>'BOOK1N - WORKING WITH FILES
     tHERE ARE SEVERAL TYPES OF MEDIA THAT THE trs80 MAY BE INSTRUCTED TO LOAD/SAVE DATA FROM/TO.  pROBABLY THE MOST PREVALENT IS TAPE STORAGE, BUT FLOPPY/RIGID DISK SYSTEMS ARE BECOMING MORE POPULAR AS THE PRICE OF THESE DEVICES IS DROPPING DRASTICALLY.  rEGARDLESS OF THE TYPE OF MEDIA USED, ALL DATA IS STORED IN A VERY STRUCTURED FORMAT CALLED A file.  a FILE MAY RANGE IN CONTENTS ANYWHERE FROM A PROGRAM TO A PURE BIT STREAM OR DATA FILE.  a FILE IS SIMPLY A SERIES OF BYTES THAT ARE PLACED IN A LOGICAL MANNER ON THE MEDIA SO THAT IT MAY BE RE-LOADED INTO THE COMPUTER.  oN MOST STORAGE SYSTEMS (TAPE AND DISK), THE DATA IS PLACED ONTO THE MEDIA IN A SEQUENTIAL FASHION.  tHE OPERATING SYSTEM MAY PLACE ADDITIONAL INFORMATION INTO THE FILE TO FACILITATE EASY LOCATION/LOADING.  tHIS EXTRA INFORMATION CAN RANGE FROM SIMPLY THE NAME OF THE FILE, TO COMPLEX LOADING MARKERS THAT ARE INTERSPERSED THROUGHOUT THE FILE TO DIRECT THE DATA TO PARTICULAR MEMORY AREAS OF THE COMPUTER WHEN RE-LOADED.
     nOW THAT WE KNOW THAT A FILE IS SIMPLY A COLLECTION OF DATA PLACED ONTO A FORM OF MEDIA IN A MANNER THAT IT MAY BE RE-LOADED BACK INTO THE COMPUTER, LET'S EXAMINE JUST WHAT WE MAY NOW DO WITH THE STORED INFORMATION.  lET'S START OFF BY ASSUMING THAT WE ARE WORKING ON A TAPE SYSTEM, WHICH IS PROBABLY THE MOST PRIMITIVE YET SIMPLE FORM OF MASS STORAGE.  sUPPOSE THAT WE HAVE JUST WRITTEN A PROGRAM AND TYPED IT INTO THE COMPUTER MEMORY.  wE NOW DECIDE THAT WE ARE FINISHED WITH THE CURRENT PROGRAM AND WANT TO BEGIN ANOTHER ONE, BUT DO NOT WANT TO DESTROY THE INFORMATION THAT WE HAVE JUST ENTERED.  fIRST WE ISSUE A COMMAND TO OUR OPERATING SYSTEM TO 'SAVE' OUR PROGRAM TO THE TAPE DECK.  wE MAY TYPE IN A COMMAND SUCH AS csave"NAME".  tHE OPERATING SYSTEM WILL THEN BEGIN A COMPLEX SERIES OF INSTRUCTIONS TO WRITE OUR PROGRAM TO THE TAPE DECK.  tHE ABOVE PROCESS WILL WRITE OUR PROGRAM TO A file ON THE TAPE MEDIA IN A FORM THAT WILL ALLOW US TO RE-LOAD THE DATA BACK INTO THE COMPUTER.  iN A SIMILAR FASHION, SUPPOSE THAT THE PROGRAM WE HAD JUST WRITTEN ALSO HAD TO ACCESS A BLOCK OF data, OR NUMBERS THAT ARE REQUIRED TO PERFORM THE OPERATIONS THAT WE NEED.  sAY THAT OUR PROGRAM WAS WRITTEN TO HELP US DECIDE WHICH STOCK TO BUY TODAY, BUT IN ORDER TO MAKE THE BEST DECISION, WE NEEDED TO TAKE YESTERDAYS FIGURES AND RUN THEM THROUGH A FORMULA TO MAKE THE CORRECT ESTIMATION.  tHE DATA THAT WE NEED MAY BE IN THE PROGRAM IN ANY OF SEVERAL FORMS, OR IT MAY BE STORED ON MAGNETIC MEDIA IN THE FORM OF A file.  oUR PROGRAM (WHICH IS ALSO A FILE) MAY READ IN THE data file FROM THE TAPE FOR RAPID ACCESS TO THE INFORMATION.  iN A SIMILAR FASHION, THE INFORMATION MAY HAVE BEEN PLACED ON A FLOPPY DISKETTE IN THE FORM OF A SERIES OF files.  sO SIMPLY SPEAKING, A file IS MERELY A COLLECTION OF DATA THAT IS PLACED ONTO SOME FORM OF MASS STORAGE DEVICE.
     a FILE MAY BE FURTHER BROKEN DOWN INTO A SERIES OF records, WHICH ARE SIMPLY ARBITRARY UNITS THAT ARE DEFINED AT THE TIME THE FILE IS CREATED.  a RECORD MAY RANGE IN LENGTH FROM A SINGLE BYTE TO THE ENTIRE LENGTH OF THE FILE.  rECORDS ARE THEN DEFINED MERELY AS A COLLECTION OF BYTES, AND A FILE IS SIMPLY A COLLECTION OF RECORDS.  tHUS WE HAVE DEFINED THE THREE MAJOR ELEMENTS OF OUR SET OF DATA:  THE byte, THE record, AND THE file ITSELF.
     oN A TAPE STORAGE SYSTEM, WE MUST READ THE DATA BACK INTO THE COMPUTER IN A serial FASHION, WHICH IS TO SAY THAT WE MUST BEGIN READING THE DATA BYTES STARTING FROM THE BEGINNING AND WORKING ALONG THE LENGTH OF THE TAPE.  iF THE TAPE IS POSITIONED BEYOND THE POINT WHERE OUR DATA BEGINS, WE MUST MANUALLY PRESS BUTTONS ON OUR TAPE DECK TO MOVE THE DESIRED PORTION OF TAPE TO A 'REWOUND' POSITION.  tHERE ARE NO COMMANDS THAT WE MAY ISSUE TO THE COMPUTER TO TELL IT TO REWIND THE TAPE BACK TO THE BEGINNING.  oN A DISK SYSTEM, HOWEVER, THE DATA MAY BE READ IN ADDITIONAL WAYS.  dUE TO THE UNIQUE STRUCTURE OF THE FLOPPY DISKETTE, IF WE 'MISS' THE DESIRED PORTION OF OUR STORED FILE, WE WILL HAVE ANOTHER CHANCE AS SOON AS THE DISK MAKES ONE MORE TURN IN THE DISK DRIVE.  tHERE IS NO 'REWIND' AVAILABLE ON A DISKETTE, SINCE IT IS SIMPLY A CIRCLE IN ITSELF.
