Class Summary for 1/17/2008 - DOS, file system, and cell hardware

Cell Phone Hardware
We reviewed the three hardware parts of a computer: the central processor unit, memory, and input/output. In a cell phone, we said there was memory and a CPU. There is also a display (output), keyboard (input), bluetooth (both input and output), headphone/microphone jack (both input and output), USB port(input and output), speaker (output), camera (input), microphone (input), and SIM card storage (input and output). Phone numbers, cell phone activation, and other info are stored on the SIM card. Also, SIM cards may be moved from phone to phone.

File System
State: There are several kinds of file systems like CDFS for a CD as well as FAT and NTFS for a hard drive in a computer. Flash disks and floppy drive disks use the FAT file system. A file system describes the way information is organized on a storage disk.

Elaborate: In FAT, CDFS, and NTFS file systems, information is organized in an upside down tree structure. The root, signified by a backslash or \, is at the top. Below the root, there may be sub-directories (also known as subfolders) and files. The sub-directories themselves may contain additional sub-directories and files below them. When we travel through the file system, we name each sub-directory from the root down. When we name the root and each sub-directory below it, it is called a fully qualified path name, abbreviated to FQPN. The current directory is called dot and is symbolized by a period or . The parent directory, one level up, is symbolized by two periods or .. and is called dot dot.

Exemplify: If I am looking for My Documents, the fully qualified path name would be \Documents and Settings\dclingingsmith\My Documents. In this path name, the first backslash is the root, the next lower subdirectory under root is Documents and Settings, below (or inside of) Documents and Settings is another subdirectory called dlclingingsmith. Finally, below the dclingingsmith folder is my My Documents folder. Inside My Documents, I would find my files.

Illustrate: A file system is like an upside-down root system of a tree. Moving through the different levels of the file system is like climbing from branch (or root) to branch in this upside-down tree.

DOS Commands
State: DOS commands are commands typed individually into a Microsoft Windows computer. They are the original commands that existed before Microsoft invented Windows 98 or Windows XP.

Elaborate: There are lots of DOS commands. To run them in Windows XP, a DOS window must be opened. To open a DOS window, go to Start --> Run. A run window will appear. In the run window, type the command cmd. Once the DOS window appears, commands may be entered. The two commands we have used are cd, which stands for change directory and dir which lists the contents of a directory. To exit the DOS window, type the command, exit. For a complete list of DOS commands, see this web site: http://technet.microsoft.com/en-us/library/bb491071.aspx

Exemplify: To list the contents of a directory, I would type dir. To change to the root, I would type cd \. To change to my My Documents folder, I would type: cd \Documents and Settings\dclingingsmith\My Documents.

Illustrate: DOS commands are very powerful. They are much like hidden commands. That is, I can go to My Computer and click on the My Documents icon to get to my Word or Excel files. Or, I can use DOS with the cd command also.