10.1. Your executable   

Consider the following pseudocode: 


      algorithm Fish ( ...  )

      var y: integer

      begin

             y  y*25

      end.

If this is converted into some computer language such as Pascal, Java or C, then after a compile command on this program, the computer has the machine instructions in memory ready to start. These instructions may look typically like this: 

    MOVE   0,y(17)              ;   Position of x on stack

    IMULT  0,25                 ;   x*25

    MOVEM  0,y(17)              ;   Stores to Stack

    JRST   Operating_system     ;   RETURN to Operating System.

The program in finally converted to Machine language instructions after being compiled and linked by a linking loader program. 

   /////// DATA     Low address

                    Once it is as in Fig 1, main can call

                    procedure 1, 2 etc. by using address of

   PROCEDURE 1      procedure 1, 2 etc. in a CALL instruction.

                    ALL addresses are known.

   FUNCT 1


                    This is same situation as in PL0 when

   PROCEDURE 2      program has been compiled and procedure

                    INTERPRET is ready to execute.


   MAIN

                     High address


              N.B.:  PL0 programs are interpreted by the Java

   HEAP              program Pl0.java; whereas normal programs

                    are run through a compiler such as Pascal,

                    FORTRAN, COBOL which produce (finally)

                    machine language instructions.

   Stack             A Java program is interpreted just like Pl0!


      Figure 1