Lecture Notes

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• ROM
• Byte
• Kilobyte
• Megabyte
• Gigabyte

• Opening, loading or reading a file
• Closing, saving or writing a file

• Review of last class.

• Three types of information are stored on secondary memory:
• Operating system (machine specific) can be thought of as basic housekeeping system.
• Unix; many different types of this operating system.
• Kernel (conceptual core of the operating system which is machine specific).
• Shell (neutral) therefore no machine specific characteristics.

• Application program; (Assist in completing a specific task). For example, Excel, Word, PhotoShop, AutoCAD, Form Z, etc.
• Data: any digital picture, text file, mp3, 3d model, spreadsheet, etc.

• All of the above examples are stored (represented) with the use of binary digits. The computer industry calls these binary digits or bits.
• To reiterate previous lecture, the logic behind all forms of data storage comes down to strategies of representation.
• Note: 8 bits = 1 byte
• 01101110 therefore 8 1’s and or 0’s in any configuration = 1 byte.
• Everything in binary is represented by a base two system. (2Ù ^x).
• One byte has 256 possible combinations. (2Ù ⁸ = 256).
• So each character and symbol of text is represented by one byte.
• (For more information see ASCII in the class glossary).
• "American standard code for information interchange.
• Common to all text.
• Documents ending in .txt are ASCII.

• Bits vs. bytes:
• Kilobyte » 1000 bytes = 1024 bytes…..2Ù ¹⁰
• Megabyte » 1,000,000 bytes =1,048,567…..2Ù ²⁰
• Gigabyte » 1,000,000,000 bytes.
• Terabytes
• Files
• Opening a file- copying from secondary memory to primary memory.
• Reading a file- copying from secondary memory to primary memory.
• Loading a file- copying from secondary memory to primary memory.
• Closing a file- copying from primary memory to secondary memory.
• Writing a file- copying from primary memory to secondary memory.
• Saving a file- copying from primary memory to secondary memory.