typedef , arrays, pointers

[bash b]

1)I am reading a code and I want to know the meaning of the following code:

typedef unsigned int e;
typedef unsigned int* r;
typedef unsigned int** a;
typedef unsigned int*** b;
typedef unsigned int**** t;

2)what does it mean having 1, 2, 3 or 4 stars attached to the int or having them atached to the variable for example int **a and int** a.

3)Is it true that int ****t is equivalent to int ***t[] and if this correct what about int *t?

[donbock]

In general, you can read declarations from right to left. Translate each star into the phrase "is a pointer to". Translate "typedef" into "is a synonym for" and insert that phrase immediately after the variable name.

Line 1: e is a synonym for unsigned int.
Line 2: r is a synonym for pointer to an unsigned int.
Line 3: a is a synonym for pointer to a pointer to an unsigned int.
Line 4: b is a synonym for pointer to a pointer to a pointer to an unsigned int.
Line 5: t is a synonym for pointer to a pointer to a pointer to a pointer to an unsigned int.

What's with all this pointer-to-a-pointer stuff? For example, these pointer variables can be initialized as follows. (Notice that the digit I chose to use in the variable names matches the number of stars in the corresponding typedef.)

e v;
r v1;
a v2;
b v3;
t v4;

v1 = &v;
v2 = &v1;
v3 = &v2;
v4 = &v3;

Here's how you could set v to zero using each of these variables (assuming the pointers are initialized as shown above):

v = 0;
*v1 = 0;
**v2 = 0;
***v3 = 0;
****v4 = 0;

It is certainly possible to use high levels of indirection (lots of stars), but I rarely find it useful enough to be worth the confusion. I use one-star indirection every day. I use two-star indirection every so often. I've used three-star indirection a few times in 20+ years. I don't think I've ever used four-star (or higher) indirection.