What is the difference between BASH and DOS ?

BASH is a shell in Linux/UNIX. DOS is one of the old Operating system, and windows still supports DOS commands, you can execute DOS command in Windows command line

BASH commands are case sensitive while DOS commands are not; under BASH, / character is a directory separator and \\ acts as an escape character. Under DOS, / serves as a command argument delimiter and \\ is the directory separator DOS follows a convention in naming files, which is 8 character file name followed by a dot and 3 character for the extension. BASH follows no such convention.