As I prepare for CompTIA's A+ Certification I will post my revision notes here.

Friday, January 27, 2006

Files, Directories Switches and Filters in DOS

To view the contents of a disc or drive in DOS you need to use the DIR command at the command prompt.
To see the contents of C: make sure you have navigated to the C> prompt, using the CD command. Then type DIR and return. You should see the contents of the C drive. If the contents go over more than one page the use the DIR /P command to page the results.
To view the contents of subdirectories of C use the following syntax for the Dos directory:

C> DIR \DOS /P

To sort all the files alphabetically you can use the SORT filter.

C> DIR \DOS |SORT

Wildcards are useful for only selecting files containing certain characters or of certain file extensions. The example below selects only .COM files:

C> DIR \DOS\*.COM

The * wildcard represents any number of characters while the ? Wildcard represents only one character.
Since MS-DOS version 7 you can use more than one * wildcard in a command.

All pre 7 DOS versions used the 8.3 filename convention. That's versions prior to Windows 95. All filenames had a maximum length of 8 alphanumeric characters and a 3 letter extension. From Windows 95 onwards however filenames could be up to 255 characters, but for backwards compatibility Windows would automatically create an alternate 8.3 format filename reference for each file.

Versions of MS-DOS

I've included this table of MS-DOS versions to assist in understanding how MS-DOS evolved. The history of DOS is not tested on the A+ exam, but as I've found out it does help and is a useful reference.

VersionDateMain Changes
1.0198186-QDOS written by Seattle Computer Products is renamed to MS-DOS by Microsoft. IBM refers to it as PC-DOS.
1.251982Supports double-sided discs (PC-DOS 1.1)
2.01983Supports 10MB hard discs and 360KB floppy discs
2.111983Supports extended character sets
3.01984Supports 32MB hard discs 1.2MB floppy discs
3.11984Supports networking
3.21986Supports 31/2", 720KB floppy discs
3.31987Supports PS/2 computers, partitioning, 31/2, 1.44MB floppy discs
4.01988Supports extended memory, graphical user interface DOS shell and disc partitions above 32MB
5.01991DOS can now run in high memory, supports 2.88 floppy discs and full screen editor
6.01993System tools such as DoubleSpace, Anti-Virus, Defragmenter, MSBackup added
6.21993CHKDSK replaced with SCANDISK, CD-ROM caching added
71995Supports long file names, part of Windows 9x.

Thursday, January 26, 2006

MS-DOS and The Command Prompt

Even though Windows has moved on since the days of MS-DOS many of the commands are still available to use in even the latest version of Windows.

The Command Prompt can be found on Windows NT/2000/XP by going to Start > Run and typing CMD and return. The interface has been designed to look like DOS of old, but it's simply a Windows application interpreting your typed commands. Prior to Windows NT/2000/XP you would have typed COMMAND to get the command prompt, Windows 95/98/Me actually had full versions of MS-DOS.

Many people still use the DOS-based EDIT program to create and modify batch files. To use it type EDIT at the command prompt.

I'll be looking at DOS commands in more detail as I work through the A+ objectives, The standard DOS commands are stored in the following directories depending on the version of Windows you're running.
  • \\WINDOWS\system32
  • \\WINDOWS\Command
  • \\WINNT\system32
Each command can have a number of switches to enable you to configure the actions of the command. You can find out more about a particular command by typing the command name followed by /?.

For example:

C:\>XCOPY /?

Copies files and directory trees.

XCOPY source [destination] [/A | /M] [/D[:date]] [/P] [/S [/E]] [/V] [/W]
[/C] [/I] [/Q] [/F] [/L] [/G] [/H] [/R] [/T] [/U]
[/K] [/N] [/O] [/X] [/Y] [/-Y] [/Z]
[/EXCLUDE:file1[+file2][+file3]...]

source Specifies the file(s) to copy.
destination Specifies the location and/or name of new files.
/A Copies only files with the archive attribute set,
doesn't change the attribute.
/M Copies only files with the archive attribute set,
turns off the archive attribute.
/D:m-d-y Copies files changed on or after the specified date.
If no date is given, copies only those files whose
source time is newer than the destination time.
/EXCLUDE:file1[+file2][+file3]...
Specifies a list of files containing strings. Each string
should be in a separate line in the files. When any of the
strings match any part of the absolute path of the file to be
copied, that file will be excluded from being copied. For
example, specifying a string like \obj\ or .obj will exclude
all files underneath the directory obj or all files with the
.obj extension respectively.
/P Prompts you before creating each destination file.
/S Copies directories and subdirectories except empty ones.
/E Copies directories and subdirectories, including empty ones.
Same as /S /E. May be used to modify /T.
/V Verifies each new file.
/W Prompts you to press a key before copying.
/C Continues copying even if errors occur.
/I If destination does not exist and copying more than one file,
assumes that destination must be a directory.
/Q Does not display file names while copying.
/F Displays full source and destination file names while copying.
/L Displays files that would be copied.
/G Allows the copying of encrypted files to destination that does
not support encryption.
/H Copies hidden and system files also.
/R Overwrites read-only files.
/T Creates directory structure, but does not copy files. Does not
include empty directories or subdirectories. /T /E includes
empty directories and subdirectories.
/U Copies only files that already exist in destination.
/K Copies attributes. Normal Xcopy will reset read-only attributes.
/N Copies using the generated short names.
/O Copies file ownership and ACL information.
/X Copies file audit settings (implies /O).
/Y Suppresses prompting to confirm you want to overwrite an
existing destination file.
/-Y Causes prompting to confirm you want to overwrite an
existing destination file.
/Z Copies networked files in restartable mode.

The switch /Y may be preset in the COPYCMD environment variable.
This may be overridden with /-Y on the command line.

Wednesday, January 25, 2006

History of the Operating System

The Sybex book I'm reading starts the operating systems section by looking at the history of the operating system. How Microsoft Windows and MS-DOS came into being and their evolution to what we use today. It also covers basic concepts of an OS and the origins of the early systems that would go on to influence every OS built afterwards.

The subject matter of this whole chapter is however not covered by the A+ exam nor is it mentioned in the A+ objectives. It is worth reading, but since this site is intended for revision notes I don't see any reason to include anything on this section here.

Tuesday, January 24, 2006

To Certify or not to Certify?

If you are wondering whether to get A+ certified, why not read the articles below.

“The CompTIA A+ Certification Exam is considered the industry standard in terms of measuring a technicians hardware and software knowledge. Those possessing the certification are more likely to receive higher salaries and 85% of these individuals choose to further their careers. By adding more certifications to your portfolio the career paths become even more valuable and diverse.”

Read more here: Benefits of the CompTIA A+ Certification

“My experience with employers in regards to the A+ certification thus far has been that most employers know what the certification is and relish the fact that you have one. While this is a 50/50 coin toss, I can say from my experience that having the CompTIA A+ certification is an advantage. Not only is it a great entry-level moral booster when preparing for further educational and career moves, it will always put ahead of your non-certified competitors in the job market.”

Read more here: Walking The Talk Of CompTIA A+ Certification

Monday, January 23, 2006

A+ Operating System Exam Weightings

Below is a table from the CompTIA's examination weighting for the Operating System exam. This was taken from the 2003 objectives available from the CompTIA A+ site.
Notice how little knowledge is needed of networks. I presume this is due to the existance of the Network+ certification.

Topic% Of Examination
1.0 OS Fundamentals28%
2.0 Installation, Configuration and Upgrading31%
3.0 Diagnosing and Troubleshooting25%
4.0 Networks16%
Total100.00%