Receiving Input of C Program
Receiving Input
In the program discussed below we
assumed the values of p, n and r to be 1000, 3 and 8.5.
Every time we run the program we would get the same value for simple interest.
If we want to calculate
simple interest for some other
set of values then we are required to make the relevant change in the program,
and again compile and execute it. Thus the program is not general enough to
calculate simple interest for any set of values without being required to make
a change in the program. Moreover, if you distribute the EXE file of this
program to somebody he would not even be able to make changes in the program.
Hence it is a good practice to create a program that is general enough to work
for any set of values.
To make the program general the
program itself should ask the user to supply the values of p, n and
r through the keyboard during execution. This can be achieved using a
function called scanf( ). This function is a counter-part of the printf(
) function. printf( ) outputs the values to the screen whereas scanf(
) receives them from the keyboard. This is illustrated in the program shown
below.
/* Calculation of simple interest */
/* Author gekay Date 25/05/2004 */
main( )
{
int p, n ;
float r, si ;
printf ( "Enter values of p, n, r" ) ;
scanf ( "%d %d %f", &p, &n, &r ) ;
si = p * n * r / 100 ;
printf ( "%f" , si ) ;
}
The first printf( ) outputs
the message ‘Enter values of p, n, r’ on the screen. Here we have not used any
expression in printf( ) which means that using expressions in printf(
) is optional.
Note that the ampersand (&)
before the variables in the scanf( ) function is a must. & is
an ‘Address of’ operator. It gives the location number used by the variable in
memory. When we say &a, we are telling scanf( ) at which
memory location should it store the value supplied by the user from the
keyboard. The detailed working of the & operator would be taken up
in Chapter 5.
Note that a blank, a tab or a new
line must separate the values supplied to scanf( ). Note that a blank is
creating using a spacebar, tab using the Tab key and new line using the Enter
key. This is shown below:
Ex.: The three values separated
by blank
1000 5 15.5
Ex.: The three values separated
by tab.
1000 5 15.5
Ex.: The three values separated
by newline.
1000
5
15.5
So much for the tips. How about
another program to give you a feel of things...
/* Just for fun. Author: Bozo */
main( )
{
int num ;
printf ( "Enter a number" ) ;
scanf ( "%d", &num ) ;
printf ( "Now I am letting you on a secret..." ) ;
printf ( "You have just entered the number %d", num ) ;
}
