[WIP]
The concept of pointer in C is one of the most feared concepts, but with a little bit of effort, it’s easily understood. However, even after understanding, because there are many small concepts, we need a quick reference that can help us recall the workings. I hope this post serves as both.
Q. What exactly is a pointer?
A. The K&R book provides the best succinct definition of a pointer:
A pointer is a variable that contains address of another variable
Q. Can you give me an example of a pointer and it’s usage?
A. We take a data type in C, say int, then a pointer to a variable of this type would be denoted by int*. Let’s see an example:
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int x, *px;
x = 10;
px = &x;
Here, px is a pointer that will hold the address of an integer and in this case, it holds the address of x in particular. The & operator is what gets the address of x. To access the variable x, we can dereference using the operator * where needed like:
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printf("Value of x is %d\n", *x);
*x = 5;
printf("New value of x is %d\n", *x);
And this should give us when executed:
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$ Value of x is 10
New value of x is 5
Q. Why do we need pointers?
A. There are two ways to pass data between functions:
Pass by value and Pass by reference