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Intro: Accessing variables in a multi-files C program

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• Importance of making the program variables accessible to all functions in the program
  • When you write a computer program, you will use variables to store information needed/used by the statements in the program

  • One important task when you write a (correct) computer program is:

    Making sure that a program variable is accessible in the function(s) that need to make use (= access) of the information stored in that variable

    The scoping rules (that we just learned) will determine which function(s) will be able to access a variable

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• The easy cases: local variables, parameters and static local variables
  • You don't have to worry about the accessibility of local variables, parameters and static local variables, because:

    Due to their scope: Local variables, parameter variables and static local variables are only accessible in one function (i.e.: inside the function where the variable is defined)

    Therefore:

    We do not need to worry about making these kinds of variables accessible in other functions (because they cannot be accessed by other functions....)

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• Making static global variables accessible to all functions (in the same program file)
  • Where can a static global varaible be accessed:

    static global variables are accessible by functions in the same program file

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  • Best practice to ensure that static global variables are most accessible:

    If we define the static global variables at the top of the program file, the all the static global variables will be accessible by all functions in the program file

    Because when the static global variables are defined at the top:

    All functions in the program file will follow after the definition of the static global variables Consequently: All functions in the program file can access the static global variables

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• Important fact about global variables
  • Property of global variables:

    Only the global variables are accessible (= used) by functions (= program statements) in different files !!!

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  • Therefore:

    We need to organize the global variables carefully so they can accessed by all functions in all program files

    We will discuss this in the next webpage....