try yourself |run program

#include <stdio.h> 
#include <conio.h> 
void main(){ 
 float a;
 clrscr();
 printf("Enter of a: ");
 scanf("%f",&a);/*  & is used before variable name when you want to read data*/
 printf("\n value of a = %f",a);
 getch();
}

Program Output

Enter of a: 121.12 
value of a = 121.120003