| Register Number | Alternative Name | Description |
|---|---|---|
| 0 | $zero | Always the value 0. |
| 1 | $at | assembler temporary, reserved by the assembler. |
| 2 | $v0 | (values) from expression evaluation and function results. |
| 3 | $v1 | |
| 4 | $a0 | $a0 - $a3 (arguments) First four parameters for subroutine. Not preserved across procedure calls |
| 5 | $a1 | |
| 6 | $a2 | |
| 7 | $a3 | |
| 8 | $t0 | $t0 - $t7 (temporaries) Caller saved if needed. Subroutines can use w/out saving. Not preserved across procedure calls. |
| 9 | $t1 | |
| 10 | $t2 | |
| 11 | $t3 | |
| 12 | $t4 | |
| 13 | $t5 | |
| 14 | $t6 | |
| 15 | $t7 | |
| 16 | $s0 | $s0 - $s7 (saved values) - Callee saved. A subroutine using one of these must save original and restore it before exiting. Preserved across procedure calls. |
| 17 | $s1 | |
| 18 | $s2 | |
| 19 | $s3 | |
| 20 | $s4 | |
| 21 | $s5 | |
| 22 | $s6 | |
| 23 | $s7 | |
| 24 | $t8 | $t8 - $t9 (temporaries) Similar to $t0 - $t7 above. |
| 25 | $t9 | |
| 26 | $k0 | $k0 - $k1 reserved for use by the interrupt/trap handler. |
| 27 | $k1 | |
| 28 | $gp | global pointer. Points to middle of 64K block of memory in the static data segment. |
| 29 | $sp | stack pointer. Points to the top of the stack. |
| 30 | $fp or $s8 | saved value or frame pointer. Preserved across procedure calls. |
| 31 | $ra | return address |