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Computer Fundamentals MSCH 233

Computer Fundamentals MSCH 233. Lecture 3. Units Of memory. Information is processed and stored in computers as Electrical Signals . It can be either ON or OFF.

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Computer Fundamentals MSCH 233

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  1. Computer Fundamentals MSCH 233 Lecture 3

  2. Units Of memory • Information is processed and stored in computers as Electrical Signals. It can be either ON or OFF. • All DigitalComputer uses binary notations to represent characters, where a character is defined as a letter, digit, or special symbol. • Binary notations has only two digits : 1 means ON and 0 means OFF.

  3. 1 : is used to denote the presence of an electrical pulse, signal , or a closed computer circuit permitting current to flow through. • 0:is used to denote the absence of such a signal or an open circuit that does not permit current to flow through

  4. Bits & bytes: • Each 1 or 0 is called a bit, as abbreviation for binary digit. • A bit is the smallest unit of data in a computer. • A group of 8 bits is 1 byte and can represent one character. Example: • 01000001 represent the letter A • 01000011 represent the Letter C

  5. ASCII Code • ASCII: American Standard Code for Information Interchange. • Most Computer uses 8-bit ASCII to represent binary. • There are 256 different way to combine 1 and 0 bits in a byte to represent a character. ASCII uses only 128 bytes.

  6. Kilobytes, megabytes, gigabytes We use Kilobytes (KB) , Megabytes (MB), and Gigabytes (GB) to describe the RAM memory, the storage capacity, and the size of any document. • 1 KB = 1,024 bytes • 1 MB = 1,024 KB • 1 GB = 1,024 MB

  7. Bits for pictures • Each dot on the screen is called a picture element or Pixel. • An Image are formed by combining large number of pixels. • Black and White Images and Text: • One bit in the memory (refresh buffer) represent one pixel on the screen and can be either ON ( Black) or OFF ( white) • Colored Images: • Each pixel is a combination of three primary colors: Read , green, and blue. • Use video card that convert the bits into visual signals • 1 bit of primary color can generate up to 8 colors ( 2^3) • 8 bits per primary color can generate up to 16.7 million ( 2^3) ^8

  8. Selection Criteria for a PC: Processor Speed Memory Capacity (Min and Max RAM) Hard Drive Size. Operation System Cost Monitor Disk Drives Technical Support Service Application Software Buying a computer:

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