Computer Fundamentals

Computers can store information in either human-readable format or in machine readable or binary format.  If you try to print, or open a binary format file, you will see a series of happy faces and other symbols that mean nothing to you.  Within binary files, there can be open standards or proprietary formats.  Different word processors use different symbols to indicate formatting--thus Microsoft Word may or may not be able to read and correctly format a Word Perfect file.  For complete portability you should use a universal format like ASCII (text only) or HTML (allows formatting).

Computers store all data as a series of ones and zeros.  For numbers this leads to a fundamental difference between integers (the counting numbers) and real or floating point numbers.  Integers can be stored exactly with a series of ones and zeros, but real numbers must be approximated.  Computers store reals as an exponent and mantissa, which allows precision to a given number of decimal places depending on the number of bytes used.  Real arithmetic requires much more computer processing power than integer arithmetic, which is why computers typically has a math coprocessor or floating point unit (FPU) designed to perform the calculations in hardware.  Real numbers generally follow the standards of the IEEE (The Institute of Electrical and Electronics Engineers), which provides both 4 byte and 8 byte floating point types.

Byte order: computers use two fundamentally different ways to store the bytes for numbers, LSB and MSB for whether the least significant byte or the most significant byte comes first.  These are also called Big-endian (MSB first) and Little-endian (LSB first), and Windows PCs use the LSB first, the opposite order from Macs and most Unix machines.  This requires that binary files often must be byte-swapped before use if you have "wrong-endian" data.

Hardware:

• Parallel port: used for the printer, external ZIP drives, scanners, and cameras.  These use a 25 pin connector on the PC, and a slotted connector on the printer.
• Serial port: used for external modems, mice, and connecting instruments.  Most newer ports use a 9 pin connector, but some older ones have a 25 pin connector.
• USB: Universal Serial Bus: a faster and better connection that lets you change components on the fly.  The computer should recognize the peripheral and not require re-booting.  The connectors are small rectangular plugs.
• SCSI: (Small Computer System Interface): less common standard for computers which requires interface cards that look like large printer connectors.

Software:

• Operating system: the computer code that lies between the hardware and the applications programs a user wants to run.  Examples include Unix, Linux, Windows 98 or NT.
• Application program: something a user wants to run, such as a word processor, spreadsheet, or web browser.
• Language: a tool for programmers, which has syntax for telling the computer what to do.  The language lets the programmer deal at a higher level than the machine, which ultimately understands only machine language.  Assembly language uses simple codes to represent instructions, while higher level languages like Basic, Pascal, Fortran, C or C++ are almost readable.
• Dynamic link library (DLL): part of an executable program that resides in a separate file, and is joined with the main program for execution.  DLLs can be shared among multiple programs, and can be written in different languages.

Utility Programs with Windows:

• Notepad: reads small ASCII files.  If you try to read too large a file, it will use WordPad.
• WordPad: reads ASCII files, and Microsoft Word format.
• Hyperterminal: connect with a modem, or direct to the serial port.  This provides a good way to check instruments that talk via the serial port.  You must select the correct serial port, and the port parameters (baud rate, number of stop bits, and the parity), which are set by your instrument.

Computer displays come in two types:

• Raster: pixel oriented, with all text and graphics made up of individual dots.  Almost all common computer devices are raster, including monitors, laser printers, ink jet printers, and dot matrix printers.
• Vector: text and graphics are composed on line segments.  The only common vector devices are pen plotters, which physically move a pen across the paper.

Compression:  making the image smaller for faster downloads on the WWW or less storage space required.

·        Lossy:  the original image cannot be fully restored; some information is lost.  “Good” compression makes small files with very little obvious degradation in quality.

·        Lossless: the original image can be restored; no information will be lost.  In some case the compressed image could be larger than the original.

Image formats:

·        BMP: the standard Windows Bit Map Picture format.

·        GIF: Graphics Interchange format, pioneered for Compuserve.  Compressed format.  Lost some popular support when its compression method was patented, making users liable for royalty payments.  Only allows 256 colors.

·        JPEG: Joint Photographic Experts Groups, a compressed format in the public domain.

·        TIFF: Tagged Image File Format, with both compressed and uncompressed variants.  A special version (GEOTIFF) can contain ground coordinates associated with the image, making it applicable for satellite or map data.

Movie formats:

·        MOV: the Apple QuickTime format.  Apple has a viewer available for free download for Windows. Compressed format.

·        GIF: Graphics Interchange format, pioneered for Compuserve.  This movie format can only use 256 colors and does not support sound. Compressed format.

·        AVI: AudioVisual Interleaved, the native Windows format.  These can be uncompressed or compressed; if compressed, the viewing computer must have the correct codec to decipher the file, and often this will not be the case.

·        MPEG: Motion Picture Experts Group, a compressed format.

Sound formats:

·        WAV: Windows Audio Visual, basically a digital tape recorder format.  Setting control the quality of the sound, and files can become very large very fast.

·        MID: MIDI, where only the notes and instruments used are stored.  Very compact for instrumental music, but cannot store vocals or sound effects.

·        MP3: current MPEG format for sound only, with very good compression.  Legal quagmire as people copy and post music illegally, but many struggling bands want to distribute their music to build up a following.

Data Storage Sizes:

·        Bit: the smallest element used by a computer.  In electrical terms it represents on/off; in mathematical terms, a 0/1.

·        Byte: eight bits.  The can represent 2⁸ (256) distinct values, or numbers from 0 to 255.

·        Kilobyte: 2¹⁰ (1024), often loosely considered to be 1000.

·        Megabyte: 2²⁰ (1024²=1,048,576 ), often loosely considered to be 1,000,000.

·        Gigabyte: 2³⁰ (1024³=1,073,741,824), often loosely considered to be 1,000,000,000.

·        Terabyte: 2⁴⁰ (1024⁴=1,099,511,627,776), often loosely considered to be 1,000,000,000,000.

Text formats

·        ASCII: American Standard Code for the Interchange of Information.  A code that uses 128 values to transfer text data between computers.  These include the alphabet (upper and lower case), 10 digits, punctuation marks, and some control characters (tab, beep, line return, escape).  Since computers generally use bytes for efficient storage, IBM extended this character set to include some international characters and box drawing.  The extra 128 characters should be available on most Windows machines.

·        HTML: Hyper Text Markup Language, the mainstay of the WWW.  An ASCII coding that using special codes (<B> and </B> to start and stop boldface, for instance) to allow the transfer of formatting information in files.  Standard word processors use proprietary codes for formatting that usually cannot be readily transformed to other machines.

Color formats

·        RGB model: computers and televisions used a red-green-blue model for colors; the monitors use three electron guns.

·        CYM model: printers use a cyan-yellow-magenta model.  Cyan is a light blue (the mixture of green and blue), yellow mixes red and green, and magenta is purple (the mixture of red and blue).  Mixing all three should give black, but this generally looks bad and most printers also include a fourth ink, black.

·        16 color: the 16 colors can be selected from the 16 million the monitor can display.

·        256 color: the 256 colors can be selected from the 16 million the monitor can display, although in some cases Windows forces about 30 of the colors to be its standard choices.

·        15 bit color: uses 5 bits for each color.

·        16 bit (high color): since storage must be in 8 bit (or byte) increments, 16 bit color is common.  This does not divide evenly into three colors, but blue generally contains much less information than red or green and this provides very acceptable results.

·        24 bit (true color): 8 bits for each color, or a total of 16,777,216.  This is the limit that can be displayed by most monitors.  Most users cannot differentiate anywhere near this number of colors, and cannot distinguish this mode from 15 and 16 bit modes.

Storage media:

·        Floppy disks: store 1.44 MB.

·        Zip disks: original version stores 100 MB; newer version larger.  This has become a kind of standard because so many have been sold.  You can get internal models, which are faster, or external models, which are easy to transport and hook up to the computer via the printer port.  Made by IOMEGA.

·        JAZZ disks: stores 1 GB.  Only available in internal models.  Made by IOMEGA.

·        CD-ROM: store 650 MB, or 74 minutes of CD quality music (so about 9 MB/minute)

·        CD-R: CD-Recordable; these can be “burned” once.  The media cost about $1 each for 650 MB, so media cost is negligible.

·        CD-RW:CD-Rewrite; these can be written over.  They cost $10 or so each, and thus are a lot more costly than plain CD-R.

·         DVD: store the equivalent of 5-6 CD-ROMs.  The encryption system for movies has just been cracked in Scandinavia, setting off a legal battle about whether you can post a link to the location where the software is available.