/* ------------------------------------------------------------------------   
// Figure 4.25:  Ramp up and down.
//     Output a series of voltage values that ramp up from 0 to some    
//     maximum and then back down to 0 again in one-volt increments.                  
// ------------------------------------------------------------------------  
*/
#include <stdio.h>             
#define  LOWER  5 
#define  UPPER  10

void main( void )                                              
{
    int vmax;       /* Voltage maximum of ramp */
    int volts;      /* Current voltage value */      

    printf( "\n Enter the maximum voltage for the ramp: " );  
    scanf( "%i", &vmax );                                   
    
    while (vmax < LOWER || vmax > UPPER) {  /* Check for valid input. */
        printf( "\n Input=%i is not between %i and %i."        
                "\n Try again.  Please enter a voltage: ", 
                vmax, LOWER, UPPER );    
        scanf( "%i", &vmax );                                         
    }
    
    puts( "\n" );                             
    volts = 0;                  /* We will start and end at zero volts. */ 
    while (volts < vmax) {      /* Ramp up */                   
        printf( " Voltage = %i\n", volts );              
        volts++;                                             
    }
    puts( "\n" );               /* Voltage is now at maximum. */
    
    while (volts > 0) {      /* Ramp down */           
        printf( " Voltage = %i\n", volts );         
        --volts;                        
    }                           /* Voltage is back down to 0. */
}