LOGIC GATE REGISTERS BUSES
CU ALU & CU--- Main
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MEMORY
Memory is a form of electronic storage, it is used because if
the CPU had to constantly access the hard drive then I would operate very
slowly. But when the information is kept in the memory the CPU can then access
the files much more quickly.
In a computer the CPU accesses memory for data. it can either
come from permanent storage (hard drive) or input (keyboard etc), most data goes
in to Random access memory (RAM) first. Then the CPU stores pieces of data it
will need to access often, in the cache, and holds certain special instructions
within the register.
Memory within a computer plays a big role and with out it the
computer cannot work. lets look a typical computer start up sequence.
- You turn the computer on.
- The computer loads data from read-only memory (ROM) and performs a
power-on self-test (POST) to make sure all the major components are
functioning properly. As part of this test, the memory controller checks all
of the memory addresses with a quick read/write operation to ensure that
there are no errors in the memory chips. Read/write means that data is
written to a bit and then read from that bit.
- The computer loads the basic input/output system (BIOS) from ROM. The BIOS
provides the most basic information about storage devices, boot sequence,
security, Plug and Play (auto device recognition) capability and a few other
items.
- The computer loads the operating system (OS) from the hard drive into the
system's RAM. Generally, the critical parts of the operating system are
maintained in RAM as long as the computer is on. This allows the CPU to have
immediate access to the operating system, which enhances the performance and
functionality of the overall system.
- When you open an application, it is loaded into RAM. To conserve RAM
usage, many applications load only the essential parts of the program
initially and then load other pieces as needed.
- After an application is loaded, any files that are opened for use in that
application are loaded into RAM.
- When you save a file and close the application, the file is written to the
specified storage device, and then it and the application are purged from
RAM.
