writing simple programs what is the celsius temperature the temperature is degrees fahrenheit what is the celsius temperature the temperature is degrees fahrenheit you can see that susan used the values of and to test her program it looks pretty goodand she is satisfied with her solution she is especially pleased that no debugging seems necessary (which is very unusual elements of programs now that you know something about the programming processyou are almost ready to start writing programs on your own before doing thatthoughyou need more complete grounding in the fundamentals of python the next few sections will discuss technical details that are essential to writing correct programs this material can seem bit tediousbut you will have to master these basics before plunging into more interesting waters names you have already seen that names are an important part of programming we give names to modules ( convertand to the functions within modules ( mainvariables are used to give names to values ( celsius and fahrenheittechnicallyall these names are called identifiers python has some rules about how identifiers are formed every identifier must begin with letter or underscore (the "_characterwhich may be followed by any sequence of lettersdigitsor underscores this implies that single identifier cannot contain any spaces according to these rulesall of the following are legal names in pythonx celsius spam spam spamandeggs spam_and_eggs identifiers are case-sensitiveso spamspamspamand spam are all different names to python for the most partprogrammers are free to choose any name that conforms to these rules good programmers always try to choose names that describe the thing being named one other important thing to be aware of is that some identifiers are part of python itself these names are called reserved words or keywords and cannot be used as ordinary identifiers the complete list of python keywords is shown in table