| 1 | 2 | 3 | 4 |

Shareware software is typically obtained free of charge, either by downloading from the internet or on magazine cover-disks. A user tries out the program, and thus shareware has also been known as 'try before you buy', demoware, trialware and by many other names. A shareware program is accompanied by a request for payment, and the software's distribution license often requires such a payment.

Source code – (commonly just source or code) is any series of statements written in some human-readable computer programming language. In modern programming languages, the source code which constitutes a program is usually in several text files, but the same source code may be printed in a book or recorded on tape (usually without a filesystem). The term is typically used in the context of a particular piece of computer software. A computer program's source code is the collection of files that can be converted from human-readable form to an equivalent computer-executable form.

Spyware - In the field of computing, the term spyware refers to a broad category of malicious software designed to intercept or take partial control of a computer's operation without the informed consent of that machine's owner or legitimate user. While the term taken literally suggests software that surreptitiously monitors the user, it has come to refer more broadly to software that subverts the computer's operation for the benefit of a third party.
T

U
Unix – Unix or UNIX is a computer operating system. Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration. The Unix systems are characterized by various concepts: plain text files, command line interpreter, hierarchical file system, treating devices and certain types of inter-process communication as files, etc. In software engineering, Unix is mainly noted for its use of the C programming language and for the Unix philosophy.

V
Virus - In computer security technology, a virus is a self-replicating/self-reproducing-automation program that spreads by inserting copies of itself into other executable code or documents. A computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells. Extending the analogy, the insertion of a virus into the program is termed as an infection, and the infected file (or executable code that is not part of a file) is called a host. Viruses are one of the several types of malicious software or malware.

W

X
XML - Short for Extensible Markup Language, a specification developed by the W3C. XML is a pared-down version of SGML, designed especially for Web documents. It allows designers to create their own customized tags, enabling the definition, transmission, validation, and interpretation of data between applications and between organizations.