The number of records contained within a block of data on magnetic tape is defined by the

The correct answer is: C. blocking factor.

A blocking factor is the number of logical records that are grouped together to form a physical record on a magnetic tape. The blocking factor is specified by the user when creating a file on magnetic tape. The blocking factor affects the efficiency of data access on magnetic tape. A higher blocking factor results in more efficient data access, but it also results in larger files. A lower blocking factor results in smaller files, but it also results in less efficient data access.

The other options are incorrect.

• A block definition is a set of parameters that define the structure of a block of data on magnetic tape. The block definition includes the number of bytes in the block, the number of records in the block, and the format of the records.
• The record contain clause is a clause in a COBOL program that specifies the number of records that are contained in a block of data on magnetic tape.
• The record per block factor is a factor that is used to calculate the number of records that are contained in a block of data on magnetic tape. The record per block factor is calculated by dividing the number of bytes in the block by the number of bytes in a record.
• None of the above is a correct answer.