Programming:

• Sequence of instructions (precise) that we give to a computer to perform a task.

Why C?

• Java(android), C++, Python(AI, ML), JS(Website Building), PHP, etc.

• Every language has its role.

• Operating System => Android, Linux, Windows, Mac, ios => Written in C/C++ (Kernal => Heart of a OS)

• Scientific Computing Tools:- AI/ML {Tensorflow => core written in C/C++ by Google}, Weather forecasting, Biology

• Gaming S/W => C/C++ => Because they have to very fast.

• Device Drivers => C/C++

• Hardware/IoT Programming => C/C++ (Controlling Hardware)

  

  

Basic Input & Output:

```
#include<stdio.h>

int main()
{
    printf("Hello World");  //Print Formatted on STD O/P Device.
    return 0;
}
```

```
#include<stdio.h>

int main()
{
    char name[100];

    printf("Whats Your Name? ");
    scanf("%s", name);  //Scan Formatted from STD I/P Device.
    printf("\nHello, %s", name);

    return 0;
}
```

• Prime Number (Core) -> Password/Banking/LogIn => Encryption(Key Concept) => Cryptography
• Sending password in encrypted form from one computer to another computer.

Character Set:

• Set of character that are used in C

  • UpperCase Alphabets
  • LowerCase Alphabets
  • Digits
  • White Space -> New Line, Tabs
  • Special Character +,*,<,>,$,#,!

• There are two type of Character Set used generally:

  • ASCII (Older) => 0 to 255 [256 Numbers]

    

  • Unicode (Modern) => 1,114,112 Unique Characters

• C follows ASCII Character Set Standard Only.

  • 0 to 127 => Printable Characters
  • 128 to 255 => Non-Printable Characters

• Any Character Set ==> Converted (Nummeric form) ==> Binary Representation ==> RAM/DISK (store)

Keywords & Identifiers:

• 32 Keywords are predefined words in C that we cannot use, they have special meaning.

  auto	double	int	struct
  break	else	long	switch
  case	enum	register	typedef
  char	extern	return	union
  continue	for	signed	void
  do	if	static	while
  default	goto	sizeof	volatile
  const	float	short	unsigned

• Identifiers are the word that we use to make variable name function name and many other things.

• In General, Identifier is valid word in C.

• Rule for Identifier:

  • Alphabets, _(underscore), digits
  • First character => Alphabet
  • Not Keyword
  • Case - Sensitive
  • Length of Identifier => Compiler/Implementation
    • Older compiler => 8 character
    • ANSI C Standard => Most Compiler => 31 character

• Some Compilers: GCC, Visual Studio, Borland, Clang, intel, etc.

Data Types:

• Primary => void, char, int, float(Single precision real values), double(double precision real values)

• Qualifiers:

  • short, long
  • signed, unsigned

• Secondary => Arrays, Strings, Pointers, Structure, enumerator.

  Data Types	Range	Bytes	Format
  signed char	-128 to +127	1	%c
  unsigned char	0 to 255	1	%c
  short signed int	-32768 to +32767	2	%d
  short unsigned int	0 to 653535	2	%u
  signed int	-32768 to +32767	2	%d
  unsigned int	0 to 653535	2	%u
  long signed int	-2147483648 to +2147483647	4	%ld
  long unsigned int	0 to 4294967295	4	%lu
  float	-3.4e38 to +3.4e38	4	%f
  double	-1.7e308 to +1.7e308	8	%lf
  long double	-1.7e4932 to +1.7e4932	10	%Lf

• The size and ranges of int, short and long are compiler dependent, Sizes in above table are for 16-bit compiler.

Variables:

• All variables names is identifiers.
• Every variable should have a datatypes.
• Declaration: Stating that a variable exists. for e.g, int a;
• Always declare before using variable otherwise compiler will through a error.
• Typically, We should use camelCase to represent a variable name.
• Initialization: Storing some value during declaration. for e.g, int a = 19;

Constants:

• Do not change throughout of the program. for e.g, const int a = 5;

• Types of constant: char, string, integer, real-valued

  Data Types	Example
  int	int a = 10;
  char	char name = 'a'
  string	char name[10] = "avinash"
  real-valued	float: 1.2F or 1.2f, 1.2e5, long: 1.2L or 1.2l

• Decimal System: 0,1,2,3,4,5,6,7,8,9 => Base 10

  1	2	3
  x	x	x
  10^2	10^1	10^0
  100	+20	+3

  => 123(Decimal)

• Octal System: 0,1,2,3,4,5,6,7,8 => Base 8 => int a = 012;

  0	1	2
  -	x	x
  -	8^1	8^0
  -	8	+2

  => 10(Decimal)

• Hexa-Decimal System: 0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f => Base 16 => int a = 0x12;

  0	x	1	2
  -	-	x	x
  -	-	16^1	16^0
  -	-	16	+2

  => 18(Decimal)

• Symbolic Constant: #define PI 3.14 => Macro

Input Output:

• #include <stdio.h> => Including Header file where some of the key information of printf and scanf how they work is stored in stdio.h header file.

• Escape Sequence:

  

• scanf can take input multiple variables value in single line of code.

Input Output Formatting:

• Integers: scanf("%2d %3d", &a, &b); //Formatted Input

    a: read only first 2 digits
    b: read only first 3 digits
  
    Case 1: 6, 39 => a = 6 b = 39
    Case 2: 12, 123 => a = 12 b = 123
    Case 3: 123, 1234 => a = 12 b = 3
    Case 4: 12, 1234 => a = 12 b = 123
  

• Integers: printf("a = %4d, b = %3d", a, b); //Formatted Output

    a: print atmost(Minimum no. of digit) 4 digits
    b: print atmost(Minimum no. of digit) 3 digits
  
    Case 1: a = 12, b = 14 => a = _ _ _ _, b = _ _ _ _ => a = __12, b = _14
    Case 2: a = 12345, b = 123456 => a = 12345, b = 123456
  

• float: scanf("%3f %4f", &a, &b); //Formatted Input

    a: read only first 2 digits(Maximum no. of digits)
    b: read only first 3 digits(Maximum no. of digits)
  
    Case 1: 5, 5.9 => a = 5.0 b = 5.9
    Case 2: 5.1, 1.23 => a = 5.1 b = 1.23
    Case 3: 1.23, 4.5678 => a = 1.2 b = 3.0
  

• float: printf("a = %4.1f, b = %7.2f", a, b); //Formatted Output

  a: print atmost(Minimum no. of digit) 4 digits
  b: print atmost(Minimum no. of digit) 7 digits
  
  Case 1: a = 8.0, b = 5.9 => a = _ _ _ _, b = _ _ _ _ _ _ _=> a = _8.0, b = ___5.90
  Case 2: a = 15.231, b = 65.12345 => a = 15.2, b = __65.12
  

• Strings: char str[10] = "abcdef";

  • Input:

        Case 1: scanf("%s", str); => abcdef\0 -> str
        Case 2: scanf("%3s", str); => abc\0 -> str
    

  • Output:

        Case 1: printf("%3s", "abcdef"); -> abcdef
        Case 2: printf("%5s", "abcdef"); -> ___ab
        Case 3: printf("%.3s", "abcdef"); -> abc
        Case 4: printf("%8.3s", "abcdef"); -> _____abc
    

• Suppresssion Character:

  • scanf("%d%*d%d", &a, &b, &c); I/P: 25, 30, 35 => O/P: a = 25, b = 35, c = garbage value

  • variable c will suppressed so, nothing is stored

• getchar() & putchar()

  char c;
  printf("Enter a char: ");
  c = getchar(); //scanf("%c", &c);
  
  putchar(c); //printf("Value you entered : %c", c);
  

Operation & Expressions:

• Unary Operator: Operating on one data_type

• Binary Operator: Operating on two data_type(same or other)

  • NOTE: int divided by int result is also int
  • There is no any modulo operation in floating point number, No sense to get remainder in floating point number.

• Assigment Operator: for e.g, int x = 5;

• Increment / Decrement Operator

  Consider the following C Program:
  #include<stdio.h>
  
  int main()
  {
    int m = 10;
    int n, n1;
    n = ++m;
    n1 = m++;
    n--;
    --n1;
    n -= n1;
    printf("%d", n);
  
    return 0;
  }
  

• Relational Operators: In C, Every non-zero value is considered as 1(true) & Zero as 0(false).

• Logical Operators:

  • Expressions that use logical operators return 0 for false & 1 for true:

    Operator	Meaning
    &&	AND
    ||	OR
    !	NOT

  • The truth table for logical operators is shown below:

    A	B	A&&B	A || B	!A
    0	0	0	0	1
    0	1	0	1	1
    1	1	1	1	0
    1	0	0	1	0

• Comma Operator

  ```
  #include <stdio.h>
  int main(void)
  {
  int a, b, c, sum;
  sum = (a = 8, b = 7, c = 9, a + b + c);
  printf("Sum = %d\n", sum);
  return 0;
  }
  ```
  

• Ternary Operator

• sizeof operator: Unary Operator

Precedence & Associativity:

	Operator	Associativity	Precedence
()	Function Call	Left-to-Right	Highest 14
[]	Array Subscript	Left-to-Right	Highest 14
.	Dot (Member of Structure)	Left-to-Right	Highest 14
->	Arrow (Member of Structure)	Left-to-Right	Highest 14
!	Logical NOT	Right-to-Left	Highest 13
~	one's complement	Right-to-Left	Highest 13
-	Unary minus(Negation)	Right-to-Left	Highest 13
++	Increment	Right-to-Left	Highest 13
--	Decrement	Right-to-Left	Highest 13
&	Address-of	Right-to-Left	Highest 13
*	Indirection	Right-to-Left	Highest 13
(type)	cast	Right-to-Left	Highest 13
sizeof	sizeof	Right-to-Left	Highest 13
*	Multiplication	Left-to-Right	Highest 12
/	Division	Left-to-Right	Highest 12
%	Modulo (Remainder)	Left-to-Right	Highest 12
+	Addition	Left-to-Right	Highest 11
-	Subtraction	Left-to-Right	Highest 11
<<	Left-Shift	Left-to-Right	Highest 10
>>	Right-Shift	Left-to-Right	Highest 10
<	Less than	Left-to-Right	Highest 8
<=	Less than or equal	Left-to-Right	Highest 8
>	Greater than	Left-to-Right	Highest 8
>=	Greater than or equal	Left-to-Right	Highest 8
==	Equal to	Left-to-Right	Highest 8
!=	Not Equal	Left-to-Right	Highest 8
&	Bitwise AND	Left-to-Right	Highest 7
^	Bitwise XOR	Left-to-Right	Highest 6
|	Bitwise OR	Left-to-Right	Highest 5
&&	Logical AND	Left-to-Right	Highest 4
||	Logical OR	Left-to-Right	Highest 3
? :	Conditional	Right-to-Left	Highest 2
=, +=, *=, etc	Assignment Operator	Right-to-Left	Highest 1
,	Comma	Left-to-Right	Lowest 0

Type Casting:

• It is an Unary Operator.

• Order of Type Casting based on number of bytes required for a data-type is below:

  Automatic Type Conversion Order:
  
  Promotion/Demotion: long double, double, float, long int, int, char
  
  for e.g, long int l = 2L + 3 = 5L
  

• "Reliable & Readablity of Code": Strongly Recommended Explicitly Type Casting

  int x = 20, y = 3;
  float z = x/y; // z = 6.0 => Implicit/Automatic Conversion
  
  float z = (float)x/y; // z = 20.0/3 => 6.666666
  

Bitwise Operators:

• Operations on Bitwise Operators:

  • Bitwise AND
  • Bitwise OR
  • Bitwise XOR
  • Bitwise Left-shift (<<)
  • Bitwise Right-shift (>>)

• Truth Table:

  A	B	A&B	A | B	A^B
  0	0	0	0	0
  0	1	0	1	1
  1	0	0	1	1
  1	1	1	1	0

Control Statements:

• Control statements are used to change the order of execution.

• if-else/if-else-if/else-if-ladder: Choose between one & another and more.

  if(<condition>){
    ---;
    ---;
  }
  else if(<condition>){
    ---;
    ---;
  }
  else{
    ---;
    ---;
  }
  //We can have "if" without "else" also.
  

• while loop:

  while(<condition>){
    ---;
    ---;
  };
  

• do-while loop: Body will run atleast 1 time.

  do{
    ---;
    ---;
  }while(<condition>);
  

• for loop: To run a loop n number of times (n is known).

  for(initialization; condition; updation)
  {
    ---;
    ---;
  }
  

• Nested loop:

    if(){
      if(){
      }
      else{
      }
    }
  
    for(i = 1; i <= 5; i++) //Outer Loop
    {
      for(j = 1; j <= 3; j++) //Inner Loop
      {
      printf("%d %d", i, j);
      }
    }
  

• Infinite loop: Continuously run without termination.

  for(;;)
  {
    printf("Hi");
  }
  
  while(1)
  {
    printf("Hi");
  }
  
  int i = 1;
  while(i <= 5);
  {
    printf("Hi");
  }
  

  • Don't use != & == in float during while loop

break & continue:

• break & continue only breaks & continues out the inner loop it is the part of.

goto statement:

• Forward Jump/goto & Backward Jump/goto
• goto label;
• label: //identifier
• goto can jump only within a function
• try to avoid the use of goto in program
• In very deep nested loop , goto is really good application here.
• goto need 1 statement after label_identifier

Switch Case:

• Expression of switch is evaluated to only int/char/short/long
• case value must be integer/character constant
• switch expression does not allow for floating point number.