title: How are applications and data accessed by the CPU from RAM
body: <p>I am having a bit of trouble understanding how applications and data are accessed by the CPU from RAM after the application has been loaded into RAM and a file opened (thus data for the file also stored in RAM).</p>
  
  <p>By my understanding, a CPU just gets instructions from RAM as the program counter ticks or carries out tasks after an interrupt. How then does it access the application and data. Is it that it doesn't and still just gets instructions (for example to load a file on the hard drive to be opened in the application) and processes any requests made by the application which are stored in RAM as instructions thereafter (like saving a file). Or does the application and data relating to an opened file (for example) just stay in RAM and not get accessed by the CPU at all. </p>
  
  <p>Similarly, after reading an article, it said that a copy of the operating system is stored in RAM. The CPU can then access the operating system. (I thought the CPU just worked with instructions from RAM). How does it then communicate with the operating system and how are interrupts sent to the CPU, from the copy of the OS in RAM or from the OS in the hard drive.</p>
  
  <p>Sorry if this is really confusing, alot i didn't understand.</p>