Easytrieve Hex Values

Hexadecimal Literal Syntax

Prefix X, open single quote, hex digits 0-9 and A-F, close quote. X'00' is one byte of binary zeros. X'0000' is two bytes. Digits must be even count—each pair is one byte. No decimal point, no spaces inside quotes. Use hex literals anywhere literals are accepted: VALUE on DEFINE, assignment right-hand side, AND OR XOR mask operand.

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DEFINE FLAGS  W 2 B VALUE X'0000'
DEFINE SEED   W 2 P VALUE X'123F'
DEFINE SPACES W 2 A VALUE X'4040'
 
FLAGS = FLAGS OR X'0001'
SEED  = SEED AND X'FF00'

Bytes and Nybble Pairs

One byte equals eight bits, written as two hex digits. High nybble is left digit, low nybble is right digit. Packed decimal squeezes two decimal digits into one byte—the last nybble is sign. Binary X'80' sets high bit of one byte—128 unsigned or negative in signed byte interpretation depending on context.

Zoned vs Packed vs Binary Hex View

Zoned decimal N field storing 123 in three bytes EBCDIC often looks like X'F1F2F3' in hex—one zone and digit per byte in classic display format. Packed P two-byte 123 is X'123F'—compact. Binary B two-byte value 255 is X'00FF' on big-endian layout depending on field definition. Comparing hex dumps across types prevents declaring wrong type on FILE lines.

Bit Masks With Hex Literals

Logical assignment: receive = send AND mask clears bits where mask bit is zero. OR sets bits where mask is one. XOR toggles. Mask width should match field byte length—two-byte field uses four hex digits inside X'....'. Applying X'FF' mask to four-byte field only affects low byte—high bytes unchanged unless mask includes leading FFFF.

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DEFINE F1P W 2 P MASK HEX
DEFINE F2P W 2 P VALUE X'123D'
 
F1P = F2P AND X'FFFE'
F1P = F2P OR  X'000F'
F1P = F2P XOR X'FFFF'

AND X'FFFE' clears bit zero of low byte. OR X'000F' sets low four bits. XOR X'FFFF' inverts all sixteen bits in two-byte field. Test each step with DISPLAY HEX before production flag updates on interface records.

VALUE Initialization With Hex

VALUE X'123F' on DEFINE sets initial packed content at compile/load—not runtime file read. Useful for constant seeds, clearing flags to X'0000', or presetting test records in working storage. FILE fields do not use VALUE for file content—they read from dataset bytes. Distinguish initialization from assignment inside JOB logic.

MASK HEX for DISPLAY

DEFINE field MASK HEX formats numeric or character fields as hexadecimal on DISPLAY and some report contexts. Documentation notes display up to 50 bytes with HEX mask. Essential when teaching new developers packed layout—show X'123F' alongside edited decimal print from separate masked field.

EBCDIC vs ASCII Awareness

Mainframe EBCDIC digit zero is X'F0'; ASCII is X'30'. Literals and file data follow installation charset. Porting hex constants from PC documentation without conversion produces wrong character comparisons. IF STATUS EQ X'40' tests one EBCDIC space byte when STATUS is A 1—verify literal matches encoding.

Hex in Packed EVEN Fields

EVEN on P fields forces even digit count with leading zero nybble—two-byte even packed two digits appears X'012F' for positive twelve. Hex dump inspection confirms EVEN attribute applied correctly when copybook ambiguous.

Common Hex Mistakes

1. Odd digit count inside X literal—compile error.
2. Mask width shorter than field—high bits untouched unintentionally.
3. Expecting X'123' for packed 123—need sign nybble X'123F'.
4. Using ASCII hex constants on EBCDIC files without translation.
5. DISPLAY decimal on packed field instead of MASK HEX debug path.

Explain It Like I'm Five

Hex is a secret code for bytes. Instead of writing every bit as on-off, we use two symbols 0-9 and A-F for each chunk of eight switches. X'FF' means all eight switches in one chunk are on. Masks are stencils—you lay the stencil on your byte and paint only the spots that should change. That is how programs flip one flag without breaking the rest of the number.

Exercises

1. Write VALUE initializing two-byte flags to X'0000'.
2. Explain byte count in X'0123ABCD'.
3. Apply AND X'FF00' to two-byte field and describe cleared bits.
4. Contrast hex dump of N 123 vs P 123 vs literal X'F1F2F3'.
5. Add MASK HEX to packed field and describe DISPLAY output purpose.