ABSTRACT
Swift has no main method to act as the program's starting point when the operating system loads the application. General programs begin at the first line of code of the program's source file—as is the case in most interpreted languages. A great usability feature sorely missed in previous versions. Moreover, since Xcode 12 is also universal app-ready, it lets student test a single code base across multiple architectures. The “Manually Run” mode means student need to click either click this play button or the blue play icon to run student's code. The automatic mode is not completely error-free. A Swift program consists of various tokens and a token stands for either a keyword, an identifier, a constant, a string literal, or a symbol. Comments are like helping passages in student's Swift program. Variables could be described as reserved memory locations where student could store values.
