Introduction The Difference Between Primary and
Secondary Storage
Secondary storage devices hold files that are not currently being used. For a file to be used it must first be copied to main memory first. After any modifications files must be saved to secondary storage. It is advisable to save your data files at the regular intervals as you work on them as data can be lost unexpectedly because of various reasons like interruption in power supply, memory management problems, freezing keyboard, etc.
As secondary storage media can be damaged and files on them become corrupted, it is suggested to make back-up copies of valuable files on a regular basis. Lots of people skip the last but very important step in the backup procedure - check that the backup copy of files is not damaged.
The Difference Between Primary and Secondary Storage.
Primary storage is volatile: when the power is off, all contents of RAM are lost. That is why data from RAM is saved as files on secondary storage which is non-volatile and almost permanent (It wears out eventually or becomes out of dated technology)
Size. Secondary storage is virtually infinite: when you run out of space on one disk, you use another. On the contrary there is a limited amount of RAM that can be accessed by the CPU. Some programs will not run on a particular computer system because there is not enough RAM available.
- RAM chips are located on the motherboard so the distance the electrical signals have to travel from the CPU to RAM or in the opposite direction is much shorter compared to the distance between the CPU and secondary storage devices. The shorter the distance, the faster the processing.
- Also working with the secondary storage involves mechanical operations like spinning
The various levels of memory from registers to cache, to primary, to secondary storage have decreasing cost and speed and increasing capacity.
| Type of Memory | Access Speed | Capacity | Cost |
| Registers (inside the CPU) | Highest | Lowest | Highest |
| Cache | |||
| Primary storage | |||
| Secondary storage | Lowest | Highest | Lowest |
Secondary storage devices provide direct access to data or sequential access.
Direct access, also called random access, means that the system maintains a list of data locations and the required piece of data can be found quickly. The most common direct access storage is the disk.
The most popular types of disks today are floppy disks, hard disks and optical disks.
Sequential access means the computer system must search the storage device from the beginning until it finds the required piece of data. The example would be a magnetic tape where data is stored sequentially and can be processed only sequentially.
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