism. It enables a programmer to specify a computation abstractly, and to let a program (usually called an assembler, compiler or interpreter) implement the specification in the detailed form needed for execution on a computer.

What are low level languages and high level languages?

Low level languages are machines that dependent that only run on one computer example machine and assembly language. High level languages are often machine independent that can run on many different types of computer

Types of generation programming languages

First generation programming languages

Machine Language only language computer directly recognizes, is the first generation programming language. Machine languages instruction uses series of binary digits (1s and 0s), it could be the combination of numbers and letters that represents binary digits. The binary digit correspond to the on and off electrical state. They are sometimes time consuming and tedious.

Second generation programming languages

Assembly Language is referred to as the second generation of programming language with the assembly language a programmer write instructions using symbols instruction codes, since machine codes are too hard to remember, each processor manufacture designs an “easy-toremember”names for each op-code.programmer writes abbreviations such as A for addition, C for compare, L for load, and M for multiply.

Despite this advantages assembly languages are difficult to learn and understand. The assembly languages must first convert the program to a machine language before the computer can execute, or run, the program. A source programme contains the language instruction, or code to be converted to machine language.

Third generation programming languages

Procedural language are often called third generation programming language, in procedural language the programmer writes instruction that tells the computer what to accomplish and how to do it.it uses series of English like words to write instruction. Most widely used are BASIC, COBOL, and C.

A compiler is a separate program that converts the entire source program into machine language before executing, it stores the object code on storage media for execution later, and it also checks the source program for errors.

An interpreter reads a code statement, converts it to one or more machine language instructions, and then executes those machine language instructions. Program that translates and executes one program code statement at time it does not produce object program.

A sample of machine coding language.

Examples of 3^rd generation languages

The C programming language, Powerful language originally designed to write system software. They requires professional programming skills. Mostly many programmes are written in C. it is used in solving business and scientific problems C runs on almost any type of computer with any operating system, but it is used most often with the UNIX and Linux operating systems.

COBOL (Common Business-Oriented Language) Designed for business applications, English-like statements make code easy to read, write, and maintain. COBOL especially is useful for processing transactions, such as payroll and billing, on mainframe computers. COBOL programs also run on other types of computers.

Object –oriented programming language Used to implement object-oriented design Major benefit is ability to reuse existing objects, C++ and Java are complete object-oriented languages

Java Developed by Sun Microsystems Similar to C++ but uses just-in-time (JIT) compiler to convert source code into machine code

C++ Includes all elements of C, plus additional features for working with object-oriented concepts, Used to develop database and Web applications.

A sample program in c++ coding language

Fourth-generation programming languages

Nonprocedural language that enables users and programmers to access data in a database, popular 4GL is SQL, query language that allows users to manage data in relational DBMS. These powerful languages allow database administrators to define a database and its structure. They also enable users to maintain and access the data in the database.

Fifth –generation programming languages

5GL (Fifth- Generation Language) is also a programming language that uses a visual or graphical development interface to create source language that is usually compiled with a 3GL or 4GL language compiler. 5GL is also known as natural language. Fifth generation programming allows people to interact with computers without needing any specialized knowledge. People can talk to computers and the voice recognition system can convert spoken sounds into written words. Visual programming allows you to easily envision object-oriented programming class hierarchies and drag icons to assemble program components.

Web Development

What is web development?

They are the variety of techniques web developers use to create web pages.

HTML and XHTML

HTML (Hypertext Markup Language) is a special formatting language that programmers use to format documents for display on the Web. You view a Web page written with HTML in a Web browser such as Internet Explorer, Safari, Firefox, Opera, or Google Chrome. Similarly, XHTML (extensible HTML) is a markup language that enables Web sites to be displayed more easily on micro browsers in smart phones and other mobile devices, as well as on desktop and notebook computers. Are not actually programming languages. They are, however, languages that have specific rules for defining the placement and format of text, graphics, video, and audio on a Web page

XML and WML

XML (Extensible Markup Language) allows developers to create customized tags, Server sends entire record to client, enabling client to do much of processing without going back to server. For example, a smart phone, a PDA, and a notebook computer all could display the same XML page or use different formats or sections of the XML page. WML (Wireless Markup Language) allows developers to design pages specifically for micro browsers, Uses wireless application protocol (WAP), standard that specifies how wireless devices communicate with Web. Smart phones and other mobile devices use WML as their markup language.

Scripting languages

Typically easy to learn and use, most popular scripting languages include JavaScript, Perl, PHP, Rexx, Tcl, and VBScript.

JavaScript adds dynamic content and interactive elements to Web page

VBScript (Visual Basic, Scripting Edition) adds intelligence and interactivity to Web page

Perl (Practical Extraction and Report Language) has powerful text processing capabilities

Dynamic HTML (DHTML)

Is a type of HTML that allows Web developers to include more graphical interest and interactivity in a Web page, without the Web page accessing the Web server? That is, the client’s computer automatically updates and changes its own content. Dynamic HTML works by using the document object model, cascading style sheets and scripting language.

The six steps in the program development life cycle

Basically, SDLC consists of all the steps/stages of software starting from its inception to its implementation. There are in fact numerous types of SDLC models (Agile, Waterfall et al) and depending upon your requirements you can choose any of them to meet your purpose.

Given below are some phases, which are common in every SDLC model. Let us go through them to get an idea.

1. Requirement Gathering and Analysis:

Requirement gathering and analysis is the first stage of any SDLC model. This phase is basically the brainstorming phase and often consists of sub-stages like Feasibility Analysis to check how much of the idea can be put into action. If any particular software needs to be modified, the underlying problem(s) of that software is sorted out along with finding ways to solve it.

 2. System Analysis:

This is the second phase of SDLC where the entire system is defined in detail. In fact, it this stage wherein a detailed blueprint of various processes of the software is developed. If needed the system is divided into smaller parts to make it easier more manageable for the developers, designers, testers, project managers and other professionals who are going to work on the software in the latter stages.

3. System Design:

In this phase, the physical system is designed with the help of the logical design prepared by system analysts. The analysts and designers work together and use certain tools and software to create the overall system design, including the probable output.

4. Coding:

As the name implies, in this stage the software is coded with precision. A team of programmers are assigned by the company to work on the software. More often than not, the work is sub-divided under a sub-phase called Task Allocation, where each developer is assigned a part of the work depending on his or her skill set(s). This helps complete the coding efficiently.

5. Testing:

When the software is ready, it is sent to the testing department where Quality Analysts test it thoroughly for different errors by forming various test cases. They either test the software manually or using automated testing tools and ensure that each and every component of the software works fine. Once the QA makes sure that the software is error-free, it goes to the next stage, which is Implementation.

6. Implementation:

This is the final stage of software development life cycle. In this stage, if the software is run on various systems by users. If it runs smoothly on these systems without any flaw, then it is considered ready to be launched.

Basic control structures and design tools used in designing solutions to programming problems

Control Structure

A control structure, also known as a construct, depicts the logical order of program instructions. Three basic control structures are sequence, selection, and repetition.

i)     A selection control structure tells the program which action to take, based on a certain condition. Two common types of selection control structures are the if-then-else and the case. When a program evaluates the condition in an if-then else control structure, it yields one of two possibilities: true or false

ii)      With the case control structure, a condition can yield one of three or more possibilities. The size of a beverage, for example, might be one of these options: small, medium, large, or extra-large. A case control structure would determine the price of the beverage based on the size purchased.

iii)    Repetition Control Structure, the repetition control structure enables a program to perform one or more actions repeatedly as long as a certain condition is met. The two types of repetition control structure are:

a)      Do-while control structure repeats as long as condition is true.

b)      Do-until control structure repeats until condition is true

Design tools in Programming

Design tools it is used by programmers to help document a solution algorithm.

Ø  Program flowchart, graphically shows logic in solution algorithm, connect most symbols on a program flowchart with solid lines. These lines show the direction of the program. Dotted lines on a flowchart connect comment symbols.

Ø  Flowcharting software to develop flowcharts. This software makes it easy to modify and update flowcharts, two popular flowcharting programs are Smart Draw and Visio.