What is the difference between serial and random access

The location of the record within the file therefore is not a factor in the access time of the record. As such, random files are also known in some literature as direct access files. To create and maintain a random file, a mapping function must be established between the record key and the address where the record is held.

If M is the mapping function, then. There are various mapping techniques. Some involve using the key field to directly map to the location with the file, while others refer to some lookup table for the location. However, the more common method is to employ a hash function to derive the address. Hashing is the process of transforming the key value of a record to yield an address location where the record is stored.

This access method is the most primitive one. Example: Compilers usually access files in this fashion. There are three ways to access a file into a computer system: Sequential-Access, Direct Access, Index sequential Method. The only way to access records in a Sequential file, is serially.

A program must start at the first record and read all the succeeding records until the required record is found or until the end of the file is reached. Sequential files may be Ordered or Unordered these should be called Serial files. In computing, sequential access memory SAM is a class of data storage devices that read stored data in a sequence. All secondary storage devices which are capable of storing high volume data is referred to secondary memory.

It's slower than primary memory. However, it can save a substantial amount of data, in the range of gigabytes to terabytes. This memory is also called backup storage or mass storage media. Types of Secondary memory Mass storage devices:The magnetic disk provides cheap storage and is used for both small and large computer systems.

Two types of magnetic disks are:. Floppy disks. It's very fast compared to Hard Drives. Optical drives:This secondary storage device is from which data is read and written with the help of lasers. If end-of- file is reached before the desired number of byte has been read than EOFException is thrown. It is a type of IOException. A file that contains records or other elements that are stored in a chronological order based on account number or some other identifying data.

In order to locate the desired data, sequential files must be read starting at the beginning of the file. The terms random access and sequential access are often used to describe data files.

A random - access data file enables you to read or writeinformation anywhere in the file. In a sequential - access file , you can only read and write information sequentially , starting from the beginning of the file. A collection of records pertaining to one of the main subjects of an information system, such as customers, employees, products and vendors.

Master files contain descriptive data, such as name and address, as well as summary information, such as amount due and year-to-date sales. See master data management. Random access means you can move to any part of a file and read or write data from it without having to read through the entire file. Years ago, data was stored on large reels of computer tape. The only way to get to a point on the tape was by reading all the way through the tape.

A sequential file is a sequence of records. The records may or may not be kept in sorted order in the sequence. A record of a file is not necessarily declared to be of type structure. Elements stored in an array can be accessed both sequentially and randomly. Magnetic sequential access memory is typically used for secondary storage in general-purpose computers due to their higher density at lower cost compared to RAM, as well as resistance to wear and non-volatility.

What is the difference between a sequential access file and a random access file?