C Language: Basics Guide For Beginners (PDF)

C Language Basics Information For Beginners

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Here, I will provide you all the basic information about the C language.

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Introduction Of C Language

C is a high-level computer programming language.

It is also known as:

  • Mother programming language
  • System programming language
  • Mid-level programming language
  • Procedure-oriented programming language
  • Structured programming language

Usually, this language is designed to be compiled with a relatively simple compiler.

It provides low-level access to memory.

So, it requires minimum runtime support to process instructions.

If you learn this language, another programming language is easy to understand for you.

History Of C Language

It is interesting to know the history of the C language.

Here, I discuss a brief history of the c language.

Dennis Ritchie

It was originally invented by Dennis Ritchie in 1972 at AT & T’s Bell Laboratory in the USA.

It was primarily developed to writing UNIX operating system.

Gradually, it becomes a very popular programming language in the worldwide.

It has been standardized by the American National Standards Institute (ANSI) since 1989 and subsequently by the International Organization for Standardization (ISO).

Timeline of C language development

Version NameYearDeveloper
C1972Dennis Ritchie
K&R C1978Brian Kernighan & Dennis Ritchie
ANSI C1989ANSI Committee
ISO C1990ISO Committee
C991999Standardization Committee
C112011Standardization Committee
C182017/2018Standardization Committee

Features Of C Language

There are different types of features are available in the C language.

All the features are not possible to mention in one article.

Although, some of the key features are mentioned here:

  • Fast and Efficient
  • Easy to Extend
  • Procedural Language
  • Simple and clean style
  • Middle-Level Language
  • Low-level access to memory
  • Libraries with rich Functions
  • Rich set of built-in Operators
  • A simple set of keywords
  • Support memory management
Features Of C Language

These features make C language suitable for system programs like an operating system or compiler development.

Later programming languages have borrowed syntaxes and features directly or indirectly from C language.

Java, PHP, JavaScript, and many other programming languages are mainly based on C language.

Note: C++ is almost a superset of C (very few programs can be compiled with C, but not with C++).

Data Types

Each variable contains a specific data type.

Data types are used to define the data storage format.

Each data type requires different amounts of memory space and has some specific features.

There are mainly 4 data types that are mostly used in c programming.

Those are described here.

  • int: It is used to store an integer type value (numbers).
  • char: It stores a single character (alphabets).
  • float: It is used to store decimal numbers (floating-point value) with single precision.
  • double: It is also used to store decimal numbers (floating-point value) with double precision.

An int is signed by default.

It means it can represent both positive and negative values.

On the other hand, an unsigned int can never be negative.

All data types are listed here.

Data TypeMemory (Bytes)RangeFormat specifier
short int2-32768 to 32767%hd
unsigned short int20 to 65535%hu
unsigned int40 to 4294967295%u
int4-2147483648 to 2147483647%d
long int8-2147483648 to 2147483647%ld
unsigned long int80 to 4294967295%lu
long long int8-(2^63) to (2^63)-1%lld
unsigned long long int80 to 18446744073709551615%llu
signed char1-128 to 127%c
unsigned char10 to 255%c
long double16%Lf

You can also use the sizeof() operator to check the size of any variable.


A variable is a simple word or letter that allocates some space in memory.

Basically, a variable used to store some different types of data.

Different types of variables require different amounts of memory and have some specific set of operations that can be applied to them.

/*variable declaration*/
int a;
char b;
float c;

Rules For Defining Variables

  1. A variable can have any alphabet, digit, and underscore.
  2. A variable name must start only with the alphabet, and underscore. It can’t start with a digit.
  3. No space is allowed within the variable name.
  4. A variable name can not be any reserved word or keyword. (e.g. int, void, etc.)


An array is a data structure that contains the same types of data items.

A variable can carry only one data item at a time.

If you want to store multiple data items in a data type, you need to use an array.

You can not initialize an array with more elements than the specified size.

The specified size is declared to the left of the variable between the third brackets.

1D array in c

A one-dimensional array is like a row list.

On the other hand, a two-dimensional (2D) array is like a table.

Arrays consist of contiguous memory locations.

Array Declaration

1. Array declaration by specifying the size

int a[5];

2. Array declaration by initializing the elements

int a[] = { 10, 20, 30, 40 };

3. Array declaration by specifying the size and initializing the elements

int arr[5] = { 10, 20, 30, 40 };

Note: You can use While or For loops to add values in the variables.


A pointer is a variable that stores the address of another variable.

For example, an integer variable stores an integer value, however an integer pointer stores the address of an integer variable.

We use the unary operator & (ampersand) that returns the address of a variable.

#include <stdio.h> 
int main() 
int x; 	
printf("%p", &x); 	
return 0; 

Here, &x print the address of variable x.


Keywords are specific reserved words in C which attached with a specific feature.

The list of keywords includes almost all the words that can help us to use the functionality of the C language.

C does not contain very large number of keywords.

However, there are 32 keywords are available in C98 language.


C99 reserved five more keywords.


C11 reserved seven more keywords.


Most of the recently reserved words begin with an underscore followed by a capital letter.

Because identifiers of that form were previously reserved by the C standard for use only by implementations.


C supports a rich set of operators, which are different types of symbols.

Each operator performs a specific operation with a variable.

All operators are listed in the following table.

Operator NameOperator Symbol
Arithmetic+, -, *, /, %
augmented assignment+=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=
bitwise logic~, &, |, ^
bitwise shifts<<, >>
boolean logic!, &&, ||
conditional evaluation? :
equality testing==, !=
calling functions( )
increment and decrement++, —
member selection., ->
object sizesizeof
order relations<, <=, >, >=
reference and dereference&, *, [ ]
subexpression grouping( )
type conversion(typename)

These operators tell the compiler to perform specific mathematical or logical operations.

Memory Management

The most important function of a programming language is to provide facilities for managing memory and objects that are stored in memory.

Executing C program

C language provides 3 unique ways to allocate memory for objects.

Static Memory Allocation

This is an allocation technique that allocates a fixed amount of memory during compile time.

Dynamic Memory Allocation

This is also an allocation technique that manages system memory at runtime.

Automatic Memory Allocation

When you declare an automatic variable (such as a function argument or a local variable), then it happens.


Library functions are inbuilt functions in C language that are grouped together in common files. This file is called the C standard library.

Each library provides specific functions to perform specific operations.

We can use these library functions to get the pre-defined output instead of writing your own huge complex code to get those outputs.

All C standard library functions are declared in header files which are saved as filename.h.

We are including the library in the header files in our C program.


The command allow to use of the functions that are declared in the header files.

Basic Structure Of C Program

A set of rules is defined for the C programs that are called protocols.

The protocols help us to design the basic structure of a program.

Here, I mentioned the basic structure of a C program.

  • Documentation section
  • Link section
  • Definition section
  • Global declaration section
  • Main function section
  • Sub-program section

All C programmers must follow the protocols when writing any program.

Let’s discuss all the basic structure sections of a C program.

Documentation Section

The documentation section is a part of the program where the programmers provide the details about the program.

In this section programmers usually give the name of the program and the details related to the program.

This code gives an overview of the program.

//program name
/*This is a
C Program*/

Link Section

This section is used to declare all the header files that will be used in the program.

It tells the compiler to link the header files to the system library.


Definition Section

In this section, we can define different types of constants.

The keyword define is used to define a constant value in this part.

#define PI=3.14

Global Declaration Section

All the global variables are declared in this section.

User-defined functions are also declared in this section of the code.

int a,b,c;

Main Function Section

Every C-programs must have the main function.

The main function contains 2 parts.

1. Declaration Part: All the variables are declared in this part.

2. Execution Part: This part starts with the curly brackets and ends with the curly close bracket.

Both the declaration and the execution part are writing inside the curly braces.

int main()
int a=5;
printf(" %d", a);
return 0;

Sub-program Section

All user-defined functions are defined in this section.

int add(int a, int b)
return a+b;
Structure of c program

Hello World C Program

This is the source code of a basic “Hello World” Program.

int main()
/*First basic C Program*/
printf("Hello World.");
return 0;

After compiling the source code the output will be the following:


Hello World.

Explanation of “Hello World” C Program

Here, I explained each line of the “Hello World” C program.

#include <stdio.h>

This is a preprocessor command that includes the input header file from the C library before compiling a program.

int main()

This is the main function of executing any C program begins.


It represents the beginning of the main program.

/*First basic C Program*/

If any words exist inside the command /* and */ in any C program that won’t be considered for compilation and execution. This is also called a comment line.

printf(“Hello World.“);

The printf command displays the words in the quote on the screen.


This function is used to hold the output screen and wait until the user gives any type of input. So that we are able to see the output on the screen.

return 0;

Here, the return is a keyword that is used to return some value from a function.

The main function returns an integer value, therefore here we are returning 0.

It means our program has been run successfully and we terminate our main function with this return statement.


It represents the ending of the main program.

Create a C Program

Are you want to create and execute a C programs yourself?

Then you need to follow the instructions:

  1. At first, you need to install a C supported IDE (Integrated Development Environment) on your computer.
  2. Once the IDE is installed on your computer, you can open and create a C program.

If you don’t want to install the IDE on your computer, you can use an online compiler or IDE.

The good thing about the online compiler is it can compile C, C++, C#, Java, and many other programming languages.

We also provide some links to the online and offline IDE in this article that can help you to create and execute your C program easily.

Best IDE For C

Best IDE for C

You can create and edit C programs with any code editor or even a general editor.

Yet, it is very important to choose the best IDE for beginners.

If the IDE is integrated with the C compiler, the process of creating and compiling the C program will be easier.

Anyway, we collect some best IDE for c program that can help you to write and execute any c program easily.

Here are some collection,

Run C Program Online

Run C Program On Android Phone

Run C Program On Windows

Run C Program In Mac OS

Run C Program In Linux

Choose the best IDE that makes you comfortable to create and edit the C program.

Thus, your programming skills will increase and you will be able to create any program within a few minutes.

Advantages Of C Language

  • It is one of the most useful programming languages when the system requires quick and direct access to the hardware.
  • C is the most commonly used system with limited resources (such as memory).
  • Where performance is the most important attribute, C is the best choice for programmers.

Disadvantages Of C Language

  • C does not support OOP (Object-oriented programming) concepts, that’s why C++ is developed.
  • There is no runtime checking ability in the C language. It only does compile-time checking.
  • It does not support the concept of the namespace. We cannot declare two variables of the same name without namespace.
  • It does not have the concept of constructor and destructor.

Uses Of C Language

There are different types of uses of C language in programming.

Some uses are the following:

  • C mainly used to develop system software, operating systems, BIOS, Embedded Systems, Real-time systems.
  • To develop application software like databases (MySQL) and 3D software (Autodesk Maya).
  • Used to create graphical related applications like computers and mobile games.
  • To evaluate any types of logical and mathematical equations using c language.
  • UNIX kernel is completely made in C Language.
  • The language is used to design different language compilers.


The C language doesn’t seem to have an expiration date.

It has a closeness to the hardware, great portability, and deterministic usage of resources.

For these features, it is the ideal programming language for low-level development of things like operating system kernels and embedded software.

Its good performance, efficiency, and versatility make it an excellent choice to develop highly complex data manipulation software like MySQL, 3D animation, and more.

C is still unsurpassed where performance is the main priority.

I hope now you know all the basic information about the C language.

Now it’s your turn.

What do you think about C Language?

Share your thoughts in the comment box.

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