Details:

1) The magnetic card standard stipulated by ISO is divided into three tracks on the magnetic strip, and the length of data that can be written to each track is:

Track 1: Maximum 76 words. SS:ASCII 25H(%), this track can write all characters in the ASCII code 20H-5FH, including English and numeric characters.
Track 2: Maximum 37 words. SS:ASCII 3BH(;) This track can write 0-9 digits, and: < = >? Six symbols.
Track 3: Maximum 104 words. SS:ASCII 2BH(+), this track can write 0-9 digits, and:; < = >? Six symbols.
(2) ISO standards for magnetic cards
Some of the ISO standards for magnetic cards, especially those used in banking systems, are ISO7810, ISO7811-1 to ISO7811-6, ISO7812, ISO7813 and ISO15457. Among them:
ISO7810 standard: developed the physical characteristics of the magnetic card;
ISO7812 standard: developed the magnetic card recording technical standards;
ISO781-4 standard: developed a magnetic card read-only Track1 and Track2 recording technical standards;
Iso 781-5 standard: The technical standard for recording Track3 on magnetic cards that can be read/written;
ISO15457 standard: Developed the magnetic card physical standard/test method Track standard F / 2F technical standard;

(3) The physical structure and data structure of the magnetic card
Generally speaking, the magnetic tape on the magnetic card used in the banking system has three tracks, namely Track1, Track2 and Track3. Each Track records different information, which has different applications. In addition, there are also some applications that use only two tracks, or even only one Track. In the application system designed by us, all three tracks or two or one Track can be used according to the specific situation.