C is a procedural programming language with a static system that has the functionality of structured programming, recursion, and lexical variable scoping. C was created with constructs that transfer well to common hardware instructions. It has a long history of use in programs that were previously written in assembly language. 

C programming language is a machine-independent programming language that is mainly used to create many types of applications and operating systems such as Windows, and other complicated programs such as the Oracle database, Git, Python interpreter, and games and is considered a programming foundation in the process of learning any other programming language. Operating systems and diverse application software for computer architectures ranging from supercomputers to PLCs and embedded systems are examples of such applications.

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History of C language

The C programming language was created at Bell Laboratories in the early 1970s, mainly by Ken Thompson and Dennis Ritchie. For the UNIX operating system, which at the time required applications to be written in assembly language, programmers needed a more user-friendly set of instructions. Assembly programmes, which communicate directly with a computer's hardware, are lengthy and complex to debug, and adding new functionality requires a lot of time and effort.

Thompson's first high-level language was named  B after the BCPL system programming language on which it was built. Thompson rewrote B to better match the demands of the modern time, better system hardware after Bell Labs purchased a Digital Equipment Corporation (DEC) UNIX system model PDP-11. As a result C, the B's successor, was created. By 1973, C had matured to the point that it could be used to rewrite the UNIX operating system.

Other programmers needed documentation that detailed how to use C before it could be utilized effectively outside of Bell Labs. In 1978, Brian Kernighan and Dennis Ritchie's book "The C Programming Language," sometimes known as K&R or the "White Book" by C enthusiasts, became the canonical source for C programming. The second edition of K&R, first published in 1988, is still commonly accessible as of this writing. Based on the book, the first, pre-standard version of C is known as K&R C.

Throughout the 1980s, C developers sought to build standards for the language in order to prevent others from developing their own dialects. The American National Standards Institute (ANSI) standard X3.159-1989 became the official U.S. standard for C in 1989. In 1990, the International Organization for Standardization (ISO) issued the ISO/IEC 9899:1990 standard. These standards, as well as their later updates, are referenced in C versions after K&R. (C89, C90 and C99).

The 1980s saw a surge in operating system development, with C and its use in UNIX being only such instances. Despite its advancements over its predecessors, C was still difficult to use for creating larger software programmes. As computers got more powerful, there was a growing demand for a more user-friendly programming environment. This desire pushed programmers to use C to create their own compilers and, as a result, new programming languages. These new languages may make it easier to code complex operations with many moving elements. For example, object-oriented programming, a programming method that maximizes a programmer's ability to reuse code, was eased by languages like C++ and Java, both of which were derived from C.

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C Basic Commands

Commands

Functions

#include

This is the main header file preprocessor function, which preprocesses standard input and output header files from the C library repository, such as stdio.h, before compiling the programme.

int main()

This C statement, like most programming languages, is the main function, which is the point where the programme execution begins. Once the primary main () has been executed, all other methods and functions are performed.

{

Curly braces are a type of bracket that can be seen in any computer language, not just C. This represents the start of a method or function definition.

/* explanation of C code    */

The text inside the /* and */ tags will be considered as comments and will not be executed or compiled. This is to provide the coder with a clear knowledge of the code and its application or use.

Printf

The output is printed to the console screen using this C command.

Getch()

This function is being used to wait for the user's input.

return 0

This C function returns 0 after terminating the C programme or main function.

}

The function or method block is closed with these curly braces.

//

These are called single line comments, and they are utilized not only in the C programming language but in others as well.

return

The output of the code execution is returned using this function.

\t

This is the function for using a horizontal tab or an empty tab. This belongs to the group of escape sequences and is used to format the programme.

%d

This is the integer type character's format specifier. It's used to make the output seem nice.

Scanf

The user data is taken from the usual console terminal window using this C function.

Let’s write a simple C program using above operators to print hello world:-

#include <stdio.h>

int main (void)

{

    printf("\n Hello World \n");

    return 0;

}

Explanation of above code:

As it can be easily seen, the programme starts with a #. Any line in the C programming language that begins with a # is handled with by the preprocessor at the first stage of the program's execution, the first thing that happens during compilation of this programme is that the line beginning with # is replaced by whatever is in the stdio.h header file.

The following line is 'int main (void)'. This is the start of a function called main, which returns an integer (int) value and takes no arguments (void). It's important to note that every C programme we'll see contains one or more functions. The 'Main' function is where the program's execution begins once it has been run. While all other functions are called from within main or other functions (allowing us to customize the order in which they are called), main is called first from within the system.

After that, you'll notice a curly bracket ({). This essentially determines a function's initial scope. Usually, near the end, you'll notice a reverse curly bracket (}), which indicates the function's end of scope. All of the instructions contained within these brackets are handled as a portion of the function's body.

In the body of the main function, there are two lines of code. 'printf("\n Hello World \n"); . Printf is a function in the system library that outputs formatted strings to STDOUT.It prints anything anyone type inside double quotes (" ") except escape sequences (such as '\n', which is converted to a newline). 'return 0' is the second line of the body. It essentially signals the end of the main function and returns '0' to the function that was called main.

Ultimately, we may expect this code to produce 'Hello World' as its output.

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Use of C and Key Applications

C is one of the oldest and most fundamental programming languages, and it is extensively used all over the world. C is a fast, portable language with a large library. It is a middle-level language with the advantages of both low-level and high-level languages. And it's disheartening to learn that C programming is becoming less popular by the day. C has left an indelible mark on practically every field and is widely used for application development and system development.

Some applications of the C programming language include:

Operating System

The C programming language was created with the intention of writing UNIX operating systems. Furthermore, the execution time of programmes written in C is comparable to that of assembly language, making C the most important component in the development of multiple operating systems. It was used to write the Unix kernel, Microsoft Windows utilities and operating system apps, and a large portion of the Android operating system.

3D Movies

Applications written in C and C++ are commonly used to make 3D videos, because they handle a large quantity of data and do many computations per second, these apps must be extremely efficient and quick. The less time it takes for designers and animators to create movie shots, the more money the corporation saves.

Intermediate Language

C is occasionally used by implementations of other languages as an intermediate language. This method can be used for portability or convenience, as it eliminates the need for machine-specific code generators by using C as an intermediate language. C includes certain characteristics that aid compilation of generated code, such as line-number preprocessor directives and optional unnecessary commas at the end of initializer lists. However, some of C's flaws have encouraged the creation of additional C-based languages, such as, that are expressly designed for usage as intermediate languages.

Play Important Role in Development of New Programming Language

The program written in C is easy and quick to execute. As a consequence, the C programming language has resulted in the creation of many other languages. C++ (also known as C with classes), C#, Python, Java, JavaScript, Perl, PHP, Verilog, D, Limbo, and the Unix C shell are examples of these languages. Every language employs the C programming language to varying degrees. Python, for example, uses C to provide standard libraries, whereas C++, PHP, and Perl need C for their syntaxes and control architectures.

Embedded Systems

The C programming language is the recommended language for creating embedded system drivers and applications. The availability of machine-level hardware APIs, as well as the presence of C compilers, dynamic memory allocation, and deterministic resource consumption, make this language the most popular.

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Reason Behind Popularity of C

For various types of tasks, there are many programming languages that allow developers to be more productive than with C. Higher-level languages have significantly larger built-in libraries that make working with JSON, XML, UI, web pages, client requests, database connections, media bias, and other things much easier.

Regardless, there are many grounds to anticipate that C programming will continue to be popular for a long time.

Portability and Efficiency

C is an assembly language that may be used anywhere. It's as near to the machine as possible while being virtually compatible with existing processor designs. And  practically every technology, there is at least one C compiler. Nowadays, because new compilers generate highly optimized binaries, improving their output using hand-written assembly is difficult.

Memory Manipulation

C's ability to access arbitrary memory addresses and perform pointer arithmetic is a key feature that makes it ideal for system programming (operating systems and embedded systems).

Computer systems and microcontrollers map their peripherals and I/O pins into memory locations at the hardware/software boundary. To communicate with the outside world, system applications must read and write to those particular memory regions. As a result, the ability of C to manipulate independent memory addresses is critical for system programming.

Resources Are Used in a Definite Way

Garbage collection, or even dynamic allocation for certain embedded systems, is a common language feature that system programming cannot rely on. Embedded apps have a certain amount of time and memory. They're frequently used in real-time systems in which a non-deterministic garbage collector call isn't an option. If dynamic allocation is not possible due to a paucity of memory, it is critical to have additional memory management mechanisms in place, such as the ability to place data in custom addresses using C pointers. Languages that rely significantly on dynamic allocation and trash collection would be unsuitable for resource-constrained environments.

Why Learn C Language?

There are a plethora of programming languages to choose from, ranging from the incredibly high level (such as Visual Basic) to the low level power of assembly, and a wide range of specialized possibilities in between (Perl, Ruby, and Python are good choices for many tasks). Java has also become a popular programming language for certain tasks, in part due to its extensive API and in part due to the virtual machine's security features.

Nonetheless, there are some compelling reasons to master C programming. First, it's been used by programmers for 30 years, and there is a wealth of source code. This means there's a lot to learn and a lot to put into practice. Furthermore, many of the language's problems have been clarified and it's well-understood among programmers, and there are numerous tutorials accessible.

C has become something of a programming universal language as a result of its antiquity and employment as the language of system programming for Unix. C is a fantastic language for describing common programming concepts in a form that most people can understand. Furthermore, many of the principles used in C, such as argc and argv for command line parameters, loop constructions, and variable types, will appear in many other languages we learn, allowing us to communicate with others even if they don't know C in a way that is understandable to both of us.

To add on to that, C is in close proximity to the machine. When you're dealing with pointers, bytes, and individual bits, optimization techniques become a lot more intuitive. Understanding exactly how things work below the hood is also useful; it helps a lot when something you're attempting to perform in a higher-level language seems to take a long time or doesn't function at all. You also have a better understanding of advanced issues, such as how connectivity works. It will be a little bit easier with a higher-level programming language, but it will be more difficult to comprehend what's going on, and when things stop working, it's much preferable to know exactly what's going on so you can repair it.

C has 32 keywords, a variety of data types, and a set of system utilizing functions that make programming simple.

Another property of 'C' programming is its ability to self-extend. Various functions from a library are included in a 'C' programme. We have the option of adding our own features and functions to the library. In our application, we can access and use these functions whenever we want. This capability makes working with sophisticated code much easier.

There are a number of compilers on the market that may be used to run programmes written in this language.

How C Programming Language Works?

C is a compiled programming language. This mean that we'll have to convert our source files (human-readable text files) into object files (machine-readable text files for microcontrollers, computers, and laptops).

Editing

Writing/editing source code is the initial stage in constructing an application in C. The source code is a text file that contains all of the instructions that must be executed by the machine (understandable by humans).

We can use either a plain text editor (like Notepad) or the IDE's built-in editor. The source code must follow the syntax of the C programming language. After the source file is complete, save it as a *.c file.

We'll need a compiler to compile our source code. We'll need to install a C compiler on our PC and run it manually from the command prompt if we utilize a simple text editor for our source code. An easier method is to utilize an IDE (which should have a compiler) and simply press a menu button to start it.

A preliminary processing phase of the source file is included in the compilation task. A preprocessor is called by the compiler to perform the preprocessing. The preprocessor searches the source code for lines that begin with the # (hash) character. 

Including functions declared externally from our source code is one of the compiler's directives. The preprocessor removes all compiler directives from the original code, but it keeps track of which extra files are required later in the process. A temporary file will be created at the end of the preprocessing, which will be hidden from the user.

The compiler starts after the preparation is finished. Our source file is converted into an object file by the compiler. The object file, also known as machine code, can be interpreted by the computer's or microcontroller's Central Processing Unit.

The object file is complete, however, some undefined references are missing. These undefined references are code fragments that must be fetched from a separate location. The printf() function is the undefined reference in our scenario. We know where to acquire the code for this function because the compiler directive (#includestdio.h>) mentioned it.

stdio.h is a header file (extension *.h) that contains the declaration of our printf() function, among other things. We describe where to get the definition of the printf() function by including the header file.

Linking

At this point, we must gather all of the files required by our application. For the external functions, we'll need the object files as well as the static library files. The external functions utilized in our source file are defined in the static library files (*.lib). The machine code for the printf() function will be stored in the static library file in our scenario.

A linker is the one who does the linking. It will examine all of the object files for undefined references and replace them with the machine code from the library files. We'll have an executable file (*.exe for Windows applications, *.hex for microcontrollers) at the end of the linking procedure.

Loading

The programme file must then be loaded into the computer's memory before it can be executed. A loader is in charge of this. The loader is usually included in the executable file by the linker. When we launch the executable, it activates the loader, which loads the programme into memory and starts the operation.

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Conclusion 

C’s proximity to the hardware, portability, and resource utilization predictability make it excellent for low-level development of operating system kernels and embedded applications. Its adaptability, efficiency, and high performance make it a perfect choice for data manipulation tools with significant complexity. Many programming languages today are better than C for their intended purposes, but it does not mean they are superior to C in all areas. When it comes to performance, C is still unrivaled. We hope that this article was able to give you a thorough knowledge of  Use of the C language and how we can use it in our software development projects.

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About the Author

Ravikiran A SRavikiran A S

Ravikiran A S works with Simplilearn as a Research Analyst. He an enthusiastic geek always in the hunt to learn the latest technologies. He is proficient with Java Programming Language, Big Data, and powerful Big Data Frameworks like Apache Hadoop and Apache Spark.

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