C language Introduction

From Algol to Traditional C

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1. Algol (Algorithmic Language)

• Year: 1950s
• What is it: Algol was one of the earliest high-level programming languages. It was used mainly for mathematical and scientific computations.
• Importance: Algol laid the foundation for the structure and syntax of many modern programming languages.

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2. BCPL (Basic Combined Programming Language)

• Year: 1966
• Developer: Martin Richards
• What is it: BCPL was a simple and powerful language designed for system programming. It served as a foundation for the development of the C language.

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3. B Language

• Year: 1969
• Developer: Ken Thompson
• What is it: The B language was derived from BCPL. It was developed for the UNIX operating system. While useful, B was limited in features.

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4. C Language

• Year: 1972
• Developer: Dennis Ritchie
• What is it:
• C was developed at Bell Labs.
• The goal was to create a powerful low-level language for system programming, particularly for the UNIX operating system.
• It evolved from the B language and added new features like data types, functions, etc.
• C made programming more efficient, powerful, and portable.

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5. Traditional C

• Year: 1978
• Famous Book: The C Programming Language by Dennis Ritchie and Brian Kernighan
• What is it:
• This book provided the first comprehensive explanation of the C language.
• It’s often referred to as the "Kernighan and Ritchie" book.
• This version of C is known as ‘Traditional C’ or ‘K&R C’.
• It was the first stable and widely accepted standard of the C language.

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Key Contributors in the Development of C Language

Name	Contribution
Dennis Ritchie	Inventor of the C language; co-developer of UNIX OS.
Ken Thompson	Creator of B language; co-developer of UNIX OS.
Martin Richards	Developer of BCPL, which influenced C’s development.
Brian Kernighan	Co-author of the famous C book; helped spread the language.

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In Summary

• Algol → The base language that influenced modern languages.
• BCPL → A simple system-level programming language.
• B Language → A modified version of BCPL, created for UNIX.
• C Language → Developed by Dennis Ritchie; powerful, portable, and efficient.
• Traditional C → The first standard version of C, documented in 1978.

History of C Language

• The C language was developed by Dennis Ritchie in 1972 at Bell Labs (USA).
• It was created for the development of the Unix Operating System.
• C was developed from the B language, which was an earlier programming language.
• The popularity of C grew rapidly, and it is still used today to develop many systems and applications.

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Advantages of C Language

1. Fast and Efficient:
   C is a very fast language and uses minimal system resources.
2. Best for System Programming:
   Ideal for creating operating systems, drivers, etc.
3. Structured Programming:
   Helps organize code into functions, making programming simpler.
4. Strong Foundation for Other Languages:
   Learning C makes it easier to learn other languages like C++, Java, and Python.
5. Close to Hardware:
   Allows direct control over memory and hardware.

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Disadvantages of C Language

1. Not Object-Oriented:
   It does not support the concept of classes and objects.
2. Less Secure:
   Manual memory management can lead to errors and vulnerabilities.
3. No Built-in GUI Support:
   Requires additional libraries for graphics or user interface.
4. Error Handling is Difficult:
   Compared to other languages, detecting and handling errors is more challenging.

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Procedure Oriented Programming (POP)

In procedure-oriented programming, a program is divided into small functions or procedures. It focuses more on process or logic than on data.

Features:

• Data and functions are kept separate.
• Code reuse is difficult.
• Traditional way of programming.
• Examples: C, Pascal, FORTRAN, etc.

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Object Oriented Programming (OOP)

In object-oriented programming, the program is structured around objects. It organizes data and the functions that operate on that data into classes.

Features:

• Combines data and functions into a single object.
• Easier code reusability and scalability.
• Supports modern features like encapsulation and inheritance.
• Examples: C++, Java, Python, C#, etc.

Difference between POP and OOP

Feature	Procedure-Oriented Programming (POP)	Object-Oriented Programming (OOP)
1. Basis	Based on Process	Based on Object
2. Data Security	Data is not secure	Data is secure (Encapsulation)
3. Structure	Functions and data are separate	Functions and data are together in objects
4. Reusability	Code reusability is difficult	Code reusability is easy
5. Examples	C, Pascal, FORTRAN	C++, Java, Python
6. Complexity Management	Difficult to manage large programs	Easy to manage large programs
7. Development Approach	Traditional	Modern

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1. Character Set in C Language

To write programs in the C language, a specific set of characters is used. This set is called the Character Set, and it consists of the following types:

(i) Letters:

• Small Letters: a to z
• Capital Letters: A to Z

(ii) Digits:

• 0 to 9

(iii) Special Characters:

Special Character	Name in English	Name in Hindi
!	Exclamation mark	विस्मयादिबोधक चिन्ह
@	At symbol	ऐट चिन्ह
#	Hash / Number sign	हैश / संख्या चिन्ह
$	Dollar sign	डॉलर चिन्ह
%	Percent sign	प्रतिशत चिन्ह
^	Caret	कैरेट (घात के लिए)
&	Ampersand	एंड / संयोजन चिन्ह
*	Asterisk	तारक चिन्ह / गुणा चिन्ह
(	Left parenthesis	बाँया कोष्ठक (ब्रैकेट)
)	Right parenthesis	दायाँ कोष्ठक (ब्रैकेट)
-	Hyphen / Minus	ऋण चिन्ह / माइनस
_	Underscore	अधोरेखा
=	Equal sign	समानता चिन्ह
+	Plus sign	जोड़ चिन्ह / प्लस
{	Left curly brace	बाँया घुंघराला ब्रैकेट
}	Right curly brace	दायाँ घुंघराला ब्रैकेट
[	Left square bracket	बाँया वर्ग कोष्ठक
]	Right square bracket	दायाँ वर्ग कोष्ठक
:	Colon	कोलन
;	Semicolon	अर्धविराम
"	Double quote	डबल कोट्स
'	Single quote	सिंगल कोट्स
<	Less than	से कम
>	Greater than	से अधिक
,	Comma	अल्पविराम
.	Period / Dot	पूर्णविराम / बिंदु
?	Question mark	प्रश्नवाचक चिन्ह
/	Forward slash	स्लैश / भाग चिन्ह
\	Backslash	बैकस्लैश
`	Backtick	वक्र उच्चारण चिन्ह (used rarely)
`	`	Vertical bar / Pipe
~	Tilde	टिल्ड (~)

(iv) White Spaces:

• Space
• Tab
• New Line (Enter)

·        Keywords

·        Definition:
Keywords are reserved words that have special meanings in the C language and are used for specific purposes. They cannot be used as variable or function names.

·        List of 32 Major Keywords in C:

·        cpp

·        CopyEdit

·        auto        break       case        char 

·        const       continue    default     do 

·        double      else        enum        extern 

·        float       for         goto        if 

·        int         long        register    return 

·        short       signed      sizeof      static 

·        struct      switch      typedef     union 

·        unsigned    void        volatile    while 

·       

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·        Identifier

·        In C language, an Identifier is the name used to identify variables, functions, arrays, structures, etc.

·        Rules for Writing Identifiers in C:

S.No.	Rule	Explanation
1	Only letters (A-Z, a-z), digits (0-9), and the underscore (_) symbol can be used.	However, the name must not begin with a digit.
2	The identifier must start with a letter or underscore (_) only.	Example: _count, name1 are valid; 1name is invalid.
3	C keywords cannot be used as identifiers.	For example: int, return, while cannot be used as names.
4	Identifiers in C are case-sensitive.	Marks and marks are considered different.
5	The name of an identifier should be meaningful and clear.	Example: totalMarks is better than tm.
6	The maximum length of an identifier depends on the C compiler.

DATA TYPES:

1. Primary (Fundamental) Data Types (for 32-bit systems)

Data Type	Value Range
char	-128 to 127
unsigned char	0 to 255
int	-2,14,74,83,648 to 2,14,74,83,647
unsigned int	0 to 4,29,49,67,295
short int	-32,768 to 32,767
long int	Approximately -2 billion to +2 billion
float	Accuracy up to approximately 6 decimal digits
double	Accuracy up to approximately 15 decimal digits

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Key Notes:

1. The char type is actually an integer type used to store the ASCII values of characters.
2. short, int, long, and long long are all used for integer values, but with different ranges.
3. The unsigned type does not allow negative values.
4. float, double, and long double are used to store decimal (floating-point) values.

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2. User-Defined Data Types

These are defined by the programmer:

• struct (Structure)
• union (Union)
• enum (Enumeration)
• typedef (Used to create new type names)

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3. Derived Data Types

These are created from fundamental types:

• Array: A group of elements of the same type — e.g., int arr[5];
• Pointer: Stores the address of a variable — e.g., int *ptr;
• Function: Returns a value — e.g., int sum(int a, int b);
• Structure/Union: User-defined data types

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Operator

An operator is a symbol that performs an operation on variables or values.

Example:

int a = 5 + 3;

Here, + is an operator that adds 5 and 3.

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Main Types of Operators in C Language:

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1. Arithmetic Operators

Operator	Meaning	Example (a = 10, b = 5)	Output
+	Addition	a + b	15
-	Subtraction	a - b	5
*	Multiplication	a * b	50
/	Division	a / b	2
%	Modulus (Remainder)	a % b	0

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2. Relational Operators

These operators compare two values and return true (1) or false (0).

Operator	Meaning	Example (a = 10, b = 5)	Output
==	Equal to?	a == b	0
!=	Not equal to?	a != b	1
>	Greater than?	a > b	1
<	Less than?	a < b	0
>=	Greater or equal?	a >= b	1
<=	Less or equal?	a <= b	0

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3. Logical Operators

Used to combine or test conditions:

Operator	Name	Meaning
&&	AND	True only if both conditions are true
`		`
!	NOT	Reverses the result: true becomes false, and vice versa

Example:

 (a > 5 && b < 10)  // returns true (1)

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4. Assignment Operators

Operator	Meaning	Example
=	Assign value	a = 5
+=	Add and assign	a += 3 → a = a + 3
-=	Subtract and assign	a -= 2 → a = a - 2
*=	Multiply and assign	a *= 4
/=	Divide and assign	a /= 2

5. Increment & Decrement Operators

Operator	Meaning	Example
++	Increment by 1	a++ or ++a
--	Decrement by 1	a-- or --a

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6. Bitwise Operators

Bitwise operators in C perform operations on the binary bits of numbers. They work bit-by-bit, not on the entire number at once.

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1. & (Bitwise AND)

Compares bits of both operands and returns 1 only if both bits are 1.

Example:

int a = 5;    // Binary: 0101 

int b = 3;    // Binary: 0011 

int c = a & b;  // Result: 0001 (Decimal: 1)

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2. | (Bitwise OR)

Returns 1 if any one bit is 1.

Example:

int a = 5;    // Binary: 0101 

int b = 3;    // Binary: 0011 

int c = a | b;  // Result: 0111 (Decimal: 7)

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3. ^ (Bitwise XOR)

Returns 1 if the bits are different (one is 0 and the other is 1).

Example:

int a = 5;    // Binary: 0101 

int b = 3;    // Binary: 0011 

int c = a ^ b;  // Result: 0110 (Decimal: 6)

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4. ~ (Bitwise NOT)

A unary operator that inverts each bit (0 becomes 1, and 1 becomes 0).

Note: The result is shown in 2's complement form, so it may appear as a negative number for signed integers.

Example:

int a = 5;     // Binary: 0101 

int c = ~a;    // Result: 1010 → Output: -6 (in 2's complement)

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5. << (Left Shift)

Shifts all bits to the left, and fills 0s on the right.

Example:

int a = 5;     // Binary: 0101 

int c = a << 1;  // Result: 1010 (Decimal: 10)

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6. >> (Right Shift)

Shifts all bits to the right, and the leftmost bit is filled with the sign bit.

Example:

int a = 5;     // Binary: 0101 

int c = a >> 1;  // Result: 0010 (Decimal: 2)

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Conditional Operator (Ternary Operator)

The Conditional Operator in C is also called the Ternary Operator because it works with three operands. It provides a shortcut for if-else statements.

Syntax:

condition ? expression_if_true : expression_if_false;

• condition → A valid logical or comparison expression.
• If the condition is true, expression_if_true is executed.
• If the condition is false, expression_if_false is executed.

Example:

#include <stdio.h>

 

int main() {

    int a = 10, b = 20;

    int max;

 

    max = (a > b) ? a : b;

 

    printf("The larger value is: %d\n", max);

    return 0;

}

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sizeof Operator

The sizeof operator is a unary compile-time operator that tells the memory size (in bytes) of a data type or variable.

Syntax:

sizeof(type)

or

sizeof(variable)

It tells the compiler how much memory a data type or variable occupies.

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Example:

#include <stdio.h>

 

int main() {

    int a;

    float b;

    char c;

    double d;

 

    printf("Size of int: %lu bytes\n", sizeof(a));

    printf("Size of float: %lu bytes\n", sizeof(b));

    printf("Size of char: %lu bytes\n", sizeof(c));

    printf("Size of double: %lu bytes\n", sizeof(d));

 

    return 0;

}

Note:

• %lu is used for unsigned long because sizeof returns a value of type size_t, which is an unsigned integer.

Definition:

A statement is an instruction that the compiler executes.
A C program is made up of multiple statements, and each statement performs a specific task.
Every C statement ends with a semicolon (;).

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 Types of Statements in C:

1. Expression Statement

• Executes an expression.
• Example:

a = b + 5;

i++;

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2. Declaration Statement

• Declares a variable or function.
• Example:

int x;

float pi;

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3. Compound Statement (Block)

• A group of multiple statements enclosed in curly braces {}.
• Example:

{

    int a = 10;

    a = a + 5;

    printf("%d", a);

}

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4. Control Flow Statements

• These statements control the flow of the program.
• Sub-types include:
• Selection statements → if, if-else, switch
• Looping statements → for, while, do-while
• Jump statements → break, continue, goto, return

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5. Null Statement

• Just a semicolon ; — does nothing.
• Example:

;

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Example Program:

#include <stdio.h>

 

int main() {

    int a = 10;              // Declaration + Expression Statement

    if (a > 5) {             // Selection Statement

        printf("a is big");  // Expression Statement

    }

    return 0;                // Jump Statement

}