INTRODUCTION TO POINTERS IN C

Introduction to pointers in C

• DIFFERENT ASPECTS OF USING POINTERS IN OTHER METHODS IN C
• C POINTERS OPERATORS 
• ADVANTAGES 
• USES
• NULL POINTER
• COMPLEX POINTER 

Going back to what we discussed before, a pointer is a variable in C that stores the address of a location in memory. To access and modify data stored in a variable's memory, a pointer is a useful tool.

One of the most interesting and unusual aspects of C is its pointers. The tongue becomes more flexible and potent as a result. The advice can seem complicated and challenging at first, but if you get it, trust me—C opens up a world of opportunities.

When a variable is declared in a program, the system specifies where in memory the value should be stored. According to the software up above, we can get this place's address.

Assume for the purposes of argument that the system has reserved 80F in memory.

 

Int n=10

Int p=&n

 

Declaring a pointer

 

In C, a pointer can be declared using the * (letter symbol). Also known as an indirect pointer, it is used to dereference a pointer.

 

1. int *a;//pointer to int  
2. char *c;//pointer to char

the help of * (indirection operator), we can print the value of pointer variable p.

Let's see the pointer example as explained in the above figure.

 

Now we will understand different aspects of using pointers in other methods using C

 C Pointer Operators

Two distinct kinds of pointer operators exist in C:

•    operator and
•     & operato

Operators in C have been examined in detail in distinct sections.

The operand's memory address is returned by the & operator. As an illustration,

a = &b;

The memory address of variable b will be saved in variable a.

The counterpart of & is the * operator. The value found at the specified location is returned by this operator.

For instance, if the variable's memory location is included in a, then the code,

c is equal to *a;

will cause the variable's value to be stored in c.

let us understand the pointer in C with a C program

Advantages of using pointer

·       When dealing with arrays and C structures, pointers are the way to go.
It is simpler to pass functions as parameters to other functions when pointers are used because they permit references to functions.
• A C function can change its arguments sent to it using Pointers.
• The program's size and runtime are reduced thereafter.
• It makes it possible for C's dynamic memory management to work.

Usage of pointers

The C language has several uses for pointers.

1) Allocating memory dynamically

We may utilize the pointer-based malloc() and calloc() methods in the C language to dynamically allocate memory.

2) Structures, Functions, and Arrays

In C, pointers are often utilized in arrays, functions, and structures. It increases performance and decreases code.

NULL Pointer

The NULL pointer is a pointer that is only NULL and has no value assigned to it. If you declare the pointer without an address to provide, you can set its value to NULL. It will provide a better approach.

Int *p=NULL;

Most of the time in libraries of it may have value 0

Let us try one C program to swap two numbers using 3^rd variable

Reading complex pointers

Several things must be taken into consideration while reading the complex pointers in C. Let’s see the precedence and associativity of the operators that are used regarding pointers.

• Here in the above table, please mark

  • The bracket operator, denoted by the symbol (), is used to declare and define the function.
  • An array subscript operator is used here: This is known as the pointer operator.
  • A pointer's name serves as its identifier. There is never going to be anything more important than this.
  • Kind of information: A pointer's data type identifies the sort of variable it is pointing to. It also includes other modifiers such as signed int and long.

How to read the pointer: int (*p)[10].

• To interpret the pointer, we must recognize that () and [] are equally precedential. Consequently, we must consider their associativity. The precedence is with (), as the associativity is climbing from left to right.

  The pointer name (identifier) p and the pointer operation * have the same precedence inside the() bracket. Due to their right-to-left associativity, p has precedence over *, with * coming in second.

  As the data type comes first, assign [] the third priority. The pointer will therefore look something like this:

The pointer will be read as p is a pointer to an array of integers of size 10.

Example

How to read the following pointer?

It is read as

Here, "p" designates a function that accepts a void pointer as its second parameter and a two-dimensional array of integers as its first, with an integer as the return type of the letter.

INTRODUCTION TO FUNCTION IN C LANGUAGE

Introduction to function in C

• NEED OF FUNCTION
• ADVANTAGE
• TYPES OF FUNCTION ASPECTS
• DIFFERENT ASPECTS OF FUNCTION CALLING
• C LIBRARY FUNCTION 
• CALL BY VALUE
• CALL BY REFERENCE
• RECURSION
• RECURSIVE FUNCTION 
• MEMORY ALLOCATION OF RECURSIVE FUNCTION 

The basic building block of any C program is functions. A function is a group of statements that receives input, processes it, and then outputs the results. Their symbol is the curly bracket ({}). The ability to call functions repeatedly in C programming allows for more modularity and reuse. This means that you can call the function several times by simply putting in new arguments, saving you from having to write the same code for each input. Putting the code inside a function is one way.

Why do we need a function in C

Because functions offer so many benefits to the developer, we require them in C programming as well as other programming languages. The following are a few main advantages of employing functions:

•  Minimizes redundancy and permits reusability
•  Creates a modular code
• ·Offers abstraction features
• ·The software becomes simple to use and comprehend.
• ·Divides a complex program into manageable chunks

Advantage of function in C

 Programming time can be saved by using functions instead of repeatedly writing the same logic or code.

·    You can call C functions from anywhere in your program, and you can do it as often as you'd like.

·      A large C program that is split up into several functions is easy to manage.

·      The main accomplishment of C functions is their reusability.

·      In C applications, however, calling functions is wasteful by nature.

We may classify function aspects into three categories.

The C function has three components.

 Statement of purpose A function must be defined globally in C for the compiler to understand its name, parameters, and return type.

 Call to function Within the program, functions can be invoked from any location. Function declaration and function calling cannot be different in the argument list. The number of functions that are declared in the function declaration must be passed.

Definition of function the actual assertions that need to be performed are contained in it. When the function is called, control is applied to the most crucial feature. It is important to note that the function can only return a single value at this point. 

Syntax of creating function in C

Reutn_type function_name (data_type parameter)

{

\\ code to be executed

}

Types of function

In C programming, functions come in two varieties:

Numerous methods, including scanf(), printf(), gets(), puts(), ceil(), and floor(), are specified in the C header files. These features are included in the library.

A user-defined function in C is one that the programmer creates for their own usage in the future. Large program code is optimized and made simpler by it. 

 Return value

A C function's return value isn't always guaranteed. If there is no requirement for the function to return any value, use void as the return type. To demonstrate this idea, let's look at a simple C function that outputs nothing.

Example without return value:

Void hello()

{

Printf(“hello c”);

}

Any data type, including char, long, and int, can be used to return any value from the function. The return type of a function is determined by the value that it is expected to return.

This is a simple C function that returns an integer value when given an integer parameter.

Example with return value

Int get()

{

Return (value);

}

 

In the above example we can define any type of data type in the return type whether it is integer or any thing but if we have to pass the float value we have to define first the float and then we can return the value.

 For ex

 

Float get()

{

Return 10.2;

}

Now we have to call the function and get the value.

 

There are different aspects of function-calling

 

A function can accept or reject an argument. It can return a value or not. Based on the above, there are four types of function calls:

 

      A function that does not require parameters
Yields no value in return, as well as one that does
Process that requests parameters but yields no output
Execute a program with parameters and display the outcomes

 

let us understand this by an example of a function without argument and return value.

 

 

Now let's understand this for function without argument and with return value

 

Let us understand this by with function and with return value

 

 printf("\nEnter two numbers:");  

C library functions

 

C comes with a set of functions that are stored in a library. With the help of these capabilities, you may accomplish certain activities more easily. The (printf) library function, for instance, allows you to output to the console.

Compiler designers create library functions. Several header files that conclude in. h are used to define the functions that comprise the C standard library. We must include the library functions defined in these header files for our software to use them.

For example, we need to include stdio. h in our application to use library functions like (printf) and (scanf). The library's standard input/print functions are all contained in this header file.

 

Let us better understand this by the table given below

 

Call by value in C

 

There are two methods to pass the value into the function

1)      call by value

2)      call by reference

 

 1) call by value 

• Transforming the value of the real parameters into their formal counterparts is the essence of the call-by-value technique. Another way of putting it is that the value method call is where the function call makes use of the variable's value.
• A call-by-value method does not allow the use of formal parameters to modify the value of actual parameters.
• Separate memory is allocated for the two sorts of parameters because, in a call-by-value, the value of the real parameter is copied to the formal parameter.
• In function calls, parameters are considered real, although in function definitions, they are considered formal.

Let us better understand the concept of call by value in a  C program

 

 Call by reference in C

• In a comparison call, the address of the variable is actually passed as an argument to the function call.
• Their addresses are included, therefore the parameters are passed.
• Memory is allotted in the same way for formal and actual parameters by reference. All function operations use the value stored in the real parameter address; the updated value is likewise recorded at the same address.

 

Let us try a C program having call by reference 

 

 Difference between call by value and call by reference

 

 

Recursion in C language

 

When a function calls itself to solve a lesser problem, it is called recursion. When a function calls itself, we say that it is recursive. Another name for this type of call is "recursive call.".

A recursion is a way of invoking itself again. However, to end the loop, you must declare the condition. Recursive code is both shorter and more complex than iterative code, which is lengthier and easier to grasp.

Recursion works well for projects with linked subtasks, albeit it isn't suitable for every task.

For instance, sorting, finding, and navigation difficulties may all be tackled with recursion.

Recursion is usually less efficient than iterative methods as the function call is always unnecessary.

Any problem with a recursive solution can have iterative solutions. However, for some problems, such as factorization, the Tower of Hanoi, and the Fibonacci sequence, recursion is the best approach.

 

Let us understand recursion by a simple C program

Recursive function

 

To complete an operation, a recursive function breaks it down into smaller stages. One way a subtask might perform a function is by adhering to an end condition. Once the function returns the final result, the recursion is ended.

The recursive scenario depicts a function that calls itself to perform a subtask, whereas the basic example describes a function that does not iterate. This format works with all recursive functions.

 

The pseudocode for writing any recursive function is given below.

The pseudocode

 

Let us now understand this by a C program having Fibonacci series

 

 

Memory allocation of recursive function

 

With every iteration of this method, a fresh memory copy is produced. After data is returned by the process, the copy is removed from memory. Since the stack holds all of the variables and other items defined inside a function, each recursive call maintains its own stack.

Every time a value is returned by the related function, the stack is cleared. Recursion becomes extremely difficult when one considers the tracking and resolution of the values of each recursive call. This makes stack management and monitoring the values of the variables declared there very important.

To have a better understanding of memory allocation in recursive functions, let's examine the following example