Like Java, the symbols (variables and functions) in C have a scope, which is the part of code within which they are accessible.

The scope system of C is only simpler than that of Java. There is no syntax for a package in C.

global scope

can accessed from anywhere in the program

file scope

can be accessed only within the file in which it is defined

block scope

can only be accessed within the block of code in which it is defined

Keyword static applied to a symbol defined outside any code block in the current file gives the symbol file scope.

Keyword extern means the definition of the symbol is to be found outside this file (so compiler doesn’t complain.)

dangers

Note: scope of a symbol is independent of its type information. If you write code that uses a global function whose prototype has not been provided, the compiler may build the program anyway (it will usually complain though). The result can be bad.

best practice

• keep scope of symbols as tight as possible,
• use header files to communicate type info of shared symbols.