What is Software Engineering?

Software engineering is defined as a process of analyzing user requirements and then designing, building, and testing software application which will satisfy those requirements.

Let's look at the various definitions of software engineering:

• IEEE, in its standard 610.12-1990, defines software engineering as the application of a systematic, disciplined, which is a computable approach for the development, operation, and maintenance of software.
• Fritz Bauer defined it as 'the establishment and used standard engineering principles. It helps you to obtain, economically, software which is reliable and works efficiently on the real machines'.
• Boehm defines software engineering, which involves, 'the practical application of scientific knowledge to the creative design and building of computer programs. It also includes associated documentation needed for developing, operating, and maintaining them.'

History Of Software

The Early Days of Software

Computer scientist Tom Kilburn is responsible for writing the world’s very first piece of software, which was run at 11 a.m. on June 21, 1948, at the University of Manchester in England. Kilburn and his colleague Freddie Williams had built one of the earliest computers, the Manchester Small-Scale Experimental Machine (also known as the “Baby”). The SSEM was programmed to perform mathematical calculations using machine code instructions. This first piece of software took “only” 52 minutes to correctly compute the greatest divisor of 2 to the power of 18 (262,144).

For decades after this groundbreaking event, computers were programmed with punch cards in which holes denoted specific machine code instructions. Fortran, one of the very first higher-level programming languages, was originally published in 1957. The next year, statistician John Tukey coined the word “software” in an article about computer programming. Other pioneering programming languages like Cobol, BASIC, Pascal and C arrived over the next two decades.

The Personal Computing Era

In the 1970s and 1980s, software hit the big time with the arrival of personal computers. Apple released the Apple II, its revolutionary product, to the public in April 1977. VisiCalc, the first spreadsheet software for personal computing, was wildly popular and known as the Apple II’s killer app. The software was written in specialized assembly language and appeared in 1979.

Other companies like IBM soon entered the market with computers such as the IBM PC, which first launched in 1981. The next year, Time magazine selected the personal computer as its Man of the Year. Again, software for productivity and business dominated these early stages of personal computing. Many significant software applications, including AutoCAD, Microsoft Word and Microsoft Excel, were released in the mid-1980s.

Open-source software, another major innovation in the history of software development, first entered the mainstream in the 1990s, driven mostly by the use of the internet. The Linux kernel, which became the basis for the open-source Linux operating system, was released in 1991. Interest in open-source software spiked in the late 1990s, after the 1998 publication of the source code for the Netscape Navigator browser, mainly written in C and C++. Also noteworthy is the release of Java by Sun Microsystems in 1995.

The Mobile Device

The worlds very first mobile phone call was made on April 3, 1973. In 1993 IBM released the first publicly available “smartphone” and in 1996 Palm OS hit the market, bringing PDA’s to the masses. In 1999, RIM released the very first Blackberry 850 device and quickly became the worlds fastest growing company. Then, in 2007, Apple changed computing with the release of the iPhone. This is when mobile computing really found it’s place and mobile applications began to explode. Mobile apps are now a major part of development using languages like Swift and Java.

Software Development Today

Today, software has become ubiquitous, even in places that you might not expect it, from crock pots to nuclear submarines. Some programming languages, like C and Cobol, have survived the test of time and are still in use. Other languages, such as Java and Python, are somewhat younger and have been used in countless software development projects. Still others, such as Apple’s Swift programming language for iOS or Go Open source, are relatively new and exciting.

Types Of Softwares

The two main types of software are system software and application software.

System software is a type of computer program designed to run a computer's hardware and application programs. System software coordinates the activities and functions of the hardware and software. In addition, it controls the operations of the computer hardware and provides an environment or platform for all the other types of software to work in. The best-known example of system software is the operating system (OS), which manages all the other programs in a computer.

Application software is a computer software package that performs a specific function for an end user or, in some instances, for another application. An application can be self-contained or a group of programs. The program is a set of operations that runs the application for the user. Applications use the computer's OS and other supporting programs, typically system software, to function. Application software is different than other software that might come pre-bundled with a computer's operating system, such as a utility.

Software

Software is a set of instructions, data or programs used to operate computers and execute specific tasks. Opposite of hardware, which describes the physical aspects of a computer, software is a generic term used to refer to applications, scripts and programs that run on a device. Software can be thought of as the variable part of a computer, and hardware the invariable part.

Software is often divided into categories. Application software refers to user-downloaded programs that fulfill a want or need. Examples of applications include office suites, database programs, web browsers, word processors, software development tools, image editors and communication platforms.

System software includes operating systems and any program that supports application software.

Basic Building Blocks Of The C Programming

You have seen the basic structure of a C program, so it will be easy to understand other basic building blocks of the C programming language.

Tokens in C

A C program consists of various tokens and a token is either a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following C statement consists of five tokens −

printf("Hello, World! \n");
The individual tokens are −
printf
(
   "Hello, World! \n"
)
;

Semicolons

In a C program, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.

Given below are two different statements −

printf("Hello, World! \n");
return 0;

Comments

Comments are like helping text in your C program and they are ignored by the compiler. They start with /* and terminate with the characters */ as shown below −

/* my first program in C */

You cannot have comments within comments and they do not occur within a string or character literals.

Identifiers

A C identifier is a name used to identify a variable, function, or any other user-defined item. An identifier starts with a letter A to Z, a to z, or an underscore '_' followed by zero or more letters, underscores, and digits (0 to 9).

C does not allow punctuation characters such as @, $, and % within identifiers. C is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in C. Here are some examples of acceptable identifiers −

mohd zara abc move_name a_123
myname50 _temp j a23b9 retVal

Keywords

The following list shows the reserved words in C. These reserved words may not be used as constants or variables or any other identifier names.

Whitespace in C

A line containing only whitespace, possibly with a comment, is known as a blank line, and a C compiler totally ignores it.

Whitespace is the term used in C to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the following statement −

int age;

there must be at least one whitespace character (usually a space) between int and age for the compiler to be able to distinguish them. On the other hand, in the following statement −

fruit = apples + oranges; // get the total fruit

no whitespace characters are necessary between fruit and =, or between = and apples, although you are free to include some if you wish to increase readability.

Hello World Example

A C program basically consists of the following parts −

• Preprocessor Commands
• Functions
• Variables
• Statements & Expressions
• Comments

Let us look at a simple code that would print the words "Hello World" −

INPUT

#include <stdio.h>
void main {
   /* my first program in C */
   printf("Hello, World! \n");
   getch;
}

Let us take a look at the various parts of the above program −

• The first line of the program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.
• The next line int main() is the main function where the program execution begins.
• The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program.
• The next line printf(...) is another function available in C which causes the message "Hello, World!" to be displayed on the screen.
• The next line return 0; terminates the main() function and returns the value 0.

Compile and Execute C Program

Let us see how to save the source code in a file, and how to compile and run it. Following are the simple steps −

• Open a text editor and add the above-mentioned code.
• Save the file as hello.c
• Open a command prompt and go to the directory where you have saved the file.
• Type gcc hello.c and press enter to compile your code.
• If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.
• Now, type a.out to execute your program.
• You will see the output "Hello World" printed on the screen.

OUTPUT

Hello, World

Applications of C Programming

C was initially used for system development work, particularly the programs that make-up the operating system. C was adopted as a system development language because it produces code that runs nearly as fast as the code written in assembly language. Some examples of the use of C are -

• Operating Systems
• Language Compilers
• Assemblers
• Text Editors
• Print Spoolers
• Network Drivers
• Modern Programs
• Databases
• Language Interpreters
• Utilities

Audience

This tutorial is designed for software programmers with a need to understand the C programming language starting from scratch. This C tutorial will give you enough understanding on C programming language from where you can take yourself to higher level of expertise.

Prerequisites

Before proceeding with this tutorial, you should have a basic understanding of Computer Programming terminologies. A basic understanding of any of the programming languages will help you in understanding the C programming concepts and move fast on the learning track.