Identifiers in C
Back to Tokens | Back to C Programming | The CompilerThere are 4 types of Identifiers and each type gets its own namespace.
- Label Names, are names that end in a colon, :
- Tags for structure, union, and enumeration types
- Names of Structure or Union members
- Ordinary Identifiers (all others)
struct tag { char tag; ...}
Here you can see we have created a structure with the tag tag, which also has
a member tag of the type char.
int count( struct tag *tag)
{
int len = length( tag->tag)
}
Here you can see we defined the function count with a parameter named tag
which is a pointer to struct tag.In all cases the name tag is in different namespaces and do not conflict.
Identifier Scope
Scopes can confusing, so lets hope we can putthe confusion to rest here.The scope of an identifier generally begins after the declaration except when we define structures, union and enumeration types.
In these cases, the identifier goes into scope immediately, within the declaration itself. So you can used the identifier for recursive definitions.
File Scope
If you declare the identifier outside of all blocks and parameter lists. you can use the identifier anywhere within the translation unit / module.Block Scope
Ignoring lables.An Identifier declared in a block has the scope of the smallest block it is declared in from its location to the end of the block.
The parameters in the function also have block scope.
Function Prototype Scope
Identifiers within parameters of the prototype only have scope in the prototype.Function Scope
Labels are special. They take the full scope of the function, no matter if they are nested within blocks.i.e. you can use them as goto statements.
| 28mar23 | admin |