The difference between the three tracks of the magnetic card can be written

The three tracks on the magnetic card are generally encoded using the "bit" method. Depending on the track in which the data resides, 5 bits or 7 bits form a byte.

Track1 (IATA): The recording density is 210BPI; you can record 0~9 digits and A~Z letters, etc.; you can record up to 79 digits or characters (including start terminator and check digit); each character (one Byte) consists of 7 bits.

Since the information on Track1 can be represented not only by the numbers 0 to 9, but also by the letters A to Z, the information on Track1 generally records the "marking" and "description" of the type and range of the magnetic card. Information. For example, in a bank card, Track1 records the user's name, the card's effective use period, and other "marker" information.

Track2 (ABA): Recording density is 75BPI; can record 0~9 digits, can't record A~Z characters; can record up to 40 numbers in total (including start terminator and check digit); each data (one word) Section) consists of 5 bits.

Track3 (THRIFT): The recording density is 210BPI; you can record 0~9 digits, you can't record A~Z letters; you can record up to 107 numbers or characters (including start terminator and check digit); each character ( One byte) consists of 5 bits.

Since the information on Track2 and 3 can only be represented by the numbers 0 to 9, etc., the letters A to Z cannot be used to represent the information. Therefore, in the bank card, Track2, 3 is generally used to record the user's account information, payment information, etc. Etc. Of course, there are some special information requested by banks.

In actual application development, if we want to represent information other than numbers in Track2 or 3, such as "ABC", etc., it should generally be mapped using an ASCII table according to international standards. For example, to record the letter "A" on Track2 or 3, you can use the ASCII value "0x41" of "A". “0x41” can be represented by two data in Track2 or Track3: “4” and “1”, namely “0101” and “0001”.

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