The CPU and Memory

The CPU and Memory

1. Stands for Central Processing Unit.

   • Core of the computer- the brain
   • Processes all data & executes instructions
   • Two main components
     • The Control Unit (CU)
       • Controls hardware and software devices. Perform fetch, decode and execute cycle.
     • Arithmetic and logic unit (ALU)
       • perform all arithmetic and logical operations, e.g. calculations and comparisons
   • communicates between the input and output device and the computer's memory
   • receives all instructions in binary bit patterns, written in machine code
   • Fetch, decode and execute

2. Most computers have severe cache stores.

3. The cache memory stores the most commonly used instructions. This speeds up the fetch, decode, execute cycle because the data has already been fetched and decoded.

   • The CPU requests data from the cache. If available, the data is sent

4. When loading and using software, program instructions are loaded into the RAM. If more software is loaded, more memory space is used. After a while the memory space will run out and the RAM must overwrite previous addresses.

   • RAM is measured in megabytes (MB) or gigabytes (GB).
     • The larger the number, the faster a program will run. Increasing the amount of RAM will increase the computer’s overall speed

5. Flash memory is a non-volatile computer storage memory that can be electronically erased and rewritten. Flash memory’s proper name is EEPROM (Electrically Erasable Programmable Read-Only Memory).

   • used in SD cards, USB drives and solid-state drives
   • Flash Memory devices are easy to manufacture, can hold large amounts of data and have no moving parts.

6. Virtual memory is located on the hard disk and is used as storage for program/software instructions that will not fot into the RAM. If the Ram is full, content can be temporarily written to the hard disk and retrieved when required. This prevents the computer from slowing down.

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