By default, Visual Studio provides two different ways to build your program called Configurations. The two configurations provided for every Fortran project are called the Debug configuration and the Release configuration. Which configuration you are using is visible in the Visual Studio Standard Tool Bar.
Configurations allow you to quickly change how a project is compiled so that you are not labored with the task of having to enter the property pages to change between a debugging compiler setup and a release compiler setup. Settings in one configuration are independent from the settings in a different configuration.
The Debug configuration is used while developing a program to provide the developer with additional information and facilities to help with development and debugging of code. When building and executing programs using the Debug configuration, executable code is initially unoptimized, and debugging information is built in, making the program larger and slower than it might be.
Once all the kinks have been worked out of your program and you are ready to put the code into production, it is time to switch to the Release configuration. When building a solution with the Release configuration, executable code has a moderate level of optimization that is generally considered "safe" for programs that may be susceptible to rounding error.
It is generally advised to make optimizations in the Release configuration or to create your own configuration for optimized settings. It is usually unadvisable to highly optimize the Debug configuration as the optimizer may rearrange or even remove code at high optimization settings, which can limit debugging ability.
New configurations can be created using the Configuration Manager. The configuration manager is accessible from the Solution Configurations dropdown menu or by right-clicking the mouse when hovering over the Solution in the Solution Explorer.