C Language basics

Introduction to C

C is a general-purpose programming language developed in the early 1970s by Dennis Ritchie. C was designed to provide low-level access to memory while remaining portable across different systems. Because of this balance, C is widely used in operating systems, embedded systems, compilers, and performance-critical applications.An introduction to C language is often recommended as the first step for anyone serious about learning programming. Many popular languages such as C++, Java, and Python are influenced by C, making it an excellent starting point.

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Features of C Programming Language

The C programming language is popular because of its powerful features and wide range of applications. Understanding the features of C helps beginners appreciate why it is still widely used in software development today.Below are the main features of C, explained based on the highlighted points.

1. General Purpose and Portable

C is a general-purpose programming language, which means it can be used to develop a wide variety of applications such as operating systems, databases, and embedded systems.It is also portable, meaning a program written in C can run on different machines with little or no modification.

2. Procedural Programming Language

C follows a procedural programming approach. Programs are divided into functions, and each function performs a specific task.This makes C programs easy to understand, test, debug, and maintain, especially for large applications.

3. Low-Level Memory Access

One of the most powerful features of C is its ability to access memory directly using pointers.This low-level memory control makes C suitable for system programming, device drivers, and embedded systems where performance and memory efficiency are critical.

4. Fast Speed

C is a compiled language, which means programs are converted directly into machine code.Because of this, C programs execute very fast and use system resources efficiently, making them ideal for performance-critical applications.

5. Clean Syntax

The syntax of C is simple, clean, and easy to learn.It uses a limited number of keywords and a structured format, which helps beginners write clear and readable programs.

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Syntax of C Programming Language

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}

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Identifiers in C

In the C programming language, identifiers are the names used to identify variables, functions, arrays, and other user-defined elements in a program. Identifiers help the compiler and programmers distinguish one element from another.

Example:

int total;
float salary;
void calculateSum();

In the above examples, total, salary, and calculateSum are identifiers.

Rules for Naming Identifiers in C

To write valid identifiers in C, the following rules must be followed:

1. An identifier must start with a letter (a–z or A–Z) or an underscore (_).
2. It can contain letters, digits, and underscores.
3. It must not start with a digit.
4. No special characters such as @, #, $, or spaces are allowed.
5. Keywords of C cannot be used as identifiers.
6. Identifiers are case-sensitive (count and Count are different).

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Keywords in C

Keywords in C are special words recognized by the compiler. Each keyword has a fixed purpose and is part of the language syntax.

Example:

int number;

Here, int is a keyword.

List of Keywords in C

C has 32 standard keywords:

Rules for Using Keywords in C

1. Keywords cannot be used as identifiers
2. Keywords are written in lowercase
3. Each keyword has a predefined meaning
4. Keywords are case-sensit

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Variables in C

In the C programming language, a variable is a named memory location used to store data that can be changed during program execution. Variables allow programs to store, process, and manipulate data efficiently.

Example:

int age = 20;

Here, age is a variable that stores an integer value.

Declaration of Variables in C

Before using a variable in C, it must be declared with a data type.

Syntax:

data_type variable_name;

Example:

int number;
float price;
char grade;

Initialization of Variables in C

Initialization means assigning a value to a variable.

int count = 10;
float salary = 25000.50;
char letter = 'A';

Types of Variables in C

1. Local Variables

Declared inside a function and accessible only within that function.

void func() {
    int x = 5;
}

2. Global Variables

Declared outside all functions and accessible throughout the program.

int total;

3. Static Variables

Retain their value between function calls.

static int count = 0;

Data Types in C

Data types in C play a crucial role in program execution. They help:

• Allocate appropriate memory space
• Improve program performance
• Avoid logical and runtime errors
• Make code readable and maintainable

Understanding data types in C allows programmers to choose the right type for the right task.

Classification of Data Types in C

Data types in C are mainly divided into three categories:

1. Basic Data Types in C
2. Derived Data Types
3. User Defined Data Types

Each category of data types in C serves a specific purpose in program development.

Basic Data Types in C

Basic data types in C are the fundamental building blocks used to store simple values. These data types in C are predefined and widely used.

Common basic data types in C include:

• int – stores integer values
• float – stores decimal values
• double – stores double-precision floating-point values
• char – stores single characters

Example:

#include <stdio.h>
int main() {
    int age = 20;
    float marks = 85.5;
    char grade = 'A';

    printf("Age: %d\n", age);
    printf("Marks: %.1f\n", marks);
    printf("Grade: %c\n", grade);

    return 0;
}

OUTPUT

Age: 20
Marks: 85.5
Grade: A

These basic data types in C are essential for storing numeric and character data.

Derived Data Types in C

Derived data types are formed by using basic data types in C. These data types in C allow more complex data handling.

Examples of derived data types:

• Arrays
• Pointers
• Structures
• Unions

Derived data types in C help in storing multiple values and managing large amounts of data efficiently.

User Defined Data Types in C

User defined data types in C allow programmers to create their own data types according to program requirements. These data types in C improve code organization and reusability.

Common user defined data types include:

• struct
• union
• enum
• typedef

User defined data types in C are widely used in real-world applications to represent complex entities.