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Primary Storage

Primary Storage. Memory. This is located on the motherboard so that data can travel quickly to and from the cpu. Data can be stored in the memory and it can be accessed to be read from, written to or processed. There are several types of computer memory:

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Primary Storage

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  1. Primary Storage

  2. Memory • This is located on the motherboard so that data can travel quickly to and from the cpu. • Data can be stored in the memory and it can be accessed to be read from, written to or processed. There are several types of computer memory: • RAM (Random Access Memory) or Main Memory • ROM (Read-only Memory) • Hybrid Memory

  3. RAM – Random Access Memory • These memory chips store the temporary operating instructions for the computer, its programs and the data. The CPU receives the instructions and data to perform its job from RAM. • This memory serves several functions: • A working storage area which holds data currently being processed. • A working storage area where output data can be held before it is transferred to the printer or some other output device. • It would hold the program currently being executed.

  4. Advantage The computer can access data very quickly from RAM. Disadvantage It is volatile – the data held in RAM is lost when the computer is turned off or malfunctions. N.B. It is important to store data on a storage device, so that data can be stored permanently.

  5. ROM – Read-only Memory • This is an integrated circuit programmed with specific input/output instructions for the computer. These instructions can be read, but they cannot be changed or altered (non-volatile). • There are five basic ROM types: • ROM • PROM • EPROM • EEPROM • Flash Memory

  6. Advantages and Disadvantages of ROM Advantage The data stored is permanently Disadvantage The data stored cannot be easily modified or altered.

  7. PROM – Programmable ROM • Characteristics: • Contents can not be changed once PROM is programmed. • If data is to be changed, the device must be discarded. • Blank PROMs are inexpensive • More fragile than PROMs • Known as one-time programmable (OTP) devices, • i.e., can only be programmed once. • EPROM – Erasable and programmable ROM – used to store small amounts of data that must be saved when power is removed • Characteristics: • Programmed in the same manner as PROM • Can be erased and reprogrammed repeatedly • To erase, expose to a strong source of ultraviolet (UV) light. This would reset the chip to its initial state • When erasing, the entire chip has to be erased, not in part. • More expensive than PROMs • Very essential part of testing and developing applications.

  8. Hybrid Memory • There are two hybrid devices, EEPROM and flash. They are used to store code. These devices combine the features of both RAM and ROM. • EEPROM – Electrically Erasable and Programmable ROM • Characteristics: • Similar to EPROMs internally • Can be erased electrically, and in part • Data can be erased and rewritten • Data remains on the device forever, unless electrically erased. • Flash Memory – USB (Universal Serial Bus) • Characteristics: • Is a type of EEPROM, everything is electrical instead of mechanical • It is used for easy and fast storage of information in devices such as digital cameras and home video game consoles • It stores large amounts of data • It is low cost, non-volatile, fast (to read)

  9. Definitions to know: • Bit – Short for Binary digIT and it is a single unit of information that can have a value of either ON or OFF. • Byte - A byte is a set of 8 bits that represent a single character. It is a unit of measuring the computer data storage capacity. • Kilobyte (Kb) – 1,024 bytes or characters • Megabyte (Mb) – 1,048,576 (about one million) bytes or characters • Gigabyte (Gb) – 1,073,741,824 (about one billion) bytes or 1024 Mb • Terabyte – one trillion bytes • Word – the largest amount of data which can be accessed at the same time. • Word size – the number of bits which can be transferred in a word

  10. Secondary Storage

  11. Secondary Storage • This is also known as auxiliary storage and is all data storage that is not stored in the computer’s primary storage or memory. • Characteristics: • Saves data and programs for later use • Each secondary storage device or medium requires its own drive. • Secondary storage is non-volatile • It is less expensive than primary storage • Uses devices and media • It is different from primary storage in that it is not directly accessibly by the CPU.

  12. Storage Devices • Storage devices records and retrieves data, instructions and information from storage media. • What are some examples of Storage Devices you can think of? • Hard disk drive • Floppy disk drive • Compact Disk drive • Zip drive

  13. Storage Media • Magnetic Media - Most common and cheapest way to store data • Optical Storage • Includes Floppy disks, Diskettes, Zip disks, Hard disks and Magnetic tape • These devices include CD-ROM, CD-RW drives and DVD drives. Some storage devices allow data to be saved as well as read.

  14. Home Work • SCSI • IDE • SATA • For each: • 1) What the acronym stands for? • 2) What it means?

  15. THE END

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