Opcode Explained

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OP_1ADD ​

INFO

Opcode number: 139
Byte representation: 0x8b
Short description: Add 1 to the top item on the stack.

OP_1ADD increments the top item on the stack by 1. This operation is used in Bitcoin Script when simple arithmetic is needed, often for counting or adjusting values during script execution.

Operation ​

  1. Take the top item from the stack.
  2. Add 1 to this item.
  3. Push the result back onto the stack as the new top item.

Notes ​

  • Arithmetic inputs are limited to signed 32-bit integers, but may overflow their output.
  • If the input value for OP_1ADD is longer than 4 bytes, the script will fail.
  • If the stack is empty when OP_1ADD is executed, the script will fail.

Example ​

Incrementing a stack item:

shell
# ASM script
OP_2 OP_1ADD

# Raw script
528b

# Stack (before OP_1ADD)
2

# Stack (after OP_1ADD)
3 # result after adding 1