|-
| PC (Program Counter) || 16-bit || Points to the next instruction || Automatically increments as instructions execute
|}
== GBZ80 instructions ==
=== 8-bit ALU group ===
{| class="wikitable" style="white-space: nowrap;"
|-
! Instruction !! Opcode !! Cycles !! Z !! N !! H !! C !! Effect !! Description
|-
| inc r || 00rrr100 || 1 || rowspan=2|+ || rowspan=2|0 || rowspan=2|+ || rowspan=2|- || r += 1 ||rowspan=2|Increment
|-
| inc (hl) || 00110100 || 3 || (hl) += 1
|-
| dec r || 00rrr101 || 1 || rowspan=2|+ || rowspan=2|1 || rowspan=2|+ || rowspan=2|- || r -= 1 ||rowspan=2|Decrement
|-
| dec (hl) || 00110101 || 3 || (hl) -= 1
|-
| add a,r || 10000rrr || 1 || rowspan=3|+ || rowspan=3|0 || rowspan=3|+ || rowspan=3|+ || a += r ||rowspan=3|Add
|-
| add a,(hl) || 10000110 || 2 || a += (hl)
|-
| add a,n || 11000110 nnnnnnnn || 2 || a += n
|-
| adc a,r || 10001rrr || 1 || rowspan=3|+ || rowspan=3|0 || rowspan=3|+ || rowspan=3|+ || a += r + cf ||rowspan=3|Add with Carry
|-
| adc a,(hl) || 10001110 || 2 || a += (hl) + cf
|-
| adc a,n || 11001110 nnnnnnnn || 2 || a += n + cf
|-
| sub r || 10010rrr || 1 || rowspan=3|+ || rowspan=3|1 || rowspan=3|+ || rowspan=3|+ || a -= r ||rowspan=3|Subtract
|-
| sub (hl) || 10010110 || 2 || a -= (hl)
|-
| sub n || 11010110 nnnnnnnn || 2 || a -= n
|-
| sbc a,r || 10011rrr || 1 || rowspan=3|+ || rowspan=3|1 || rowspan=3|+ || rowspan=3|+ || a -= r + cf ||rowspan=3|Subtract with Carry
|-
| sbc a,(hl) || 10011110 || 2 || a -= (hl) + cf
|-
| sbc a,n || 11011110 nnnnnnnn || 2 || a -= n + cf
|-
| and r || 10100rrr || 1 || rowspan=3|+ || rowspan=3|0 || rowspan=3|1 || rowspan=3|0 || a := a and r ||rowspan=3|Logical AND
|-
| and (hl) || 10100110 || 2 || a := a and (hl)
|-
| and n || 11100110 nnnnnnnn || 2 || a := a and n
|-
| xor r || 10101rrr || 1 || rowspan=3|+ || rowspan=3|0 || rowspan=3|0 || rowspan=3|0 || a := a xor r ||rowspan=3|Logical eXclusive OR
|-
| xor (hl) || 10101110 || 2 || a := a xor (hl)
|-
| xor n || 11101110 nnnnnnnn || 2 || a := a xor n
|-
| or r || 10110rrr || 1 || rowspan=3|+ || rowspan=3|0 || rowspan=3|0 || rowspan=3|0 || a := a or r ||rowspan=3|Logical Inclusive OR
|-
| or (hl) || 10110110 || 2 || a := a or (hl)
|-
| or n || 11110110 nnnnnnnn || 2 || a := a or n
|-
| cp r || 10111rrr || 1 || rowspan=3|+ || rowspan=3|1 || rowspan=3|+ || rowspan=3|+ || tmp := a - r ||rowspan=3|Compare
|-
| cp (hl) || 10111110 || 2 || tmp := a - (hl)
|-
| cp n || 11111110 nnnnnnnn || 2 || tmp := a - n
|}