As mentioned in previous sections, it is good practice to give the user the opportunity to specify such options as window sizes, colours, fonts, labels, etc. for an application. This flexibility is achieved using client resources, which are variables that can be set either externally with respect to the application, in various text files etc., or they can be set internally within the program code, by the programmer. Programmers and users of an application written using a widget set will make heavy use of this facility. Managing widget resource settings from external sources is complex and requires a more detailed discussion and is the purpose of this section.