The specifier typedef introduces a synonym for a specified type. The typedef declarations are used to construct shorter or more convenient names for types already defined by the language or declared by the user.

The specifier typedef stands first in the declaration:

typedef synonym as <type_definition>

The typedef keyword assigns synonym to <type_definition>. The synonym needs to be a valid identifier.

A declaration starting with the typedef specifier does not introduce an object or a function of a given type, but rather a new name for a given type. In other words, the typedef declaration is identical to a “normal” declaration, but instead of objects, it declares types. It is a common practice to name custom type identifiers with starting capital letter — this is not required by the mikroBasic PRO for 8051.

For example:

' Let's declare a synonym for "word"
typedef Distance as word

' Now, synonym "Distance" can be used as type identifier: 
dim i as Distance ' declare variable i of word

In the typedef declaration, as in any other declaration, several types can be declared at once. For example:

typedef ^Pti, Array[10] as byte  

Here, Pti is a synonym for type “pointer to int”, and Array is a synonym for type “array of 10 byte elements”.

Here is an example of declaring a synonym for volatile pointer in data space pointing to a byte in code space:

typedef ptrC as ^const code byte data volatile

Now, synonym ptrC can be used as type identifier:

dim ptr as ptrC ' declare variable ptr as volatile pointer in data space pointing to a byte in code space

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