CS1001 Lecture 19

1
CS1001 Lecture 19

• Some More Arrays Processing
• Application of Arrays
• Stacks
• handouts StackTest and QueueTest

2
STOP Statement

• END PROGRAM program_name
• last statement of every program
• indicates to the compiler the end of the program
• halts the execution of the program
• STOP or STOP constant
• terminates executive of the program
• in the second form
• constant is an integer constant or a character
  string
• constant is printed out at termination by that
  STOP

3
Compile-time and Run-time arrays

• Compile-Time arrays
• type, DIMENSION (lu) list _of_array_names
• l is the lower limit of the array, u is the upper
  limit of the array
• allocate fixed number of spaces for array at
  compiling time
• Two problems
• waste of space when too much is allocated
• possibility of array overflow is not enough is
  allocated
• Allocatable or run-time array
• memory is allocated during run-time
• Declare arrays to be allocatable,
• allocate the required space,
• and if needed, deallocate the space.

4
Run-time array

• Declaration
• type, DIMENSION ( ), ALLOCATABLE list
• or
• type, DIMENSION ( ) List
• ALLOCATABLE list
• E.g., REAL, DIMENSION ( ), Allocatable A,B
• Allocate Space
• ALLOCATE (list)
• or
• ALLOCATE(list, STATstatus_variable)
• E.g. PRINT , enter size of arrays A
  and B
• READ , N
• ALLLOCATE( A(N), B(0N1), STAT status)
• IF (status .NE. 0) STOP Not enough memory
  

Status_variable set to 0 if operation is
successful
5
Run-time array

• Deallocate Space
• DEALLOCATE (list)
• or
• DEALLOCATE(list, STATstatus_variable)
• status_variable will be set to zero if
  operation is successful

6
Arrays as arguments

• Intrinsic functions (page 548 and Appendix D)
• MAXVAL(A) returns the maximum value of array A
• MINVAL(A) returns the minimum value of array A
• SIZE(A) returns the number of elements in array
  A
• SUM(A) returns the sum of the elements of array A
• User-Defined subprogram
• actual array argument must be declared in calling
  program unit
• corresponding formal array argument must be
  declared in the called subprogram unit

INTEGER, DIMENSION( ) ALLOCATABLE Stack .
. . Call PUSH (Stack) . . . SUBROUTINE
Push(Stack) INTEGER, DIMENSION ( ),
INTENT(INOUT) Stack
Calling unit
Callee unit
7
Stack

• A data structure used to implement
  Last-in-first-out (LIFO) processes
• e.g. stack of trays in the cafeteria

• Two operations
• Push
• Pop
• Some design issues
• How long (or deep) should the stack be (i.e.,
  the dimension of the stack)?
• When push, is there room in array?
• When pop, is the stack empty ?

Top
Stack(top)

Stack(4)
Stack(3)
Stack(2)
Stack(1)
Stack