This document discusses basic C programming concepts including variables, data types, input/output, constants, keywords, program structure, comments, and compilation. It defines variables as names that store memory locations and data. It lists common C variable data types and their sizes in bytes. It describes constants as fixed values and keywords as reserved words. It provides examples of single line and multiple line comments. It demonstrates how to use printf and scanf for output and input. It also gives examples of basic C programs to calculate the area of a square and circle.

1. 1. Variable, Data types + Input/Output
Instruction & Operators
Condtional Statements
Loop Control Statement
Function & Recursion
Pointer
Array
Strings
Structures
File I/o
Dynamic Memory Allocation

2. CHAPTER -1
 Variables
 Keywords
 Constants
 Comments
 Structure
 Compilation

3. VARIABLE
VARIABLE IS THE NAME OF A MEMORY
LOCATION WHICH STORES SOME DATA.
 Variables Rules
 Variable are case sensitive
 1st character is alphabet or ‘_’
 No comma/blank space
 No other symbol other than’_’

4. VARIABLE DATA TYPES
 Data Type Size In Bytes
 Char or signed char 1
 Unsigned char 1
 Int or signed int 2
 Unsigned int 2
 Short int or Unsigned short int 2
 Signed short int 2
 Long int or signed long int 4
 Unsigned long int 4
 Float 4
 Double 8
 Long Double 10

5. CONSTANTS
 Value that don’t change (fixed)
Types
 Integer Constants 1,2,3,0,-1,-2
 Real Constants 1,0,2,0,3.14,2.4
 Character Constants ‘a’,’b’,’A’,’#’,’&’

6. KEYWORDS
 Reserved words that have special meaning to the
compiler
 32 Keyword in C
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

7. PROGRAM STRUCTURE#
#include <stdio.h>
Int main
{
Printf(“hello world”)
Return 0;
}

8. COMMENTS
 Lines that are not part of program
Single Line Multiple Line
// /*
*/

9. OUTPUT
 Printf(“hello world”);
 New Line
Printf(“hello world n”);
OUTPUT
CASES
1. Integers
Printf(“age is %d”,age);
2. Real Number
Printf(“value of pi is %f”,pi);
3. Characters
Printf(“star looks like this %c”, star);
Programm
#include<stdio.h>
Int main ()
{
Int age = 22;
Printf(“age is %d”, age);
Return 0;
}

10. INPUT
I/o Program
Scanf(“%d”,&age);
# include<stdio.h>
Int main()
{
Int a,b;
Printf(“enter a”);
scanf(“%d”,&a);
Printf(“enter b”);
Scanf(“%d”,&b);
//Int sum = a+b;
//Printf(“sum is : %d”, sum);
Printf(“sum is : %d”, a+b);
Return 0;
}

11. COMPILATION
 A computer program that transaction C code into machine code
Practice Qs 1
1- Write a program to calculate area of a square (side is given)
#include<stdio.h>
// area of square
Int main()
Int side ;
Printf(“enter side”);
Scanf(“%d”, &side);
Printf(“area is : %d”, side * side);
Return 0;
2- Write a program to calculate are of a circle. (side is given)
#include<stdio.h>
// area of square
Int main()
Float radius ;
Printf(“enter radius”);
Scanf(“%f”, &radius);
Printf(“area is : %f”, 3.14 * redius * redius);
Return 0;