hen I had to write my first NT service, I went to MSDN and looked for samples. There, I found "Creating a Simple Win32 Service in C++, an article by Nigel Thompson with an example written in C++. Though the article explained the process quite well, I still felt I was missing important information. I wanted to understand what functions are called, by what framework, and when, but C++ didn't make this easy. The object-oriented approach was convenient, but since calls for low-level Win32 functions are encapsulated by class, it is insufficient for learning about the essence of the Services. This is why I feel C is more suitable for the first steps in writing services or for implementing services that perform simple background tasks. C++ is worth using only after you gain a more thorough understanding of the subject. When I had to leave the place I worked and I had to transfer my knowledge to another person, it was very easy to explain the essence of NT services using my examples written in C.

A service is a console application that runs in the background and performs tasks that don't require user interaction. The Windows NT/2000/XP operating systems offer special support for service programs. The installed services can be configured through the Services applet, available from the Control Panel in Windows NT or from Control Panel | Administrative Tools in Windows 2000/XP. Services can be configured to start automatically when operating system starts, so you dont have to start each of them manually after a system reboot.

This article explains how to create a service that periodically queries the amount of available physical memory and writes the result to a text file. The next sections guide you through the process of building, installing, and implementing the service.