4.7

4.7

1. 4.7.1

   • internal components
     • Processor fetches, decodes and executes instructions
     • Main memory stores the instructions and data required by the processor
       • main memory is addressable memory
         • the memory is split into sections, with each section assigned an address
           • the contents of the memory at each address can be read or written by the proccesor
     • Address bus carries addresses from the processor to main memory and controllers
     • data bus carries data between the processor and the main memory and the controllers
     • control bus carries control signals between the processor and main memory and the controllers

2. 4.7.2

3. 4.7.3

4. 4.7.4

   • external devices
     • barcode reader
       • A laser scans across a series of black and white stripes
       • The amount of light reflected back indicates a black or white stripe
       • The width of the stripes represent numbers, which link to a product database
     • rfid
       • A small microcontroller with large antenna is embedded in a tag
       • Radio frequency induces enough current in the antenna to power the chip
       • The chip reads the data in the radio frequency and transmits a response