If you want to be proficient in the writing of code in the C programming language, you must have a thorough working knowledge of how to use pointers. One of those things, beginners in C find difficult is the concept of pointers. The purpose of this unit is to provide an introduction to pointers and their efficient use in the C programming. Actually, the main difficulty lies with the C’s pointer terminology than the actual concept.
C uses pointers in three main ways. First, they are used to create dynamic data structures: data structures built up from blocks of memory allocated from the heap at run-time. Second, C uses pointers to handle variable parameters passed to functions. And third, pointers in C provide an alternative means of accessing information stored in arrays, which is especially valuable when you work with strings.
A normal variable is a location in memory that can hold a value. For example, when you declare a variable i as an integer, four bytes of memory is set aside for it. In your program, you refer to that location in memory by the name i. At the machine level, that location has a memory address, at which the four bytes can hold one integer value.
A pointer is a variable that points to another variable. This means that it holds the memory address of another variable. Put another way, the pointer does not hold a value in the traditional sense; instead, it holds the address of another variable. It points to that other variable by holding its address.
Because a pointer holds an address rather than a value, it has two parts. The pointer itself holds the address. That addresses points to a value. There is the pointer and the value pointed to. As long as you’re careful to ensure that the pointers in your programs always point to valid memory locations, pointers can be useful, powerful, and relatively trouble-free tools.
We will start this tutorial with a basic introduction to pointers and the concepts surrounding pointers, and then move on to the three techniques described above. Thorough knowledge of the pointers is very much essential for your future tutorials like the data structures etc..