M4 is a macro processing language that has been around since the early 1970s. It was originally designed to assist in the development of the UNIX operating system, but has since been used for a variety of other purposes, such as creating templates for web pages and generating code. In this beginner's guide, we will explore the history of M4, its syntax, and some of its best applications.

History of M4
M4 was created in 1977 by Brian Kernighan and Dennis Ritchie, two of the original developers of the UNIX operating system. Its primary purpose was to assist in the development of the operating system by simplifying the creation of macros, or small programs that could be used repeatedly throughout the code. Over time, M4 became popular in its own right and was eventually included in most UNIX distributions.

Syntax of M4
The syntax of M4 is relatively simple and straightforward. The language uses a series of macros, or predefined commands, that can be combined to create more complex programs. The most common macro in M4 is the define macro, which is used to define a new macro. For example, the following code defines a new macro called "greeting" that will print the string "Hello, world!" when called:

define(`greeting', `Hello, world!')dnl

Once a macro has been defined, it can be called by simply using its name in the code. For example, to call the "greeting" macro defined above, you would use the following code:

greeting

This would output the string "Hello, world!" to the console.

Example of M4 Code
Here is a simple example of M4 code that demonstrates the use of macros to create a more complex program:

define(`name', `John Doe')dnl
define(`age', `30')dnl
define(`job', `Software Engineer')dnl

Hello, my name is `name' and I am `age' years old. I work as a `job'.

When this code is executed, it will output the following string:

Hello, my name is John Doe and I am 30 years old. I work as a Software Engineer.

Applications of M4
M4 has a variety of applications in modern computing. One of its primary uses is in the creation of templates for web pages. By using M4 macros, developers can create reusable code that can be used to generate a large number of similar pages with minimal effort. M4 is also commonly used in software development to generate code automatically. By defining macros that generate code for specific tasks, developers can save time and effort when building complex software systems.

Conclusion
M4 is a powerful macro processing language that has been around for over 40 years. Its simple syntax and flexibility make it a popular choice for a variety of applications, from software development to web design. By following the examples in this beginner's guide, you can start using M4 to create your own macros and streamline your coding workflow.