1. text segment - this contains the machine language
   instructions for your program, depending upon the header
   information this segment may be read only

2. data segment - this segment contains the global
   variables for your program, plus any memory that is
   allocated dynamically while your program is executing

3. stack segment - this segment contains the local
   variables for the procedures in your program, each time a
   procedure is called this segment could grow

• Both the data (heap) and stack segment can grow while the
  program is executing, the stack starts at the highest
  memory address and the data segment starts just after the
  text segment, they grow towards each other

Program Execution

• What happens when our program starts executing?

• Control is first transferred to the startup code that is
  provided by the C compiler and operating system - this
  code sets up the environment that the program runs in

• In the UNIX environment the startup code first points
  the stack pointer to the top of the memory space and then
  prepares to call the main() procedure in your program

• The main procedure should have the following
  declaration:

March 3, 1998

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