Final answer:
The screen location of the first form is determined by the form's StartPosition property or by explicitly setting the Location property either at design time or at runtime through code in the form's Load event.
Step-by-step explanation:
The screen location of the first form in a project when execution begins is usually determined by the properties of the form which are set at design time or by code at runtime. Specifically, the StartPosition property of a form can be set to determine how the location is calculated. If StartPosition is set to Manual or WindowsDefaultLocation, the operating system chooses the position based on the default algorithm. If set to CenterScreen, the form will be centered on the display. Additionally, the Location property can specify the exact X and Y coordinates of the form's starting position. For more dynamic control, developers may write code in the form's Load event to set the form's position based on certain conditions or computations.