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2007-03-01
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┴ ╬┼╫ ╨┴├╦┴╟┼ ╞╥╧═ ╚╧╠╠┴╬─
BY ─ICK ╦LINGENS,
─UTCH ├╧═┴╠ ╒SERS ╟ROUP
╫HEN WE CREATED A LARGE PROGRAM WITH
A LOT STRINGS IN WHICH WE STORED A
HELP MENU (IT WAS A DISK MONITOR), WE
WERE NOT ABLE TO EXTEND THAT PROGRAM
WITH MORE DISK OPERATIONS, BECAUSE
ALL MEMORY WAS OCCUPIED.
╘WO POSSIBILITIES WERE LEFT:
- LEAVING OUT THE HELP MENU
- STORING THE HELP STRINGS IN ANOTHER
PART OF THE MEMORY.
╫E DID THE LATTER: WE CREATED A ╥┴═
DISK (A TEXT BUFFER) AS A PACKAGE AND
WE CALLED THAT PACKAGE ╘┼╪╘.
╘HE NEW PACKAGE HAS 4 PROCEDURES AND
ONE FUNCTION:
╨╥╧├ GETIN(╥┼╞ X$)
╨╥╧├ PUT(╥┼╞ X$)
╨╥╧├ RESET
╨╥╧├ REWRITE
╞╒╬├ EOT
╘HE PROCEDURE ╟┼╘╔╬ FETCHES A STRING
FROM THE BUFFER. ─URING THIS FETCH
THERE IS A TEST ON READING THE END OF
THE BUFFER. ╔F SO, AN ERROR MESSAGE
IS PRINTED AND THE PROGRAM IS
STOPPED.
╘HE PROCEDURE ╨╒╘ DOES THE REVERSE.
╔T PUTS A STRING INTO THE BUFFER.
╔F THE BUFFER IS FULL, THE MESSAGE
'OUT OF MEMORY' IS PRINTED.
╔N THE BUFFER THERE IS ROOM FOR
NEARLY 16K┬.
╘HE PROCEDURE ╥┼╙┼╘ DIRECTS THE
READING POINTER TO THE FIRST POSITION
IN THE BUFFER. ╘HIS STATEMENT CAN BE
USED TO READ AGAIN FROM THE
BEGINNING.
╘HE PROCEDURE ╥┼╫╥╔╘┼ DIRECTS THE
READING AND WRITING POINTER TO THE
FIRST BUFFER POSITION. ╔T EMPTIES THE
BUFFER!
╘HE FUNCTION ┼╧╘ HAS THE VALUE ╘╥╒┼
IF THE READING POINTER IS IN THE SAME
POSITION AS THE WRITING POINTER. ╔F
┼╧╘=╘╥╒┼, THAN THERE IS NO MORE TEXT
IN THE BUFFER.
├OMPARE THIS FUNCTION WITH THE ├╧═┴╠
FUNCTION ┼╧╞(FILE NUMBER).
┴N EXAMPLE.
╒╙┼ TEXT
REWRITE // EMPTIES BUFFER
─╔═ X$ ╧╞ 10
╞╧╥ T:=0 ╘╧ 9 ─╧
X$:+╙╘╥$(T)
┼╬─╞╧╥ T
PUT(X$)
RESET // READ POINTER IN FIRST
POSITION
╥┼╨┼┴╘
GETIN(X$)
╨╥╔╬╘ X$
╒╬╘╔╠ EOT
┼╬─ "╘HAT'S IT!"