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DOS Level 1:
SOFTWARE: Sets of programs (stored sets of instructions) that govern
the operation of computer system and make the hardware run. These
programs (instructions) tell the hardware how to perform a particular
task such as word processing, games, database management, etc.
DOS
---
DOS - Disk Operating System - is a piece of software. However, it is
different from most software because a computer cannot run without it. It is
the first piece of software that is installed in RAM every time the computer
is turned on.
When the user first starts the computer, the DOS files must be available in
either the A drive or on a Hard Disk. The computer finds the desired DOS
files and automatically loads them into RAM. This process is often called
"BOOTING" the computer -from the computer pulling itself up by its BOOTstraps.
TO LOAD DOS
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"Cold" Boot: Turning the computer on
"Warm" Boot: The computer has already been started, but you wish to
completely "clean-out" RAM and re-load DOS. This is a
much faster method of re-starting the computer since it
skips the usual system checks. To accomplish, you press
three keys simultaneously: <CTRL>-<ALT>-<DEL>
DOS performs 2 functions:
1. Links the Hardware
2. Allows for file management
We think of most software as enabling us to create something - like a document
or a spreadsheet. DOS's mission is vital. Firstly, it enables the hardware
devices to properly communicate with each other. It is a set of instructions
so that the computer's brain understands how its arms and legs operate
(keyboard, monitor, printers,...). We take this ability for granted. It is
like starting a car - many complex systems must work in unison for it to work,
yet we take it for granted that it will start.
The second function of DOS is also important. We must have a means to manage
the files that we save on our Floppy Disks or Hard Drives. There are times
when we wish to copy these files from one disk to another, or erase them, or
determine which files are on a disk. These tasks are performed often and the
software required to do so is DOS.
When DOS has been properly loaded from either a Floppy Disk or a Hard Drive,
the familiar "DOS Prompt" will appear. This prompt will look something
like this:
A>
This symbol signals 3 things:
1. DOS has been properly loaded into RAM
2. "A" is the DEFAULT drive
3. Awaits a DOS file management command
Each disk drive and hard disk has a letter associated with it. If a drive is
considered the DEFAULT drive, then the computer will always assume that the
information needed is in that drive, OR if something you have created is saved
- it will be saved to that drive, UNLESS you tell the computer otherwise.
All types of disks contain files. We use DOS as a software tool to manage
these files. We not only tell the computer which file we want to erase or
copy but also which drive it is currently in.
DOS FILE CONVENTIONS
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FILES: Any related set of instructions - programs, documents,
spreadsheets, etc.. A floppy disk is like a file cabinet with each
folder representing files on the disk (in the cabinet).
Rules: filename | extension (optional)
|
1-8 Characters | 1-3 Characters
No Spaces | No Spaces
Letters/Numbers| Letters/Numbers
If an optional extension is used, a period is used to separate the filename
and extension.
Many characters are allowed in filenaming. The following are INVALID
for filenames OR extensions:
. " / \ [ ] : | < > + = ; ,
Each file has a name. When you want DOS to act on a file, you must
specify its proper name (including its extension if applicable). A
file's name is made up of a filename and an optional extension:
saledata.jly
? ? ???Extension (optional) - UP TO 3 CHARACTERS
? ??Period required as Separator IF extension used
???Filename - UP TO 8 CHARACTERS
Some filenames: SAMPLE
SAMPLE.DOC
BUDGET.WK1
Two files with the same exact name CANNOT exist on the same disk or
subdirectory (subdirectories are covered under hard disk sections).
FILESIZE
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Computers use 1 BYTE to represent 1 character such as a letter of the
alphabet, a number, a punctuation mark, a space, etc. A BYTE is also a unit
of measure since it represents 1 character. We measure the size of RAM in
Bytes, as well as the size of Files/Programs in Bytes.
We also measure the capacity of Disks and RAM in Bytes. So many Bytes
can be contained on disks or RAM that we talk about:
KILObytes = 1,000 bytes (often abbreviated "k")
MEGAbytes = 1,000,000 bytes (often abbreviated "meg")
5.25" disks Double Sided, Double Density = 360k
Double Sided, High Density = 1.2meg
3.5" disks Double Sided, Double Density = 720k
Double Sided, High Density = 1.4meg
Hard Drives = 10meg, 20meg, 30meg, 40meb, 60meg,......350meg
FREQUENTLY USED DOS COMMANDS
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When DOS is booted, a copy of INTERNAL DOS commands are placed in the
computer's memory (RAM). These are called INTERNAL commands because
they stay in RAM until the computer is turned off. To use these
commands you do not have to re-insert the DOS diskette.
The rest of the commands on the DOS disk are called EXTERNAL commands
because they are NOT read into RAM when you boot DOS. Rather, to use them
DOS must accessible in one of the disk drives.
The following are some frequently used DOS commands:
INTERNAL ? EXTERNAL (Insert DOS in Drive A)
?
DIR TYPE ? FORMAT CHKDSK
COPY CLS ? DISKCOPY
ERASE DATE ? COMP
RENAME TIME ? DISKCOMP