If you run script A and then script B in the same workspace, then all variables in A will remain available unless a variable is explicitly cleared or, more commonly, overwritten. This is poor workflow, though. It becomes quite difficult to troubleshoot the origin of variables and how they were changed.
A better idea is to use function input/outputs. If you're working with a lot of variables, you can store them in a structure or cell array to reduce the number of inputs/outputs and to keep your data organized.
Don't use global variable, eval, evalin, etc, to pass variables.
For other opinions on this, see these threads in the forum
