Bitmaps & Data Element Presence Quiz

1. In an ISO8583 primary bitmap, which bit indicates that a secondary bitmap follows?

Bit 0 Bit 1 Bit 64 Bit 65

2. You see a primary bitmap starting with byte `0x72`. Which fields from 1-8 are present?

Fields 1, 2, 7 Fields 2, 3, 4, 7 Fields 1, 3, 4, 7 Fields 2, 3, 6, 7

3. What is Field 1 (DE1) in ISO8583?

The primary bitmap The secondary bitmap (when present) Reserved for future use The message length header

4. To check if field 11 is present, you calculate byteIndex = (11-1)/8 = 1 and bitPosition = 7 - ((11-1)%8) = 5. What does this mean?

Check bit 5 of byte 0 Check bit 5 of byte 1 Check bit 11 of byte 1 Check bit 1 of byte 5

5. You're building an ISO8583 message with fields 2, 3, 4, and 70. What must be true about the bitmap?

It must be 8 bytes with fields 2, 3, 4, and 70 set It must be 16 bytes with bit 1 set automatically Field 70 cannot be included in a standard bitmap It must be 24 bytes (primary + secondary + tertiary)

6. A bitmap shows the hex bytes `80 00 00 00 00 00 00 00`. Which field is present?

Field 0 Field 1 (secondary bitmap indicator) Field 8 No fields are present

7. What's the difference between binary and hex-ASCII bitmap encoding?

Binary uses 16 bytes, hex-ASCII uses 8 bytes Binary uses 8 raw bytes, hex-ASCII uses 16 ASCII characters representing the hex They are the same thing Binary is for 1987 spec, hex-ASCII is for 2003 spec

8. You're debugging a parser that shows field 64 when it should show field 65. What's the likely bug?

Endianness issue with the bitmap bytes Off-by-one error: using 0-based instead of 1-based field numbering The secondary bitmap is missing The bitmap is hex-ASCII encoded

9. In the formula `bitPosition = 7 - ((field - 1) % 8)`, why do we subtract from 7?

Because there are 7 bytes in a bitmap Because ISO8583 uses MSB-first bit ordering within each byte Because field numbers max out at 7 To account for the secondary bitmap indicator

10. You receive a 16-byte bitmap where the first byte is 0x40. What does this indicate?

Only field 2 is present, and there's a secondary bitmap Field 2 is present, but there's no actual secondary bitmap since bit 1 is 0 This is invalid - if you have 16 bytes, bit 1 must be set The bitmap is corrupted

11. How do you set field 37 in a bitmap using Go?

bitmap[37] = 1 bitmap[4] |= (1 << 3) bitmap[4] |= 0x08 Both B and C are correct

12. Your parser suddenly fails with a new integration partner. The first 8 bytes of the bitmap look like: 37 32 33 41 34 34 38 31. What's happening?

The bitmap is corrupted The partner is sending hex-ASCII encoded bitmaps The partner is using 2003 spec with tertiary bitmap The byte order is reversed

13. What's the purpose of the tertiary bitmap in ISO 8583:2003?

To provide redundancy for error checking To enable fields 129-192 To support multiple messages in one transmission To replace the secondary bitmap in modern implementations

14. A message fails with 'unexpected end of message'. The bitmap indicated 15 fields but only 14 were found. What likely happened?

The bitmap has a bit set that shouldn't be A field was omitted from the data without clearing its bitmap bit The parser has a bug in field counting Any of the above could cause this error

15. Which fields commonly use the secondary bitmap in production messages?

PAN (DE2) and Amount (DE4) MAC (DE64 or DE128), Original Data (DE90), Private Use (DE127-128) MTI and Processing Code Secondary bitmaps are rarely used in production