W To date we have discussed elementary high level language programming and low level assembler programming, one of the benefits of C is the integration of both , this requires a revisit to 'C' to discover advanced features.

Number ranges and logical expression within C

  Within C we have seen and used various type functions i.e. int, char, Boolean, float. These types are limited in storage size, consider the following example.

Example
  
  Write a program to input two integer numbers and display the addition.
 
Answer
 
  #include stdio.h
  void main()
  {
  /*Author : Mr James Mc Carren 
  Company: Staffordshire University 
   Date: 26th August 2012 
  Version 1.0 
  Function : To add two integers numbers together       
   Modifications:   none*/
  char prompt;
  short int a,b;
  printf("Please enter in number 1  : ");
  scanf("%d",&a);
  printf("\n\rPlease enter in number 2 :");
  scanf("%d",&b);
  printf("\n\r The total of %d + %d is %d",a,b,a+b);
  printf("Press any key to exit \n\r");
  scanf("\n%c",&prompt);
  }   
 
  If we enter in the following numbers 
 
  Number 1 40000
  Number 2 50000
 
The program produces
 
  Please enter in number 1  : 40000
 
  Please enter in number 2 :  50000
 
   The total of -25536 +-15536 is 24464

 There appears to be a limit on the maximum number stored in a integer variable.  This is true for all the variables used so far i.e
 
  Char    127 to -128
  int    32767 to -32768
  float     3.40282347e+38 to 1.17549435e-38
 
To extend these ranges we can use extended types i.e
 
  long int    2147483647 to -2147483648
  double   1.7976931348623157e+308 to 2.2250738585072014e-308
 
To extend the ranges even further we can use the unsigned type, this removes the sign space. This is commonly used in microprocessor development systems are hex/binary is rarely signed i.e.

     unsigned char 
    unsigned int
    unsigned  float
    unsigned double
    unsigned long int

This is why when we cast data; it may not always work i.e trying to fit a float into a int,  Because a float is physically bigger than an int . Coupled with this is a extended range of format commands i.e. %lx %ld ' long hex long decimal' %ux %ud ' unsigned long hex unsigned long int.