Basic Structure of C program

C basic structure Each instruction in C are written in a statement.
Each statement ends with ;
One C program consist of a group of statements
Program is executed in a sequence from top to bottom. Based on logic or requirement steps can be shifted in up or down direction. Small case letters are used and space is used between two commands.
We must declare a variable before using it.

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This is part of the program which is not executed by the compiler.
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We will start with writing a program to display a string Hello World
#include<stdio.h>
#include<string.h>

int main()
{
   char str[30] = "Hello World"; // Storing string data
   printf("%s",str); // Print the string
   return 0;
}
The output of above code is here
Hello Wold
We have first included to header files

#include<stdio.h>
#include<string.h>

First one is to include standard input output and other one for string functions. We will understand these header files later. Functions are written in C with two brackets , main() function is the function which C compiler first execute. We will also learn how to develop our own functions and use them in our program.

We declare a variable str and assigned 30 cells ( memory ) to it. We stored our string ‘hello world’ inside it and finally our function printf() display the output to screen.

Reading a string and then display

In above code we have assigned a string data to the variable , now we will ask user to input a string data and then we will display the same.
#include<stdio.h>
#include<string.h>

int main()
{
   char str[30];//
   printf("Enter your name ");
   scanf("%s", str);
   printf("Welcome %30s",str); // Print the string
   return 0;
}
scanf()

Sum of two integers

#include<stdio.h>
#include<string.h>

int main()
{
   int a,b,c;// Declaring three variables
   a=4;  // assigning data
   b=5;
   c= a + b;
   printf("Sum = %d", c); // Print the string
   return 0;
}
Output
Sum = 9

Sum and average of three numbers

#include<stdio.h>
#include<math.h>
int main()
{
   int a,b,c;// Declaring three variables
   float x,avg;
   a=3;  // assigning data
   b=5;
   c=6;
   x= (a + b + c);
   avg=x/3;
   printf("Sum of  three numbers  = %f", x); // Print the string
   printf("\n Average of three numbers  = %.2f", avg); // Print the string
   return 0;
}
Output is here
Sum of three number = 14.000000
Average of three numbers = 4.67
Data entered by user
#include<stdio.h>
#include<math.h>
int main()
{
   int a,b,c;// Declaring three variables
   float x,avg;
   printf("enter first number :");
   scanf("%d",&a);
   printf("enter second number :");
   scanf("%d",&b);
   printf("enter third number :");
   scanf("%d",&c);
   x= (a + b + c);
   avg=x/3;
   printf("Sum of  three numbers  = %f", x); // Print the string
   printf("\n Average of three numbers  = %.2f", avg); // Print the string
   return 0;
}
Output is here
enter first number : 4
enter second number : 5
enter third number : 6
Sum of three numbers = 15
Average of three numbers = 3
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