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IBM's first magnetic tape data storage devices, introduced in 1952, use what is now generally known as 7 track tape. The magnetic tape is 1/2" wide and there are six data tracks plus one parity track for a total of seven parallel tracks that span the length of the tape. Data is stored as six-bit characters, with each bit of the character and the additional parity bit stored in a different track. These tape drives were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long U-shaped loops of tape. Between active control of powerful reel motors and vacuum control of these U-shaped tape loops, extremely rapid start and stop of the tape at the tape-to-head interface could be achieved. When active, the two tape reels thus fed tape into or pulled tape out of the vacuum columns, intermittently spinning in rapid, unsynchronized bursts resulting in visually striking action. Stock shots of such vacuum-column tape drives in motion were widely used to represent "the computer" in movies and television. ==Technical details== ; Density : Initial recording density was 100 characters per inch. Later models supported 200, 556 and 800 characters per inch. ; Inter-record Gap : A gap (initially one inch, later 3/4 inch) between records allowed the mechanism time to start and stop the tape. ; Latency : There was only a 1.5ms delay for the stopped tape to reach its full reading or writing speed. ; Markers : Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. ; Write protection : A removable plastic ring in the back of the tape reel was inserted to indicate writing should be permitted. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IBM 7 track」の詳細全文を読む スポンサード リンク
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