PROB2_MAIN
   Demonstrate how a FORTRAN program can call a C subroutine.
  
   Set the value of two integers I1 and I2.
   Call a C routine to compute I1 + I2.
  
   I1 =           42
   I2 =           22
   Subroutine INT_ADD_SUB returns output I3 =           64
   Function INT_ADD_FUNC returns output  I4 =           64
  
   Set the value of two reals R1 and R2.
   Call a C routine to compute R1 + R2.
  
   R1 =    42.00000    
   R2 =    22.00000    
   Subroutine REAL_ADD_SUB returns output R3 =    64.00000    
   Function REAL_ADD_FUNC returns output  R4 =    64.00000    
  
   Set the value of two double precision values D1 and D2.
   call a C routine to compute D1 + D2.
  
   D1 =    42.0000000000000     
   D2 =    22.0000000000000     
   Subroutine DOUBLE_ADD_SUB returns output D3 =    64.0000000000000     
   Function DOUBLE_ADD_FUNC returns output  D4 =    64.0000000000000     
  
 PROB2_MAIN:
   Normal end of execution.

C routine INT_ADD_SUB_ receives input I1 = 42.
C routine INT_ADD_SUB_ receives input I2 = 22.
C routine INT_ADD_SUB_ sends back output I3 = 64.

C routine REAL_ADD_SUB_ receives input R1 = 42.000000.
C routine REAL_ADD_SUB_ receives input R2 = 22.000000.
C routine REAL_ADD_SUB_ sends back output R3 = 64.000000.

C routine DOUBLE_ADD_SUB_ receives input R1 = 42.000000.
C routine DOUBLE_ADD_SUB_ receives input R2 = 22.000000.
C routine DOUBLE_ADD_SUB_ sends back output R3 = 64.000000.