User Input

Let us see how to accept values from a user and display the output

main()

{

     

      int phone;

      printf("Pl Enter Your Phone Number ..... ");

      scanf("%d" , &phone);

      printf("Your Phone Number Is .... %d",phone);

      getch();

     

      }

This program ask user for phone number , stores the value in a variable called phone and display the output

Now let us examine the new element in the program

scanf("%d" , &phone);  - scanf is another function like ptintf , just like printf is used to display something on the screen scanf is used to get input from the keyboard and store it in a variable . 

 Let us see some more programs which take other data types

For floats we have

main()

{

     

      float salary;

      printf("Pl Enter Your salary ..... ");

      scanf("%f" , &salary);

      printf("Your salary Is .... %f",salary);

      getch();

     

      }

For doubles we have

 main()

{

     

      double pi;

      printf("Pl Enter value of pi ..... ");

      scanf("%lf" , &pi);

      printf("value of pi is .... %lf",pi);

      getch();

     

      }

For character  we have

main()

{

     

      char c;

      printf("You are male or female(M/F) ..... ");

      scanf("%c" , &c);

      printf("You are .... %c",c);

      getch();

     

      }

So we see how we can accept different data types from user and display them , sometimes if we use many scanf in the same program the value stored in previous scanf causes problem , so in order to solve this we use a function called fflush(stdin) , this function just clears the memory from previous data , but in order to use flush(stdin) function ,  we have to ask the compiler to include the file containing this function and we do this by writing  #include<stdio.h> at very top of the program . 

This might confuse you at this moment but as we go further everything would be clear

Now let us write a little bit of complex program using all what we learned

#include<stdio.h>

main()

{

      int mobile_number;

      int age;

      int land_line;

      char gender;

      float salary;

      double tax;

     

      printf(">>>>>>>>>>>Welcome<<<<<<<<<<<<< \n");

      printf("Enter Mobile Number............ ");

      scanf("%d",&mobile_number);

      fflush(stdin);

      printf("Enter age...................... ");

      scanf("%d",&age);

      fflush(stdin);

      printf("Enter Land Line Number......... ");

      scanf("%d",&land_line);

      fflush(stdin);

      printf("Enter Gender (M/F)............. ");

      scanf("%c",&gender);

      fflush(stdin);

      printf("Enter Salary................... ");

      scanf("%f",&salary);

      fflush(stdin);

      printf("Enter All Time Tax............. ");

      scanf("%lf",&tax);

      fflush(stdin);

      printf("===========================================\n");

      printf("Your Mobile Number Is %d\n",mobile_number);

      printf("Your Age Is %d\n",age);

      printf("Your Land Line Number Is %d\n",land_line);

      printf("===========================================\n");

      printf("Your Gender Is %c\n",gender);

      printf("Your Salary Is %f\n",salary);

      printf("Your Total Tax Is %lf\n",tax);

      printf("===========================================\n");

           

      getch();

     

      }  

  

It may look big but it is very simple actually , it just ask the user for some information , stores the information in  variables and display the output

      

Before going further let me say something about commenting a program , well comments are used by the programmer to explain some piece of code 

comments are not  part of the program , 

comments just make the program user friendly and readable , 

we can write comments beginning with two slashes like 

//comments goes here 

for multiple lines 

/* multi line comments */ 

One example will be

/*

Program to accept a phone number and display it (this is a comment)

*/

main()

{

     

      int phone;      // we declare a variable

      printf("Pl Enter Your Phone Number ..... ");

      scanf("%d" , &phone);     //accept value

      printf("Your Phone Number Is .... %d",phone);    //display the output

      getch();

     

 }