# !a (assemble physical address)

### Command

> !a

### Syntax

> !a \[Address (hex)] \[asm {AsmCmd1; AsmCmd2}]

### Description

Assembles (shows HEX byte codes) or puts the resulting instruction codes into the (physical) memory.

### Parameters

**\[Address (hex)] (optional)**

The **physical** address of where we want to start putting resulting codes into its memory.

{% hint style="info" %}
If the **Address** is empty, you can use it to only assemble instructions without modifying the memory.
{% endhint %}

**\[asm {AsmCmd1; AsmCmd2}]**

The target assembly codes.

{% hint style="danger" %}
Process ID doesn't make sense in physical memory. If you specify **pid** for physical memory, it is ignored.
{% endhint %}

### Examples

If you just want to view the result of assembly (byte codes in HEX) without modifying the memory, the following command can be used.

```
HyperDbg> !a { nop; xor rax, rax; nop }
warning, no start address provided to calculate relative asm commands

generated assembly: 5 bytes, 3 statements ==>>  nop; xor rax, rax; nop  = 90 48 31 c0 90
```

The following command is used when we want to assemble assembly codes and put the resulting bytes into the target memory at `abc1c0` .

```diff
HyperDbg> !a abc1c0 { nop; nop; nop }
generated assembly: 3 bytes, 3 statements ==>>  nop; nop; nop  = 90 90 90
successfully assembled at 0xabc1c0 address
```

### IOCTL

None

### Remarks

* By default, HyperDbg converts addresses to the object names (if the symbol for that address is available). If you want to see the address in hex format, you can turn `addressconversion` to **off** using the '[settings](https://docs.hyperdbg.org/commands/debugging-commands/settings)' command.
* To view the byte code of an assembly snippet, you can use the following command (`StartAddress` is useful when dealing with relative instructions like **JMP**).

```
 !a {jmp <nt!ExAllocatePoolWithTag+10>} [StartAddress]
```

{% hint style="success" %}
HyperDbg uses [**keystone**](https://github.com/keystone-engine/keystone) as its core assembler.
{% endhint %}

This command is guaranteed to keep debuggee in a halt state (in Debugger Mode); thus, nothing will change during its execution.

### Requirements

None

### Related

[Keystone](https://www.keystone-engine.org/)

[a (assemble virtual address)](https://docs.hyperdbg.org/commands/debugging-commands/a)

[u, u64, u2, u32 (disassemble virtual address)](https://docs.hyperdbg.org/commands/debugging-commands/u)

[!u, !u64, !u2, !u32 (disassemble physical address)](https://docs.hyperdbg.org/commands/extension-commands/u)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.hyperdbg.org/commands/extension-commands/a.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.