Learn Functions in C: A Guide to Function Design, Scope, and Storage Classes

 


Functions in C

Functions are an important aspect of programming in C. They allow you to break your code into smaller, reusable parts, making it easier to understand, test, and maintain. In this tutorial, we will discuss how to declare and define functions in C.


Table of Contents

  1. Declaring Functions 
  2. Defining Functions
  3. Function Arguments 
  4. Return Values
  5. Function Scope 
  6. Storage Classes

1. Declaring Functions

Before you can use a function in your program, you need to declare it. A function declaration tells the compiler the name of the function, the type of value it returns (if any), and the types of arguments it expects. Here's the syntax for declaring a function:

rust
return_type function_name(argument_type argument_name, ...);

Let's break down this syntax:

  • return_type is the type of value that the function returns. It can be any valid C data type, including void (if the function does not return a value).
  • function_name is the name of the function. It must be a valid C identifier (i.e., it cannot be a keyword or a variable name).
  • argument_type is the type of the argument that the function expects. You can have multiple arguments, separated by commas. If the function does not take any arguments, you can leave the parentheses empty.
  • argument_name is the name of the argument. It must be a valid C identifier.

Here's an example of a function declaration:

arduino
int sum(int a, int b);

This declaration tells the compiler that there is a function called sum that takes two int arguments (a and b) and returns an int value.

2. Defining Functions

Once you have declared a function, you can define it. A function definition provides the code for the function. Here's the syntax for defining a function:

rust
return_type function_name(argument_type argument_name, ...) {
    // function code goes here
}

Let's break down this syntax:

  • return_type, function_name, argument_type, and argument_name have the same meanings as in the function declaration.
  • The function code goes between the opening and closing curly braces {}.

Here's an example of a function definition:

sql
int sum(int a, int b) {
    int result = a + b;
    return result;
}

This definition provides the code for the sum function that we declared earlier. It takes two int arguments (a and b), calculates their sum, and returns the result as an int value.

3. Calling Functions

To use a function in your program, you need to call it. A function call consists of the function name followed by the arguments in parentheses. Here's the syntax for a function call:

scss
function_name(argument_value, ...)

Let's break down this syntax:

  • function_name is the name of the function you want to call.
  • argument_value is the value you want to pass to the function. If the function takes multiple arguments, you can separate them with commas.

Here's an example of a function call:

sql
int result = sum(3, 5);

This calls the sum function with the arguments 3 and 5. The result of the function (i.e., the sum of 3 and 5, which is 8) is stored in the result variable.

4. Function Arguments

Functions can take zero or more arguments. To pass arguments to a function, we simply list them inside the parentheses when we call the function. For example, here is a function that takes no arguments:

arduino
void greet() {
    printf("Hello, world!\n");
}

And here is how we would call it:

scss
greet();

This would print "Hello, world!" to the console.

Functions can also take arguments of different types. For example, here is a function that takes a string argument:

arduino
void greet(char *name) {
    printf("Hello, %s!\n", name);
}

And here is how we would call it:

scss
greet("John");

This would print "Hello, John!" to the console.

5. Return Values

Functions can also return values. The return type of a function specifies the type of value that the function returns. For example, here is a function that returns an integer value:

arduino
int square(int x) {
    return x * x;
}

And here is how we would call it:

scss
int result = square(5);

This would call the square function with an argument of 5, and store the result in the variable result.

Functions can also return values of different types. For example, here is a function that returns a string:

arduino
char *get_greeting() {
    return "Hello, world!";
}

And here is how we would call it:

scss
char *result = get_greeting();

This would call the get_greeting function and store the result (a string) in the variable result.

6. Function Scope

The scope of a variable refers to the part of the program in which it is visible and accessible. In C, the scope of a variable declared inside a function is limited to that function. This means that the variable can only be accessed and modified from within the function.

For example:

arduino
#include <stdio.h>

void myFunction() {
  int x = 10;
  printf("The value of x is: %d\n", x);
}

int main() {
  myFunction();
  return 0;
}

In the above example, the variable x is declared inside the function myFunction(). The scope of x is limited to myFunction(), which means it cannot be accessed or modified from outside of the function. When myFunction() is called from main(), the value of x is printed to the console.

7. Storage Classes

Storage classes determine the lifetime and visibility of a variable. In C, there are four types of storage classes: auto, static, register, and extern.

  1. auto Storage Class:

Variables declared inside a function without any storage class keyword are by default assigned the auto storage class. auto variables have a local scope and are created every time the function is called. The memory allocated to an auto variable is automatically released when the function returns.

For example:

arduino
#include <stdio.h>

void myFunction() {
  auto int x = 10;
  printf("The value of x is: %d\n", x);
}

int main() {
  myFunction();
  return 0;
}

In the above example, x is declared with the auto storage class. The variable x is local to the function myFunction() and will be automatically destroyed when the function returns.

  1. static Storage Class:

Variables declared with the static keyword are assigned the static storage class. static variables have a local scope and are created when the program starts. The memory allocated to a static variable is not automatically released when the function returns.

For example:

arduino
#include <stdio.h>

void myFunction() {
  static int x = 10;
  x++;
  printf("The value of x is: %d\n", x);
}

int main() {
  myFunction();
  myFunction();
  myFunction();
  return 0;
}

In the above example, x is declared with the static storage class. The variable x is local to the function myFunction() but is created when the program starts. The value of x is incremented every time myFunction() is called and is retained between function calls.

  1. register Storage Class:

The register storage class is used to define local variables that should be stored in a register instead of RAM. This can speed up access to the variable, as registers are faster to access than RAM.

For example:

arduino
#include <stdio.h>

void myFunction() {
  register int x = 10;
  printf("The value of x is: %d\n", x);
}

int main() {
  myFunction();
  return 0;
}

In the above example, x is declared with the register storage class. The variable x is local to the function myFunction() and is stored in a register instead of RAM.

4. register Storage Class:


The typedef storage class is used to create a new type name for an existing type. This can make code easier to read and maintain by providing descriptive names for complex types.

Here's an example of using the typedef storage class:

c
typedef struct {
    int x;
    int y;
} Point;

int main() {
    Point p1 = {1, 2};
    Point p2 = {3, 4};
    printf("p1 = (%d, %d)\n", p1.x, p1.y);
    printf("p2 = (%d, %d)\n", p2.x, p2.y);
    return 0;
}

In this example, the typedef keyword is used to create a new type name Point for a struct containing two integers x and y. This makes it easier to declare variables of this type, as shown in the main() function.

Conclusion

In conclusion, functions are an essential part of C programming. They allow you to break down your code into manageable and reusable parts, making it easier to read and maintain. By defining functions with appropriate arguments and return values, you can create code that is more modular, more organized, and more efficient. Understanding function scope and storage classes is also crucial in writing more advanced C programs. By learning how to use these concepts, you can create functions that are optimized for performance and tailored to the specific needs of your program.


Author
Vaneesh Behl
Passionately writing and working in Tech Space for more than a decade.

Comments

Post a Comment

Popular posts from this blog

17 Best Demo Websites for Automation Testing Practice

Image
We need demo websites for various purposes, like learning new tools and for automation testing practice. In this post, we cherry-picked some of the best websites to practice Selenium automation testing. This set of demo websites would help you to enhance your automation skills.  This post can help various people like,  Automation Testing learners, Experienced professionals, and even Automation Testing tutors/teachers. They all can benefit from these demo websites. Table of Contents 1. Techlistic Automation Practice Form 2. Amazon like Demo E-Commerce Website 3. Make My Trip like Travel Portal 4. Demo Automation Practice Web Table 5. Google.com 6. Demo Website for Handling Alerts 7. Way2Automation Demo 8. NewTours DemoAUT 9. The Demo Site 10. DemoQA 11. Para Bank 12. Orange HRM 13. Sauce Labs Demo E-Commerce Site 14. Demo Bank Demo Websites for API Automation Testing Practice 15. Restful Booker 16. Pet Store 17. Demo REST API Best Demo Websites for Automation Practice Let's take
Read more

Mastering Selenium WebDriver: 25+ Essential Commands for Effective Web Testing

Image
In this tutorial, you will learn about the most important Selenium WebDriver Commands which would be the backbone of your GUI automation scripts.  We have divided the commands in to different categories so that you can learn Selenium commands without difficulty. This Selenium Commands tutorial has explained you all the commands with Code examples and sample Selenium programs for better understanding. Table of Content 1. Selenium Browser Commands 2. Get Commands 3. Navigation Commands 4. Web Element Commands 5. Select Dropdown Commands 1. Selenium Browser Commands Browser commands are the starting point of your Selenium WebDriver script. These commands used to launch browser, maximize it, open URL to be tested and other navigation commands. i. Set Path of browser/driver executable: It is the starting point of the WebDriver script.  You have to download the browser executable file for the browser and make sure it is compatible with the version of your browser. For example, for fir
Read more

Top 7 Web Development Trends in the Market

Image
  Technology continues to advance as humans discover new methods to innovate, doing tasks quicker and more creatively than before. Developers are continuously on the lookout for new technologies that will help them move forward towards a better future.  The contemporary industry is constantly evolving, and new online technologies emerge daily. Entrepreneurs that want to interact with more consumers and stay ahead in this competitive industry may take advantage of these new trends. There aren't many industries that have as much innovation as bespoke web development. Hire WordPress developer to help entrepreneurs interact with more consumers and stay ahead. Websites, without a question, play an important part in today's commercial environment. A WordPress design agency will build you a website that functions as a separate brand, organization, and individual. Doing business on a worldwide scale has become conceivable and attainable as firms and enterprises have transcended all bou
Read more

Mastering Selenium Practice: Automating Web Tables with Demo Examples

Image
Demo Webtable 1 (Static Table) This table has 7 rows and 3 columns. So, the distribution of rows and columns is even. We can assume this table is a static or linear table. This table is easy to automate.  Company Contact Country Google Maria Anders Germany Meta Francisco Chang Mexico Microsoft Roland Mendel Austria Island Trading Helen Bennett UK Adobe Yoshi Tannamuri Canada Amazon Giovanni Rovelli Italy Demo Webtable 2 (Dynamic Table) This table has an uneven distribution of rows and columns the last row has two columns only, but the other rows have 7 columns each. So, let's assume it is a dynamic table. This table is a tougher task. Structure Country City Height Built Rank … Total 4 buildings Burj Khalifa UAE Dubai 829m 2010 1 Clock Tower Hotel Saudi Arabia Mecca 601m 2012 2 Taipei 101 Taiwan Taipei 509m 2004 3 Financial Center China Shanghai 492m 2008 4 Selenium Practice Exercises for Demo Table 2 -  Verify that there are only 4 structure values present in the table with Seleniu
Read more

Automation Practice: Automate Amazon like E-Commerce Website with Selenium

Image
In this post, you will learn to automate different functionalities of an e-commerce website. To automate this practice assignment,  you should have sound knowledge of all the Selenium concepts. We'll create a test plan and then automate an e-commerce website that is quite similar to amazon.com. Automate Amazon-like e-Comm website with Selenium for Automation Practice Table of Content 1. What should you know before starting this Project assignment? 2. Which functionalities will we automate in this Project assignment? 3. Create Test Plan for Amazon like e-commerce website 4. Automate Amazon like e-commerce website: Automate User Registration and Login of e-commerce website Automate Search feature of e-commerce website Automate "Buy Product" feature of e-Commerce website 1. What should you know before automating this automation assignment? You should know the following topics, before starting this project assignment: Software Testing Concept
Read more

Automate GoDaddy.com Features with Selenium WebDriver

Image
This post contains two assignments that helps you to learn Selenium browser commands. These are the simplest assignments. So, this assignment post is the best suited to start your automation tester journey. 1. Automate Browser Actions on GoDaddy.com If you are a beginner in automation testing and looking forward to writing your first Selenium code, then this post is the best destination for you. This assignment will teach you the basic commands of Selenium Webdriver to perform basic actions like., Launch the browser, maximize the browser window, validate the page title, and close the browser. In this post, you will find very basic step-by-step assignments which will upgrade your understanding of Selenium Webdriver and its commands. 1. Test Case - Open Godaddy.com and maximize the browser window. Steps to Automate:
Read more

What Is Artificial Intelligence (AI) and How Does It Work?

Image
Artificial Intelligence, often abbreviated as AI, is a transformative field of computer science that aims to create machines, software, or systems capable of performing tasks that typically require human intelligence. These tasks include problem-solving, learning from experience, understanding natural language, recognizing patterns, and making decisions. In this article, we will explore what AI is, its subfields, and provide examples of AI applications that have already started to shape our world. Understanding Artificial Intelligence AI is a multidisciplinary field that draws inspiration from various areas, including computer science, mathematics, psychology, neuroscience, and linguistics. At its core, AI seeks to replicate or simulate human intelligence in machines, enabling them to perform tasks autonomously, adapt to changing environments, and improve over time. Subfields of Artificial Intelligence AI encompasses several subfields, each with its unique focus and applications: 1. Ma
Read more

Top 10 Highly Paid Indian CEOs in the USA

Image
Top Indian CEOs in the USA Indian Americans have been making significant contributions to the US economy for decades. Many Indian-origin executives have reached the pinnacle of success in American corporations and hold some of the highest-paid positions in the country. In this post, we will take a look at the top 10 highly paid Indian-origin CEOs in the USA, their history, academics, salary, and net worth. 1. Sunder Pichai   Salary US$ 199.7 million Sundar Pichai is the CEO of Google and Alphabet Inc. Born in Tamil Nadu, India, Pichai grew up in a middle-class family and earned a Bachelor’s degree in Metallurgical Engineering from the Indian Institute of Technology in Kharagpur. He went on to earn a Master’s degree in Material Sciences and Engineering from Stanford University and an MBA from the Wharton School of the University of Pennsylvania. Pichai joined Google in 2004 and rose through the ranks to become CEO in 2015. His annual salary in 2021 was $2 million, and his net wort
Read more

How to Automate Google Search with Selenium WebDriver

Image
In this post, you will learn to automate Google Search using Selenium Webdriver with Java. This is a real-time example of Explicit wait command. Google search is an Ajax call. We will handle this Ajax call using the Explicit wait command of Selenium Webdriver. We can also say that we'll automate the auto-suggestion feature of search in this post. 1. What is Ajax search? Ajax stands for Asynchronous JavaScript and XML. Ajax is a new technology for creating faster and more interactive web applications. What Ajax does is: Update a web page without reloading/refreshing it Read data from the server after the page is loaded When you write something into a Search Box say "app" and it shows you similar search options that are Ajax. And you can automate that auto-suggestion box with the help of Explicit command in Selenium WebDriver . Google search is the best example of Ajax. In the case of Google search, you simply type any keyword in the search bar and just below the s
Read more

What is Java Class and Object?

Image
In this Java Class and Object tutorial, we will learn about the fundamentals of Java Programming. Java Class and Object are the base of Java. And we have tried to explain it in a simpler way. For your better understanding, we have also provided example Java programs for concepts of Java Classes and Object and Java Constructors. Classes and Objects are the fundamental building blocks of OOPS (Object Oriented Programming). A Java object is a physical and logical entity whereas a Java class is a logical entity. Table of Content 1. What is a Java Class? Syntax of java Class Explanation of example code Types Of Java Classes 2. What is a Java Object? How to create Java Object? Example Code and it's explanation What is the use of Java Objects? 3. Write your first Java Program - "Hello World" 4. What is Java Constructor? Non-Parameterized Constructor (Default) Parameterized Constructor 1. What is a Java Class? Before creating an object in Java, you need to define a class. A class
Read more