Depending on the type of data memory or the data structure, a distinction can be made between different types of access. The basic types of access are:
- Read access
- The data is read, but not changed.
- Write access
- New data is written into the data memory or the data structure.
- Sequential access
- Access happens in a specific order.
- Random access
- Access can take place in any order.
RAM in a computer
As memory access here is called from the reading or writing of memory contents or in the memory of the computer . Because there are different types of memory, the access methods also differ. The basic principle, however, is usually as follows (the description refers to read access , but write access works in the same way):
The memory access is initiated by a program that knows the address of a specific memory content. In order to cause access to the relevant memory cell, the address is first loaded into the memory address register of the processor . This has the effect that the address is also applied to the address bus . When the processor now carries out its read access to the main memory, the correct memory cell is read out using the address specified on the address bus and its content is transferred via the data bus into the memory content register of the processor. The requested content of the memory cell is then available for further operations and the memory access is ended.
Hard disk access
Hard disks only address entire data blocks or sectors , which means that file systems also have this address granularity. Even if less data is required, at least the entire block must be read from the hard disk into the main memory.
- Jürgen Plate, FH Munich: Introduction of data processing systems - 7th storage unit (main memory).