IBM System32 floppy ch8 free download

File name System32_floppy_ch8.txt

Subject: IBM System/32 Functions Reference Manual -- Chapter 8: Diskette drive functions Date: Sat, 7 May 2005 15:00:32 +0200 IBM32DSK.WS4 ------------ - Chapter 8 of the "IBM System/32 Functions Reference Manual" IBM Document GA21-9176-1 Second Edition: May 1975 (Retyped by Emmanuel ROCHE.) Chapter 8. Diskette drive functions ----------------------------------- The IBM System/32 diskette drive has a single head for reading and writing. The diskette supports two primary system functions: - Data interchange, using the IBM diskette for standard data interchange. - Storing data from the disk to save it for future use, then loading it back into the system at a later time when needed for a job. Physical characteristics ======================== Only one side of the diskette is used. The diskette surface is divided into tracks. Each diskette surface contains 77 tracks; track 00 is the outside track and track 76 is the inside track. Figure 8-1. Standard interchange diskette surface recording arrangement (not "retyped") Of the 77 tracks, only 75 are normally used. Track 00 contains the volume label; tracks 1-74 are primary tracks used to contain data records. Tracks 75 and 76 are available for data storage in the event that one or two of the primary data tracks become defective. For standard data interchange, each track is divided into 26 sectors (Figure 8-1). Each sector is 128 bytes long, so it is possible to store 242,944 bytes of information on tracks 1-73. Data can be stored on track 74 of a diskette in the standard data interchange format, allowing for the storage of 246,272 bytes of data on the diskette, if the data on track 74 is to be read only by a System/32. On diskettes in the extended format, track 00 is divided into 26 sectors, but each remaining track is divided into eight 512-byte sectors, making it possible to store 303,104 bytes of information on tracks 1-74. The data stored in each sector is called a record. Therefore, because the diskette is formatted into tracks and sectors, each record on the diskette has a definite address consisting of a track number and sector number. This address is recorded at the record's physical location on the diskette. Diskettes that contain prerecorded record addresses are known as initialized diskettes; each record consists of an ID field and a data field. Rotational speed of the diskette drive is 360 +/- 2.5% RPM. The nominal data transfer rate of the diskette drive is 31,250 bytes per second. The diskette drive reads 128-byte records from a diskette and writes 128-byte records to a diskette at the following rates: Using diskettes in the Using diskettes in the Standard interchange format Extended format Reads Up to 3,400 records per minute Up to 4,100 records per minute Writes Up to 1,800 records per minute Up to 2,200 records per minute Record format ========