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MASTERING C WITH MC KENZIE

Lesson Three

  C Programming Main Page
Review Lesson Two
Lesson Four (a)

Getting User Input

You Will Learn About :

• Using scanf( )
• The ampersand and scanf( )
• Integer Division

scanf( ) is used to obtain data from the user as input to a program.

Here is an example of how scanf( ) is used to get an integer value:

scanf("%d",&variable_name);"

The correct specifier must be used to match with the correct data type.

char %c, int %d, float and double %f, string %s

Another important point to note is that an ampersand is needed before the variable name. The ampersand means the "the memory address of "

  /* Program 3A - getting integer input  with scanf() */	
#include <stdio.h>

main()
{
       int   x, y, total; 	

       printf("Enter a number\n");      /* User prompt */
         scanf("%d",&x);         
           printf("Enter a second number\n");    
              scanf("%d",&y);                      
             total = x + y;			
       printf("The sum is   %d",total); 
  exit(0);
}

Instructions :

• Write source code as given
• Compile source code and correct syntax errors
• Save the program as prog3A
• Run and test the program with different values.

1. main( ) printf( ) scanf( ) and exit( ) are written in lower case characters.
2. Comments must be preceded by /* and ended with */
3. &     The ampersand is required before the variable name when using scanf( )
4. %d    Is needed when scanf( ) is working with integers
5. End all statements with a semi-colon

To use the printf( ) function to print an integer value requires the use of the specifier %d or %i which tells C exactly where within the print statement the value item must be placed.

Because intergers by definition cannot hold fractions, when we perform the division operation using integers the remainder is always lost. This is because a remainder represents a fraction.That is, if 5 is divided by 3 the computer will give 1 as the answer. It cannot represent the fraction using the two bytes of memory space allocated to integers. To get this program to generate accurate figures we should use the float datatype along with the %f specifier. This we will do in another program.

Test this program with the numbers given ( 5 and 3 ) and see for yourself.

  /* program 3B - Integer division */	
#include <stdio.h>

      main()
          {
            int   x, y, quo; 			

           printf("Enter an integer  dividend value \n");
           scanf("%d",&x);
          printf("Enter an integer divisor value \n");
       scanf("%d",&y);
    quo = x / y;		
  printf("The quotient is   %d .There is no remainder value ",quo);
exit(0);
}

Instructions :

• Compile source code and correct syntax errors
• Save the program as prog3B
• Run the program and test it with different values.
• Note your findings

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