Storage devices
2 types of storage devices are in computers.
1. Primary Memory (Internal memory / Main memory)
Memory is volatile ( loose its data once the power is turned off) . it holds less memory than permanant storages.
Eg : RAM, ROM
1. Primary Memory (Internal memory / Main memory)
Memory is volatile ( loose its data once the power is turned off) . it holds less memory than permanant storages.
Eg : RAM, ROM
2. Secondory Memory (External memory )
Memory is non volatile (do not loose its data once the power is turned off). These devices may store data permanently or semi-permanently. Also used when the capacity of the internal storage is insufficient to keep the currently running programs and the data required- Also used when the capacity of the internal storage is insufficient to keep the currently running programs and the data required
Eg : Floppy Disk, CD-ROM, Hard Disk
Eg : Floppy Disk, CD-ROM, Hard Disk
RAM
Random Access Memory (RAM) is the main working memory. It uses to store current data and programs. RAM is a volatile memory which means that the memory is lost when you switch off the computer. More RAM results faster systems.ROM
Read Only Memory (ROM) is permanent storage of programs. The memory is only readable. ROM is a special memory chip from which existing software can be read but not written to.
Read Only Memory (ROM) is permanent storage of programs. The memory is only readable. ROM is a special memory chip from which existing software can be read but not written to. Programmable ROM (PROM) - Writing is after manufacture and the chip cannot be rewritten (written only once)
Electronically Programmable ROM (EPROM) - Writing is after manufacture and the chip can be erased using UV (Ultra Violet) light and re-written (writeble multiple times)
Electronically Programmable ROM (EPROM) - Writing is after manufacture and the chip can be erased using UV (Ultra Violet) light and re-written (writeble multiple times)
Electronically Erasable Programmable ROM (EEPROM) - Writing is after manufacture and the chip can be erased electronically and re-written
Most modern day motherboard BIOS chips are EEPROMs, hence we could do a BIOS upgrade
Cache Memory
The memory is about eight time slower than the speed of the modern day processors.
The performance of the processor would be reduced if the processor had to read data from the main memory all the time.
To avoid that problem, the cache memory was introduced. It is manufactured using SRAM technology.
Most frequently used instructions and programs are loaded to the cache memory. Cache comes as Level1 (L1), Level2 (L2) and Level3 (L3)
The memory is about eight time slower than the speed of the modern day processors.
The performance of the processor would be reduced if the processor had to read data from the main memory all the time.
To avoid that problem, the cache memory was introduced. It is manufactured using SRAM technology.
Most frequently used instructions and programs are loaded to the cache memory. Cache comes as Level1 (L1), Level2 (L2) and Level3 (L3)
Permanent Storage devices
Floppy disks
Floppy disk (disks, diskettes) are circular plastic disks. 3 ½ inch 2HD disks have 1.44 megabyte capacityHard Disks
A hard disk is an enclosed disk drive that contains one or more metallic disks. Enclosing the disk in a sealed container prevents entering of material that could cause a head crash. Hard disks have far more capacity than floppy disks do.
A hard disk is an enclosed disk drive that contains one or more metallic disks. Enclosing the disk in a sealed container prevents entering of material that could cause a head crash. Hard disks have far more capacity than floppy disks do.Hard disks come in 3 forms;
• An internal hard disk has more metallic platters sealed inside a container
• Hard disk cartilages can be removed when they are filled or transported
• Mini and mainframe computers use hard-disk packs, which are hard disks consisting of several platters in a stack.
• Hard disk cartilages can be removed when they are filled or transported
• Mini and mainframe computers use hard-disk packs, which are hard disks consisting of several platters in a stack.
Optical Disks
An optical disk is metallic dick that uses a laser beam for reading and writing. Four kinds are;
An optical disk is metallic dick that uses a laser beam for reading and writing. Four kinds are;- CD-ROM (Compact disk read only memory) – Cannot be written on or erased by user (read only). Used to distribute large databases, reference materials and software.
- CD-R (CD recordable) or WORM (Write once, read many) - can be written to one time, after which it cannot be erased by users but can be read many times without deteriorating.
- Erasable Optical disks – can be written on and erased and reused. Two basic types ; CD-RW (compact disk re-writable) and MO (magnetic optical)
- DVD (Digital versatile disk) – similar to CDs. Have a greater capacity of 4.7 gigabytes.
Magnetic Tapes
Magnetic tapes storage is mainly used to backup programs and data on disks. Two forms are;
Magnetic tapes storage is mainly used to backup programs and data on disks. Two forms are;- Magnetic tape streamers (backup tape cartridge units) consist of tape cartridges used to backup microcomputer hard disks.
- Magnetic Tape Reels, used to backup mini and mainframe computer storage. Run on magnetic drivers. (magnetic tape units)
Pen Drives (thumd drive/ Flash drive)
Pen drivers are fast becoming storage devices. These are very high capacity portable devices that can be plugged directly into the USB port which is available most modern day computers. These are also called flash drivers.
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