R-type

Assembly Language

Format: [instruct] [rd] [rs1] [rs2]

• [instruct] name of the instructions
• [rd] destination register
• [rs1], [rs2] source registers
• e.g., add $t0 $t1 $t2 : add $t1, $t2 → store in $t0

Machine Language

• op (operation code):
  • indicate the type of an instruction;
  • e.g., R-type instructions have opcode 000000
• rs, rt, rd:
  • Indicate which registers;
  • Use 5-bits because we have 32 general-purpose registers.
• shamt: used in shift instruction; how many positions (bits) to shift
• funct: indicate which instruction; e.g., 100000 -> add