Add chapter 4 to root, fix bit rot

Fixing the bitrot in chapter 4 after moving it meant looking at the OCR'd text
on archive.org, which is not good.  Here's how not good it was:

> A tiL.  (be it APPLESOFT, INTEGER, BINARY.  or TEXT type) con,i a t a of one
> or more sectors containing data.  Since the •• ctor i, the smallest unit of
> allocatable space on a di s kette, a file will use up at least one sector even
> if it i a Ie •• than 256 bytes long; the remainder of the sector is w • • ted.
> ThuB , a file containing 400 characters (or bytes) of data will occupy one
> entire sector and 144 bytes of another with 112 bytes wasted .  Knowing these
> facts, one would expect to be able to use up to 16 times 35 times 256 or
> 143,360 bytes of space on a diskette for files.  Actually, the largest file
> that can be stored is about 126,000 bytes long.  The reason for this is that
> some of the sectors on the di a kette .uat be used for what is called
> ·ove[head- .
>
> <Figure 4.1>
>
> Overhead sectors contain the iMage of DOS which is 10ad •• 1 when booting the
> diskette, a list of the nallles and loes,lollll of the files on the diskette,
> and an accounting of the sectors which are free for use with new files or
> expon.lu".  of existing files.  An example of the way DOS uses lectDr.  ,.
> given in Pigure 4 .  1 .

Yeah....  You see why I was so excited by the source text?  :)
This commit is contained in:
T. Joseph Carter 2017-07-20 18:52:59 -07:00
parent fe4c578ff9
commit 4461e45278

View File

@ -13,34 +13,24 @@ The way DOS allocates these tracks of
sectors is the subject of
this chapter.
A file (be it APPLESOFT,
INTEGER, BINARY, or TEXT type)
consists of one or more sectors
containing data. Since the sector is
the smallest unit of allocatable
space on a diskette, a file will use
up at least one sector even if it is
less than 256 bytes long; the
remainder of the sector is wasted.
Thus, a file containing 400
characters (or bytes) of data will
occupy one entire sector and 144
bytes of another with 112 bytes
wasted. Knowing these facts, one
would expect to be able to use up to
16 times 35 times 256 or
143,360 bytes of space on a diskette
for files. Actually, the largest file
that can be stored is about 126,000
bytes long. The reason for this is
that some o\x86PL@\x85TCESHWV\x87HK\x86PL@)ALUOCQP@\x85HQUS\x84DB\x85PUCA\x84@JW\x86PODQ\x84LU*FGIH@@\x87\x85HQAUOCGA\x85\x8b\x86\x84hSAVNCGB\x86UCDSHWV+EKKRDMI\x86PL@\x85LIEAC\x85HC\x86`hw\x87POLEO\x84LU+IHGA@A\x84PO@I*EJKSNJC\x86QMA\x87@OVNBSPC\x8a\x87E\x86KLVQ\x85JC\x85QM@)IFIAU\x87DIB\x84HHGGQLIKV\x87HC\x86PL@\x85@NI@U\x87HK*QL@\x85@LUOCQP@\x89\x84DIB\x87EI\x86EEDJPKPNIB\x87HC)RMB\x85VCGPKVW\x26 which are free for use
with new files or expansions of
existing files. An example of the way
DOS uses sectors is given in Figure
4.1.
A file (be it APPLESOFT, INTEGER, BINARY, or TEXT type) consists of one or more
sectors containing data. Since the sector is the smallest unit of allocatable
space on a diskette, a file will use up at least one sector even if it is less
than 256 bytes long; the remainder of the sector is wasted. Thus, a file
containing 400 characters (or bytes) of data will occupy one entire sector and
144 bytes of another with 112 bytes wasted. Knowing these facts, one would
expect to be able to use up to 16 times 35 times 256 or 143,360 bytes of space
on a diskette for files. Actually, the largest file that can be stored is about
126,000 bytes long. The reason for this is that some of the sectors on the
diskette must be used for what is called "overhead".
.sp1
*** INSERT FIGURE 4.1 ***
.sp1
Overhead sectors contain the image of DOS which is 1oaded when booting the
diskette, a list of the names and locations of the files on the diskette, and an
accounting of the sectors which are free for use with new files or expansions of
existing files. An example of the way DOS uses sectors is given in Figure 4.1.
DISKETTE SPACE ALLOCATION
The map in Figure 4.1 shows that the