Definitions

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Revision as of 07:23, 14 February 2020 by Vegard (talk | contribs) (→‎C/C++: clarify)
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Definitions and declarations look much the same in C; it can also be difficult to tell the difference between initialization and assignment because they use the same symbol. Here I am just trying to visually lay out the various types of statements in order to show clearly what their differences and relationships are.

C/C++

Variable Function
Type Global Local (Global)
Declaration
extern int x;
extern int fn();
Definition
int x;
int fn() { ... }
Initialization
int x = 1;
Assignment
x = 1;

Note that in this table, "global" and "local" are used both for the type of variable and for the type of scope where the statement appears (if these are different, no code appears in the given cell). For example,

x = 1;

may be used to assign to a global variable, but such a statement may not appear in the global scope. Likewise, you may declare a global variable inside a function (local scope).

See also