# Practical Examples: Pay to Public Key Hash (P2PKH)

Let's examine how constant and pushdata opcodes appear in Bitcoin's most common script type: **Pay to Public Key Hash (P2PKH)**. This will help you recognize these opcodes in real transactions.

#### Fully Assembled P2PKH Script

When a P2PKH transaction is validated, the script looks like this:

```
0x48 <signature> 0x20 <public_key> OP_CODESEPARATOR OP_DUP OP_HASH160 0x14 <public_key_hash> OP_EQUALVERIFY OP_CHECKSIG
```

**Note:** The **OP\_CODESEPARATOR** marks where scriptSig ends and scriptPubKey begins—the validation engine inserts it automatically.

#### Breaking Down the Pushdata Operations

Let's identify each pushdata operation:

**1. Pushing the signature (72 bytes):**

```
0x48 <signature>
```

* **0x48** = hexadecimal for 72
* Uses inline pushdata (72 is less than 75)
* Pushes a 72-byte ECDSA signature onto the stack

**2. Pushing the public key (32 bytes compressed):**

```
0x20 <public_key>
```

* **0x20** = hexadecimal for 32
* Uses inline pushdata (32 is less than 75)
* Pushes a 32-byte compressed public key onto the stack

**3. Pushing the expected public key hash (20 bytes):**

```
0x14 <public_key_hash> 
```

* **0x14** = hexadecimal for 20
* Uses inline pushdata (20 is less than 75)
* Pushes the 20-byte public key hash (the address hash) onto the stack

<figure><img src="/files/gfF3Onbnc6qwp1IZiXsj" alt=""><figcaption></figcaption></figure>

#### Typical Data Sizes in Bitcoin Script

Understanding common data sizes helps you recognize patterns:

| **Data Type**           | **Typical Size** | **Pushdata Method** |
| ----------------------- | ---------------- | ------------------- |
| Public key hash         | 20 bytes         | 0x14 (inline)       |
| SHA-256 hash            | 32 bytes         | 0x20 (inline)       |
| Compressed public key   | 33 bytes         | 0x21 (inline)       |
| Uncompressed public key | 65 bytes         | 0x41 (inline)       |
| ECDSA signature         | 70-73 bytes      | 0x46-0x49 (inline)  |
| Small data (metadata)   | <75 bytes        | Inline              |
| Medium data             | 76-255 bytes     | OP\_PUSHDATA1       |


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