An information storage device is a memory. Computer memory can be divided into two main groups – internal and external memory. The internal memory includes:
- Random access memory (RAM);
- cache memory;
- Permanent storage device (ROM).
The external ones include:
- hard drives;
- floppy disks;
- flash cards;
- Optical discs (CD or DVD).
The internal memory is usually volatile, and the external one is non-volatile, respectively, i.e. data can be stored in the internal memory only if there is power. Because of the different ways of using these types of memory, this separation occurs. External memory is intended for storing data and programs, while the internal memory is used when processing information by a computer (Fig. 4).
RAM (RAM, RAM) provides work with the software. From it, the processor and the coprocessor (a device that helps the processor perform complex mathematical calculations) take programs and source data for processing. The characteristic of RAM is the amount measured in megabytes (MB). RAM is available in the form of chips assembled into special modules: DIMM or the latest DDR and DDR2 modules. Each module can hold from 1 to 512 MB (Fig. 5).
Fig. 5. RAM module
Cache is used to speed up access to RAM, on high-speed computers, a special ultra-fast cache memory is used, which is located as if between the processor and RAM and stores copies of the most frequently used sections of RAM. When the microprocessor accesses the memory, the necessary data is first searched in the cache memory. Since the access time to cache memory is several times less than to regular memory, and in most cases the data required by the microprocessor is already contained in cache memory and the average access time to memory decreases.
All these types of memory are volatile, i.e. they are cleared when the power is turned off.
Permanent memory. Other names: ROM (Permanent Storage Device), ROM (Read Only Memory – read-only memory). Slow memory is necessary to start the computer when it is turned on. Non-volatile.