Machine Code - Example

Example

The MIPS architecture provides a specific example for a machine code whose instructions are always 32 bits long. The general type of instruction is given by the op (operation) field, the highest 6 bits. J-type (jump) and I-type (immediate) instructions are fully specified by op. R-type (register) instructions include an additional field funct to determine the exact operation. The fields used in these types are:

6 5 5 5 5 6 bits R-type I-type J-type

rs, rt, and rd indicate register operands; shamt gives a shift amount; and the address or immediate fields contain an operand directly.

For example adding the registers 1 and 2 and placing the result in register 6 is encoded:

0 1 2 6 0 32 decimal 000000 00001 00010 00110 00000 100000 binary

Load a value into register 8, taken from the memory cell 68 cells after the location listed in register 3:

35 3 8 68 decimal 100011 00011 01000 00000 00001 000100 binary

Jumping to the address 1024:

2 1024 decimal 000010 00000 00000 00000 10000 000000 binary