Opcode Explained

Appearance

OP_GREATERTHAN ​

INFO

Opcode number: 160
Byte representation: 0xa0
Short description: Pop the top two items; push 1 if the second is greater than the top, 0 otherwise.

OP_GREATERTHAN compares the top two items on the stack as integers. If the second item is greater than the top item, it pushes 1 (true) onto the stack. If not, it pushes an empty array (false). Both items are removed from the stack after the comparison.

Operation ​

  1. Take the top item (a) and the second item (b) from the stack.
  2. Compare the two items:
    • If b > a, push 1 (true) onto the stack.
    • Otherwise, push an empty array (false) onto the stack.
  3. Remove the original items from the stack.

Notes ​

  • Both items must be valid integers. Bitcoin Script interprets byte arrays up to 4 bytes as integers.
  • An empty array ([]) is treated as 0 when compared.
  • If there are fewer than two items on the stack when OP_GREATERTHAN is executed, the script will fail.

Examples ​

Example 1: Second item is greater than the top item ​

shell
# ASM script
OP_3 OP_2 OP_GREATERTHAN

# Raw script
5352a0

# Stack (before OP_GREATERTHAN)
2  # top
3

# Stack (after OP_GREATERTHAN)
1  # true, as 3 > 2

Example 2: Comparing two zeros ​

shell
# ASM script
OP_PUSHBYTES_1 00 OP_0 OP_GREATERTHAN

# Raw script
0100009f

# Stack (before OP_GREATERTHAN)
[] # top (zero)
0  # second (zero)

# Stack (after OP_GREATERTHAN)
[]  # false