What is the machine code of the mnemonic code “LDR r6, [r5, #4]”

The machine code of the mnemonic code "LDR r6, [r5, #4]" depends on the specific architecture and instruction set being used.

For example, on ARMv7 architecture, the machine code for this instruction would be:

0x58 0x5e 0x08 0x04

Where:
- `0x58` is the opcode for the LDR instruction with the addressing mode as [register + immediate offset]
- `0x5e` is the encoded value of the destination register r6
- `0x08` is the encoded value of the base register r5
- `0x04` is the 12-bit immediate offset value (4 in decimal) which is added to the base register to form the memory address for data transfer.

It's worth noting that the machine code representation of instructions can vary depending on the specific processor architecture and instruction set being used.