If by "uses another created module", you mean using functions / api calls from other module, you can pretty much do that when both modules are activated. Basically it's the same as creating a module but with a dependency in the .info file.
eg. example.module uses wrapper functions from views.module, example.info :
name = Example module
description = "Gives an example of a module."
core = 7.x
package = Views
dependencies[] = views
Comments
If by "uses another created
If by "uses another created module", you mean using functions / api calls from other module, you can pretty much do that when both modules are activated. Basically it's the same as creating a module but with a dependency in the .info file.
eg. example.module uses wrapper functions from views.module, example.info :
More here.