Book Image

Practical C Programming

By : B. M. Harwani
Book Image

Practical C Programming

By: B. M. Harwani

Overview of this book

Used in everything from microcontrollers to operating systems, C is a popular programming language among developers because of its flexibility and versatility. This book helps you get hands-on with various tasks, covering the fundamental as well as complex C programming concepts that are essential for making real-life applications. You’ll start with recipes for arrays, strings, user-defined functions, and pre-processing directives. Once you’re familiar with the basic features, you’ll gradually move on to learning pointers, file handling, concurrency, networking, and inter-process communication (IPC). The book then illustrates how to carry out searching and arrange data using different sorting techniques, before demonstrating the implementation of data structures such as stacks and queues. Later, you’ll learn interesting programming features such as using graphics for drawing and animation, and the application of general-purpose utilities. Finally, the book will take you through advanced concepts such as low-level programming, embedded software, IoT, and security in coding, as well as techniques for improving code performance. By the end of this book, you'll have a clear understanding of C programming, and have the skills you need to develop robust apps.
Table of Contents (20 chapters)

Encrypting a file

Encryption means converting content into a coded format so that unauthorized persons will be unable to see or access the original content of the file. A text file can be encrypted by applying a formula to the ASCII value of the content.

The formula or code can be of your choosing, and it can be as simple or complex as you want. For example, let's say that you have chosen to replace the current ASCII value of all letters by moving them forward 15 values. In this case, if the letter is a lowercase a that has the ASCII value of 97, then the forward shift of the ASCII values by 15 will make the encrypted letter a lowercase p, which has the ASCII value of 112 (97 + 15 = 112).

In this recipe, I assume that a sequential file that you want to encrypt already exists. Please read Appendix A to learn how to create a sequential file. You can also refer to Appendix A...