Computers Miscellany by George Hernandez

A miscellany of items pertaining to computers.

Computers
Databases
Programming
Miscellany

Computers

Major models:
- Create, Read, Update, Delete (CRUD). That corresponds roughly with the standard SQL statements: Insert, Select, Update, Delete (ISUD). The four basic functions of persistent storage. There are many other variants. One involving 3-letter words: Add, Get, Set, Cut (AGSC).
- Confidentiality, Integrity, Availability (CIA). Some folks make think it should be Confidentiality, Integrity, Availability, Accountability (CIAA). CIAA is the foundation of information security.
- Atomicity, Consistency, Isolation, Durability (ACID). ACID are properties that help ensure that database transactions are processed reliably. Relational databases (EG MySQL, MS SQL, PostgreSQL) are very good at ACID, while non-relational databases (aka NoSQL DBs. EG: BigTable by Google, Dynamo by Amazon, Cassandra by Apache) often sacrifice some ACID (especially consistency) for speed and volume.
- Client Server. Clients make requests to servers; Servers process requests and make appropriate responses to the client.
- Representational state transfer (REST). In the client-server model the resources at either the client or the server are said to have or make representations of resources. The resources may be in different states (EG: Processing, Waiting, Sleeping). The state of representations are transferred around so things happen as needed.
- Open System Interconnection Reference Model (OSI Reference Model or OSI Model). The OSI Model is an abstract description of computer communications, especially across networks. The OSI Model divides responsibilities into seven ordered layers: Application, Presentation/Syntax, Session, Transport, Network, Data Link, and Physical. Each layer can interact indirectly with a layer immediately next to it but a layer on one host also interacts with a peer layer on another host. Only the physical layer can communicate directly between computers. See also my article on OSI.
Mediums
- types, extensions, and apps.
- audio, video, picture formats.
- asx is wm playlist?
- foobar2000
  - Playlists: .fpl .m3u8 .m3u .pls
  - Uncompressed formats: wav aiff aif iff svx snd au voc
  - cue
  - ogg
  - musepack: .mpc .mp+ .mpp
  - mpeg-1 audio: .mp3 .mp2
  - mpeg-4 audio: mp4 m4a aac
  - flac: .flac .fla
  - monkey's audio: .ape .mac
  - wavepack: .wv
  - speex: .spx
  - modules: .xm .it .s3m .mod .mtm .umx
  - compressed modules: .mdz .s3z .itz .xmz .mo3
  - audio cd: .cda, audio cd
Two kinds of directory trees:
- Each directory object has an object list associated with it.
  - Selecting the icon or name of a file object shows its file content in the RHS pane.
  - Clicking the +/- icon of a directory object expands/collapses its object list in the LHS pane.
  - Selecting the regular icon of a directory object shows its object list in the RHS pane.
  - Selecting the name of a directory object shows its object list in the RHS pane. Note in some newer trees this also expands/collapses its object list in the LHS pane.
- Each directory object has an object list associated with it, as well as a file page.
  - Selecting the icon or name of a file object shows its file content in the RHS pane.
  - Clicking the +/- icon of a directory object expands/collapses its object list in the LHS pane.
  - Selecting the regular icon of a directory object shows its file content in the RHS pane. Note in some newer trees this also expands/collapses its object list in the LHS pane.
  - Selecting the name of a directory object shows its file content in the RHS pane. Note in some newer trees this also expands/collapses its object list in the LHS pane.
Check out the real start up in the registry: Local Machine, Software, Microsoft, Windows, Current Version, Run.
Operating Systems: histories and comparisons. Including BeOS, OS/2, FreeDOS, FreeBSD, and Mac.
Distributed (data, transactions, and parallel processing) can form the basis of natural neural networks that mimic the brain. Most data is free form (short term memory), but some lock into place (long term memory).
Domains
- NT domain models, eg single, master, multiple mater, and complete trust.
- 2000, 2003 domains
Control copyright by making blank DVDs expensive to all but those who have rights to reproduce.
RAM: SIMM, DIMM/SDRAM, RIMM/RDRAM
Presentation tier: page layout & page flow. Application tier: biz logic. Database tier: persistence.

Databases

2 pseudo tables in SQL Server used by triggers: deleted & inserted.
DSN & DSN-less
Notes from SQL Server DTS for WH's lecture by Greg Wilson at IMG on 2002-01-09.
- Use surrogate keys in place of real IDs from source.
- Source usu has relational structure whereas the WH will have star or snowflake structure.
- bcp is fastest but can only load from text file.
- DTS can move between 2 non-SQL Server stores too!
- VBS can be used in DTS.
- A DTS package can be saved as VB code which can then be used programmatically.
Table generating procedure.

Programming

Threading
- http://en.wikipedia.org/wiki/Thread_%28computer_science%29
- http://en.wikipedia.org/wiki/Threaded_code
Class based (classes and instances/objects. EG: Java, C++) vs. Proto-type based (EG: JS).
State. EG: stack, RPN, LIFO. EG: Sessions: ASP sessions vs cookies vs XML.
When coding, put in your delimiters first then fill in. It will help you not forget the closing delimiter.
Programming. General areas
- Data Types, including choosing, including .net and xml data types
- Error Checking
- Functions
- Time/Date
- String
Buy vs Build: Off-the-shelf/3rd party vs in-house development.
App Verbs from IIS: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE

Miscellany

An often overlooked feature in browsers is the Find feature. It is especially good if you are looking for something specific on any given page.
Most macro viruses can be avoided with the following steps. If you're opening an external Microsoft Office document, make sure you have the application's macro virus protection option turned on. This option is usually set by choosing the Tools menu, Options selection, and then General tab.
More frequently than not, it is quicker to retype something, than it would be to copy and paste it.
Watch out for viruses hidden with a ".shs" extension. The extension is hidden from view, even if not chosen to hide extensions of known file types.
5 steps of privacy policies: Notice. Choice. Access. Security. Enforcement.
Since American Express cards start with the digit 3, Visa with 4, MasterCard with 5, and Discover with 6, those numbers are often used to identify or validate the numbers. Cash is usually identified with the number 1 and checks with the number 2.
Ergonomics for working with a desktop computer:
- Keep monitor away from windows or perpendicular to windows to reduce glare.
- Line the top of the monitor screen with your eyes to reduce neck strain. This causes less stress on the neck muscles.
- Keep your feet are flat on the floor or on a foot rest.
- Your knees should be bent no more than 90 degrees.
- There should be enough clearance under the workstation to move your legs around freely and without hindrance.
- Your arms should be vertical at your sides. You should not have to hold your arms up at the shoulders.
- Your elbows should be at comfortable 90 degree angle.

Some cross platform approximations

Some Cross Platform Approximations
PC	Mac
Ctrl+z	Cmd+Opt+Esc or Cmd+.
Opt+Ctrl+Del	Cmd+Ctrl+Power
F2 at startup to modify BIOS settings	Shift+Power at startup to turn extensions off
Print Screen	Cmd+Shift+3
Alt+Ctrl+S	Cmd+Opt+Power rebuilds Desktop
Zap PRAM	Cmd+Opt+p+r+Power

Top tips for new computer users:
- Save often.
- Complete transactions. That is: Start a process and confirm its completion.
- Have anti-virus software.
- Close things that you aren't using now or very soon. Close applications, windows, tabs, etc.
- Do not have public computers save your user name and password.
- If there's a task you do often, there's a fair chance that there's a shortcut way to do it. See also my page on Microsoft Shortcuts. The most common shortcuts include:
  - Ctrl+C for Copy
  - Ctrl+X for Cut
  - Ctrl+V for Paste
  - Ctrl+Z for Undo
  - Ctrl+A for Select All
  - Ctrl+S for Save
  - Ctrl+F for Find. F3 is frequently "Find Again".
- Be wary of attachments. Only take simple things like images or text documents.
- More RAM.

Page Modified: (Hand noted: 2007-10-04 21:23:10Z) (Auto noted: 2010-07-15 15:51:43Z)