software Categories

Software Categories

Software can be classified into many categories using various criteria. At this point we will simply differentiate between system programs and application programs. The operating system is the core software of a computer. It performs two important functions. First, it provides a user interface that allows the user to interact with the machine. Second, the operating system manages computer resources such as the CPU and main memory. It determines when programs are allowed to

run, where they are loaded into memory, and how hardware devices communicate.

It is the operating system’s job to make the computer easy to use and to ensure that it runs efficiently.

Several popular operating systems are in use today. The Windows operating system was developed for personal computers by Microsoft, which has captured the lion’s share of the operating systems market.

Various versions of the Unix operating system are also quite popular, especially in larger computer systems. A version of Unix called Linux was developed as an open source project, which means that many people contributed to its development and its code is freely available. Because of that, Linux has become a particular favorite among some users. Mac OS X is an operating system used for

computing systems developed by Apple Computers.

Operating systems are often specialized for mobile devices such as smart phones and tablets. The iOS operating system from Apple is used on the iPhone, iPad, and iPod Touch. It is similar in functionality and appearance to the desktop Mac OS,but tailored for the smaller devices. Likewise, Windows Phone is the version of the Windows operating system from Microsoft used in their phones. Android is a Linuxbased mobile operating system developed by Google and used on many phones.

An application (often shortened in conversation to “app”) is a generic term for just about any software other than the operating system. Word processors, missile control systems, database managers, Web browsers, and games all can be considered application programs. Each application program has its own user interface that allows the user to interact with that particular program.

The user interface for most modern operating systems and applications is a graphical user interface (GUI, pronounced “gooey”), which, as the name implies, makes use of graphical screen elements. Among many others, these elements include

■ windows , which are used to separate the screen into distinct work areas

■ icons , which are small images that represent computer resources, such as a file

■ menus, checkboxes, and radio buttons , which provide the user with selectable

options

■ sliders , which allow the user to select from a range of values

■ buttons , which can be “pushed” with a mouse click to indicate a user selection

The mouse is the primary input device used with GUIs; thus, GUIs are sometimes called point-and-click interfaces . 

The interface to an application or operating system is an important part of the software because it is the only part of the program with which the user interacts directly. To the user, the interface is

the program. Throughout this book we discuss the design and implementation of graphical user interfaces. The focus of this book is the development of high-quality application programs.

We explore how to design and write software that will perform calculations, make decisions, and present results textually or graphically. We use the Java programming language throughout the text to demonstrate various computing concepts.