Computer Storage and Capacity Calculation

Disk Capacity Calculation

• Sector capacity is calculated by dividing the sector size by the record size.
• Track capacity is the product of sector capacity and the number of sectors per track.
• Cylinder capacity is the product of track capacity and the number of tracks per cylinder.
• Drive capacity is the product of cylinder capacity and the number of cylinders needed.

Calculating Disk Space

• To store 300,000 128-byte logical records, the required disk space is 41.25 MB.
• To store 300,000 120-byte logical records, the required disk space is 41 MB.

I/O Operations

• The processor sends a set of information to the DMA module to initiate a read or write operation.
• In interrupt-driven I/O, the processor issues the I/O command, and there are two possibilities: the processor waits for the operation to complete or the processor continues executing other tasks.

Objectives of I/O Facility Design

• Two paramount objectives of designing the I/O facility are: (brief explanation needed)

Disk Characteristics

• A disk with 512 bytes/sector, 96 sectors/track, 110 tracks/surface, and 8 usable surfaces has a surface capacity of 42,240 records.

Cylinder Calculation

• To store 50,000 fixed-length records of 256 bytes each, the required number of cylinders can be calculated.

Multiple Choice

• The correct answer for the category of external devices suitable for communicating with the computer user is D. human readable.
• The correct answer for the type of data transferred by a stream-oriented device is D. data.
• The correct answer for the component that need not spend time waiting for an I/O operation to be performed in Interrupt-driven I/O is A. processor.
• The correct answer for the technique that smooths out peaks in I/O demand is C. Smoothing.