1. TheTeacher Computing Data Storage Computing

2. TheTeacher Computing Primary Storage One of the fundamental properties of a computer is that it can store data. Primary storage is also known as memory. The CPU can directly access data stored in memory. Access to data in memory is very fast.

3. TheTeacher Computing Primary Storage There is a small amount of memory in the CPU itself. Data is stored in registers Each register holds a word of data (typically 32 or 64 bits) Registers are the fastest forms of data storage.

4. TheTeacher Computing RAM Cache (Cache memory) RAM cache memory is a chip of memory commonly built into the motherboard. Speed is somewhere between super-fast registers and slower RAM. Used to speed up the processing. Stores frequently needed data. Smaller capacity than RAM, but larger capacity than registers

5. TheTeacher Computing RAM (Random Access Memory) RAM is connected to the CPU by an address bus and a data bus. Data access is slower than cache, …but capacity is larger. RAM is volatile. The data is lost when the power is switched off. RAM is used for temporary storage of data and programs. Data can be changed.

6. TheTeacher Computing ROM (Read Only Memory) ROM is non-volatile – The data is not lost when the power is switched off. Stored data can be read but not changed. ROM is used for permanent storage of data. Example : The BIOS is stored on ROM. This is the program that boots up the computer. ROM memory chips are often found in embedded devices

7. TheTeacher Computing Secondary Storage Secondary storage is not directly accessible by the CPU. Data is input from and output to a storage device. Storage capacities are considerably larger than main memory. Access speeds are much slower than main memory.

8. TheTeacher Computing Comparative Speeds (Fastest first) Primary storage –Registers –RAM Cache –Main memory (RAM) Secondary Storage

9. TheTeacher Computing Types of Secondary storage Magnetic Tape Magnetic Disk (Eg Hard Disk) Optical Disk (Eg CD, DVD) Flash Memory

10. TheTeacher Computing Magnetic Tape Large capacity - Tape cartridges can store hundreds of gigabytes of data. Inexpensive means of data storage. Slow access times. Commonly used for backup of data.

11. TheTeacher Computing Magnetic Disc Hard disks are the most commonly used secondary storage media. Data is stored on rotating platters of magnetic material and read by a swivelling arm. Relatively fast access speeds Sealed unit so durable. Some drives are external, so can be connected to different computers. 500 Gb drives are available.

12. TheTeacher Computing Optical Disks CDs and DVDs use laser technology to read/write data Low cost media Portable media External or internal drives are available.

13. TheTeacher Computing Flash Memory Used on memory cards and USB flash memory drives. Memory cards are used in digital cameras and mobile phones Flash memory drives can be connected to a USB port of a computer. Portable