Not the requirement of the Internet: DOS

Explanation:
The Internet is a global network of interconnected computers that allows for the exchange of information and communication between users. It requires several components to function properly. Let's discuss each of these components in detail:

1. Operating System:
An operating system is a software that manages computer hardware and software resources and provides common services for computer programs. It is a crucial requirement for the Internet as it controls the computer's operations and allows users to interact with various applications and services on the Internet.

2. Web Browser:
A web browser is a software application that allows users to access and view websites on the Internet. It interprets the HTML, CSS, and JavaScript code of a webpage and displays the content in a user-friendly manner. Web browsers such as Google Chrome, Mozilla Firefox, and Microsoft Edge are widely used to access the Internet.

3. Modem:
A modem is a device that connects a computer or a network to the Internet. It modulates and demodulates digital data into analog signals that can be transmitted over telephone lines or cable lines. It plays a crucial role in establishing a connection between the user's device and the Internet service provider (ISP).

4. DOS (Disk Operating System):
DOS is an early operating system developed by Microsoft that was widely used in the 1980s and early 1990s. It was primarily designed for personal computers and lacked graphical user interfaces. However, DOS does not provide the necessary functionalities to connect to and browse the Internet. It requires additional software such as a terminal emulator or a TCP/IP stack to establish an Internet connection, which makes it an unsuitable choice for accessing the Internet directly.

In conclusion, the requirement of the Internet includes an operating system, a web browser, and a modem. However, DOS is not a requirement as it does not provide the necessary functionalities to connect to and browse the Internet.