History

- **How**:
	- Developed by **Dennis Ritchie** in the early 1970s at **Bell Labs**.
	- Designed as an evolution of the B programming language, with the goal of providing more control over hardware and efficient system programming.
	- Became the foundation for many modern programming languages and operating systems.
	- Evolved through versions, with the ANSI C standard (C89) and the C99 standard being notable milestones.
	-
- **Who**:
	- **Dennis Ritchie**, a computer scientist, is the creator of C.
	- **Bell Labs**, the research lab at AT&T, where C was first developed.
	-
- **Why**:
	- To create a portable, efficient language that could be used for system programming and writing operating systems.
	- To provide low-level access to memory and hardware while maintaining readability and simplicity.
	- To enable the development of the **UNIX operating system**, which was one of its first major uses.

introduction

Advantages:

Performance and Control: C offers direct memory manipulation through pointers and manual memory management, making it highly efficient for system programming, embedded systems, and performance-critical applications. This level of control allows developers to fine-tune performance but requires careful handling.
Portability: C is platform-independent, with programs easily portable across different systems. It has been the foundation of many operating systems and compilers, ensuring that C code can run on almost any machine with minimal changes.
Simplicity and Efficiency: The language’s minimalistic syntax makes C easy to learn and use, focusing on low-level functionality and providing high efficiency in system-level applications. It’s often the language of choice for tasks like OS development and embedded systems.
Wide Use and Support: As one of the oldest and most widely used languages, C enjoys strong community support, vast resources, and a large library ecosystem, making it a dependable choice for many types of programming.
Low-Level System Programming: C is perfect for system-level programming (e.g., operating systems, device drivers) due to its ability to interact directly with hardware and manage system resources efficiently.

Disadvantages:

Manual Memory Management: Unlike modern languages with garbage collection, C requires developers to manually manage memory using malloc and free. This can lead to memory leaks or segmentation faults if not handled correctly.
No Object-Oriented Features: C is a procedural language, lacking native support for object-oriented programming concepts like classes, inheritance, and polymorphism, which makes it less suited for large, complex applications that benefit from these features.
Error Handling: C lacks built-in exception handling (e.g., try/catch), requiring manual checks (return codes, error flags) that can make error management cumbersome and more error-prone.
Complex Pointer Arithmetic: The heavy use of pointers in C, while offering power and flexibility, also introduces complexity. Improper pointer manipulation can result in hard-to-find bugs, such as buffer overflows or memory corruption.
Low-Level Nature: C’s focus on low-level operations means it’s less suitable for high-level tasks such as GUI development or applications requiring extensive built-in libraries and frameworks, which are easier to implement in higher-level languages like Python or Java.
Lack of Higher-Level Abstractions: While C is powerful, it lacks the advanced data structures and higher-level abstractions found in languages like C++ or Java, requiring more effort to implement features like dynamic arrays, complex data structures, or multithreading.

Notes

main() is the entry point of a C program.
printf("Hello World\n"); is used for printing output.

variables Types

char	character type
short	short integer
int		integer type
long	long integer
float	single-precision floating-point type
double	double-precision floating-point type
void	no type

Data format example : ~

int number = 5;       // Integer
    float f = 0.95f;      // Floating point number
    double PI = 3.14159;  // Double precision floating point number
    char yes = 'Y';       // Character
    char s[] = "ME";      // String (array of characters)
    _Bool isRight = 1;    // Boolean (C99 and later, 1 for true, 0 for false)
    
    // Constants
    const float RATE = 0.8f;
 
    // Output the variables to check their values
    printf("Integer: %d\n", number);
    printf("Float: %.2f\n", f);
    printf("Double: %.5f\n", PI);
    printf("Char: %c\n", yes);
    printf("String: %s\n", s);
    printf("Boolean: %d\n", isRight);
    printf("Constant RATE: %.2f\n", RATE);

Primitive Data Types

Data Types in Details : ~

Data Types			Size 			Range / Description
char				1 byte			−128 ~ 127	single character/alphanumeric/ASCII
signed char			1 byte			−128 ~ 127	-
unsigned char		1 byte		   	   0 ~ 255	-
int					2 to 4 bytes −32,768 ~ 32,767	store integers
signed int			2 bytes	−32,	 768 ~ 32,767	
unsigned int		2 bytes			   0 ~ 65,535	
short int			2 bytes		 −32,768 ~ 32,767	
signed short int 	2 bytes		 −32,768 ~ 32,767	
unsigned short int	2 bytes			   0 ~ 65,535	
long int			4 bytes		 -2,147,483,648 ~ 2,147,483,647	
signed long int		4 bytes	-2,147,483,648 ~ 2,147,483,647	
unsigned long int	4 bytes			   0 ~ 4,294,967,295	
float				4 bytes		 3.4E-38 ~ 3.4E+38	
double				8 bytes		1.7E-308 ~ 1.7E+308	
long double			10 bytes   3.4E-4932 ~ 1.1E+4932

Basic format specifiers : ~

%d or %i				int integer
%f						float single-precision decimal type
%lf						double high precision floating point data or number
%c						char character
%s						for strings strings
 
-----------------------------------------------------------------------------
 
Octal				%ho			%o			%lo
Decimal				%hd			%d			%ld
Hexadecimal			%hx /%hX	%x /%X		%lx /%lX

User input string

// create a string
char firstName[30];
// Ask the user to enter some text
printf("Enter your name: \n");
// get and save the text
scanf("%s", &firstName);
// output text
printf("Hello %s.", firstName);

Comments

// this is a comment
printf("Hello World!"); // Can comment anywhere in file
 
/*Multi-line comment, print Hello World!
to the screen, it's awesome */

Condition

int time = 20;
if (time < 18) {
  printf("Goodbye!");
} else {
  printf("Good evening!");
}
// Output -> "Good evening!"
int time = 22;
if (time < 10) {
  printf("Good morning!");
} else if (time < 20) {
  printf("Goodbye!");
} else {
  printf("Good evening!");
}
// Output -> "Good evening!"

C Important Tags

Control the number of spaces

int a1 = 20, a2 = 345, a3 = 700;
int b1 = 56720, b2 = 9999, b3 = 20098;
int c1 = 233, c2 = 205, c3 = 1;
int d1 = 34, d2 = 0, d3 = 23;
 
printf("%-9d %-9d %-9d\n", a1, a2, a3);
printf("%-9d %-9d %-9d\n", b1, b2, b3);
printf("%-9d %-9d %-9d\n", c1, c2, c3);
printf("%-9d %-9d %-9d\n", d1, d2, d3);
 
--------------------------------------------------
20        345       700      
56720     9999      20098    
233       205       1        
34        0         23

Strings

char greetings[] = "Hello World!";
printf("%s", greetings);
access string
 
 
char greetings[] = "Hello World!";
printf("%c", greetings[0]);
modify string
 
 
char greetings[] = "Hello World!";
greetings[0] = 'J';
 
printf("%s", greetings);
// prints "Jello World!"
Another way to create a string
 
 
char greetings[] = {'H','e','l','l','\0'};
 
printf("%s", greetings);
// print "Hell!"
Creating String using character pointer (String Literals)
 
 
char *greetings = "Hello";
printf("%s", greetings);
// print "Hello!"

Switch

int day = 4;
 
switch (day) {
  case 3: printf("Wednesday"); break;
  case 4: printf("Thursday"); break;
  default:
    printf("Weekend!");
}
// output -> "Thursday" (day 4)

pointer variable

int myAge = 43; // an int variable
int*ptr = &myAge; // pointer variable named ptr, used to store the address of myAge
 
printf("%d\n", myAge); // print the value of myAge (43)
 
printf("%p\n", \&myAge); // output the memory address of myAge (0x7ffe5367e044)
printf("%p\n", ptr); // use the pointer (0x7ffe5367e044) to output the memory address of myAge
 
 
This will Show The Diffrance
 
int myAge = 43; // variable declaration
int*ptr = &myAge; // pointer declaration
 
// Reference: output myAge with a pointer
// memory address (0x7ffe5367e044)
printf("%p\n", ptr);
// dereference: output the value of myAge with a pointer (43)
printf("%d\n", *ptr);

Operators

Arithmetic Operators

int myNum = 100 + 50;
int sum1 = 100 + 50; // 150 (100 + 50)
int sum2 = sum1 + 250; // 400 (150 + 250)
int sum3 = sum2 + sum2; // 800 (400 + 400)

Assignment operator

x = 5			x = 5
x += 3			x = x + 3
x -= 3			x = x - 3
x *= 3			x = x * 3
x /= 3			x = x / 3
x %= 3			x = x % 3
x &= 3			x = x & 3
x |= 3			x = x | 3
x ^= 3			x = x ^ 3
x >>= 3			x = x >> 3
x <<= 3			x = x << 3

Comparison Operators

// Demo
 
int x = 5;
int y = 3;
 
printf("%d", x > y);
// returns 1 (true) because 5 is greater than 3
 
---------------------------------------------------------------------------------
==	equals	x == y
!=	not equal to	x != y
>	greater than	x > y
<	less than	x < y
>=	greater than or equal to	x >= y
<=	less than or equal to	x <= y

Logical Operators

&&	and logical	returns true if both statements are true		x < 5 && x < 10
||	or logical	returns true if one of the statements is true	x < 5 || x < 4
!	not logical	Invert result, return false if true				!(x < 5 && x < 10)

Bitwise operators

&				Bitwise AND operation, "AND" operation by binary digits				(A & B) will get 12 which is 0000 1100
|				Bitwise OR operator, "or" operation by binary digit					(A | B) will get 61 which is 0011 1101
^				XOR operator, perform "XOR" operation by binary digits				(A ^ B) will get 49 which is 0011 0001
~				Inversion operator, perform "inversion" operation by binary bit		(~A) will get -61 which is 1100 0011
<<				binary left shift operator											A << 2 will get 240 which is 1111 0000
>>				binary right shift operator											A >> 2 will get 15 which is 0000 1111

C Preprocessor

Preprocessor Directives

#define		define a macro
#include	include a source code file
#undef		undefined macro
#ifdef		Returns true if the macro is defined
#ifndef		Returns true if the macro is not defined
#if			Compile the following code if the given condition is true
#else		Alternative to #if
#elif		If the #if condition is false, the current condition is true
#endif		End a #if...#else conditional compilation block
#error		Print an error message when standard error is encountered
#pragma		Issue special commands to the compiler using the standardized method
 
---------------------------------------------------------------------------------
  
// replace all MAX_ARRAY_LENGTH with 20
#define MAX_ARRAY_LENGTH 20
// Get stdio.h from the system library
#include <stdio.h>
// Get myheader.h in the local directory
#include "myheader.h"
#undef FILE_SIZE
#define FILE_SIZE 42 // undefine and define to 42

Predefined macros

__DATE__	The current date, a character constant in the format "MMM DD YYYY"
__TIME__	The current time, a character constant in the format "HH:MM:SS"
__FILE__	This will contain the current filename, a string constant
__LINE__	This will contain the current line number, a decimal constant
__STDC__	Defined as 1 when the compiler compiles against the ANSI standard
 
-----------------------------------------------------------------------------
 
// Example
#include <stdio.h>
 
int main() {
  printf("File :%s\n", __FILE__);
  printf("Date :%s\n", __DATE__);
  printf("Time :%s\n", __TIME__);
  printf("Line :%d\n", __LINE__);
  printf("ANSI :%d\n", __STDC__);
}

Macro continuation operator ()

#define message_for(a, b) \
    printf(#a " and " #b ": We love you(@' 3 '@)!\n")

C Function

Function declaration and definition

int main(void) {
  printf("Hello World!");
 
  return 0;
}
The function consists of two parts
 
 
void myFunction() { // declaration declaration
  // function body (code to be executed) (definition)
}
Declaration declares the function name, return type and parameters (if any)
Definition function body (code to execute)
 
// function declaration
void myFunction();
// main method
int main() {
  myFunction(); // --> call the function
 
  return 0;
}
 
void myFunction() {// Function definition
  printf("Good evening!");
}

Call function

// create function
void myFunction() {
  printf("Good evening!");
}
 
int main() {
  myFunction(); // call the function
  myFunction(); // can be called multiple times
 
  return 0;
}
// Output -> "Good evening!"
// Output -> "Good evening!"

Function parameters

void myFunction(char name[]) {
  printf("Hello %s\n", name);
}
 
int main() {
  myFunction("Liam");
  myFunction("Jenny");
 
  return 0;
}
// Hello Liam
// Hello Jenny

Multiple parameters

void myFunction(char name[], int age) {
  printf("Hi %s, you are %d years old.\n",name,age);
}
int main() {
  myFunction("Liam", 3);
  myFunction("Jenny", 14);
 
  return 0;
}
// Hi Liam you are 3 years old.
// Hi Jenny you are 14 years old.

Return value

int myFunction(int x) {
  return 5 + x;
}
 
int main() {
  printf("Result: %d", myFunction(3));
  return 0;
}
// output 8 (5 + 3)
two parameters
 
 
int myFunction(int x, int y) {
  return x + y;
}
 
int main() {
  printf("Result: %d", myFunction(5, 3));
  // store the result in a variable
  int result = myFunction(5, 3);
  printf("Result = %d", result);
 
  return 0;
}
// result: 8 (5 + 3)
// result = 8 (5 + 3)

Recursive example

int sum(int k);
 
int main() {
  int result = sum(10);
  printf("%d", result);
 
  return 0;
}
 
int sum(int k) {
  if (k > 0) {
    return k + sum(k -1);
  } else {
    return 0;
  }
}

Mathematical functions

#include <math.h>
 
void main(void) {
  printf("%f", sqrt(16)); // square root
  printf("%f", ceil(1.4)); // round up (round)
  printf("%f", floor(1.4)); // round up (round)
  printf("%f", pow(4, 3)); // x(4) to the power of y(3)
}
abs(x) absolute value
acos(x) arc cosine value
asin(x) arc sine
atan(x) arc tangent
cbrt(x) cube root
cos(x) cosine
the value of exp(x) Ex
sin(x) the sine of x
tangent of tan(x) angle

Function parameters

void myFunction(char name[]) {
  printf("Hello %s\n", name);
}
 
int main() {
  myFunction("Liam");
  myFunction("Jenny");
 
  return 0;
}
// Hello Liam
// Hello Jenny

Multiple parameters

void myFunction(char name[], int age) {
  printf("Hi %s, you are %d years old.\n",name,age);
}
int main() {
  myFunction("Liam", 3);
  myFunction("Jenny", 14);
 
  return 0;
}
// Hi Liam you are 3 years old.
// Hi Jenny you are 14 years old.

Return value

int myFunction(int x) {
  return 5 + x;
}
 
int main() {
  printf("Result: %d", myFunction(3));
  return 0;
}
// output 8 (5 + 3)

Recursive example

int sum(int k);
 
int main() {
  int result = sum(10);
  printf("%d", result);
 
  return 0;
}
 
int sum(int k) {
  if (k > 0) {
    return k + sum(k -1);
  } else {
    return 0;
  }
}

Mathematical functions

#include <math.h>
 
void main(void) {
  printf("%f", sqrt(16)); // square root
  printf("%f", ceil(1.4)); // round up (round)
  printf("%f", floor(1.4)); // round up (round)
  printf("%f", pow(4, 3)); // x(4) to the power of y(3)
}
-------------------------------------------------------------------------
  abs(x) absolute value
acos(x) arc cosine value
asin(x) arc sine
atan(x) arc tangent
cbrt(x) cube root
cos(x) cosine
the value of exp(x) Ex
sin(x) the sine of x
tangent of tan(x) angle

Return value

int myFunction(int x) {
  return 5 + x;
}
 
int main() {
  printf("Result: %d", myFunction(3));
  return 0;
}
// output 8 (5 + 3)
---------------------------------------------------------
//  two parameters
 
int myFunction(int x, int y) {
  return x + y;
}
 
int main() {
  printf("Result: %d", myFunction(5, 3));
  // store the result in a variable
  int result = myFunction(5, 3);
  printf("Result = %d", result);
 
  return 0;
}
// result: 8 (5 + 3)
// result = 8 (5 + 3)

C Structures

Create structure

struct MyStructure { // structure declaration
  int myNum; // member (int variable)
  char myLetter; // member (char variable)
}; // end the structure with a semicolon
Create a struct variable called s1
 
struct myStructure {
  int myNum;
  char myLetter;
};
 
int main() {
  struct myStructure s1;
 
  return 0;
}

Strings in the structure

struct myStructure {
  int myNum;
  char myLetter;
  char myString[30]; // String
};
 
int main() {
  struct myStructure s1;
  strcpy(s1. myString, "Some text");
  // print value
  printf("my string: %s", s1.myString);
 
  return 0;
}

Accessing structure members

// create a structure called myStructure
struct myStructure {
  int myNum;
  char myLetter;
};
 
int main() {
  // Create a structure variable called myStructure called s1
  struct myStructure s1;
  // Assign values to the members of s1
  s1.myNum = 13;
  s1.myLetter = 'B';
 
  // Create a structure variable of myStructure called s2
  // and assign it a value
  struct myStructure s2 = {13, 'B'};
  // print value
  printf("My number: %d\n", s1.myNum);
  printf("My letter: %c\n", s1.myLetter);
 
  return 0;
}`
 
--------------------------------------------------------------------------
// Create different structure variables
 
struct myStructure s1;
struct myStructure s2;
// Assign values to different structure variables
s1.myNum = 13;
s1.myLetter = 'B';
 
s2.myNum = 20;
s2.myLetter = 'C';

Copy structure

struct myStructure s1 = {
  13, 'B', "Some text"
};
 
struct myStructure s2;
s2 = s1;

Modify value

// Create a struct variable and assign it a value
struct myStructure s1 = {
  13, 'B'
};
// modify the value
s1.myNum = 30;
s1.myLetter = 'C';
// print value
printf("%d %c %s",
    s1.myNum,
    s1.myLetter);

file processing

File processing function

fopen()			open a new or existing file
fprintf()		write data to file
fscanf()		read data from a file
fputc()			write a character to file
fgetc()			read a character from a file
fclose()		close the file
fseek()			set the file pointer to the given position
fputw()			Write an integer to a file
fgetw()			read an integer from a file
ftell()			returns the current position
rewind()		set the file pointer to the beginning of the file

Open mode parameter

r		Open a text file in read mode, allowing the file to be read
w		Open a text file in write mode, allowing writing to the file
a		Open a text file in append mode
If 		the file does not exist, a new one will be created
r+		Open a text file in read-write mode, allowing reading and writing of the file
w+		Open a text file in read-write mode, allowing reading and writing of the file
a+		Open a text file in read-write mode, allowing reading and writing of the file
rb		Open a binary file in read mode
wb		Open binary file in write mode
ab		Open a binary file in append mode
rb+		open binary file in read-write mode
wb+		Open binary file in read-write mode
ab+		open binary file in read-write mode

Library & Frameworks

GLib - Core library for C with data structures, utilities, and threading.
GTK - GUI toolkit for creating graphical user interfaces.
libcurl - Library for transferring data with URLs (HTTP, FTP, etc.).
OpenSSL - Cryptography and SSL/TLS protocols.
SQLite - Lightweight, self-contained SQL database engine.
libxml2 - XML parsing and manipulation.
ncurses - Library for text-based interfaces and terminal handling.
SDL - Multimedia library for graphics, sound, and input handling in games.
pthread - POSIX threads library for multithreading support.
libevent - Event notification library for asynchronous I/O.
jansson - JSON library for encoding and decoding.
zlib - Data compression library.

More Learn

Explore the following links for valuable resources, communities, and tools to enhance your skills : -

C Programing Algorithms

Code Notes – Free Programming Reference by Vaibhav Rathod

Explorer

C

History

introduction

Advantages:

Disadvantages:

Notes

variables Types

Primitive Data Types

User input string

Comments

Condition

C Important Tags

pointer variable

Operators

Arithmetic Operators

Assignment operator

Comparison Operators

Logical Operators

Bitwise operators

C Preprocessor

Preprocessor Directives

Predefined macros

Macro continuation operator ()

C Function

Function declaration and definition

Call function

Function parameters

Multiple parameters

Return value

Recursive example

Mathematical functions

Function parameters

Multiple parameters

Return value

Recursive example

Mathematical functions

Return value

C Structures

Create structure

Strings in the structure

Accessing structure members

Copy structure

Modify value

file processing

File processing function

Open mode parameter

Library & Frameworks

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