Purpose Load a with 69 and compare it to 68 (cp 68), display Z if the zero flag was set or N if it was reset. Assume this is a call and that the cursor coordinates are already set up.
Code
	ld a,69		;number to check
	cp 68		;number to compare it to
	jr z,zero	;if zero branch to 'zero'
	jr nz,not_zero	;it n-zero branch to 'not_zero'
zero:
	ld a,'Z'	;load a with letter
	jr display_it
not_zero:
	ld a,'N'	;load a with letter
display_it:
	jp _putc	;display whatever's in a...ret
	
Error Remember that the flags are stored as bits in the f register. Bits have two possible states: set or reset. This means that the condition could only have resulted in zero or not zero. If we test for only one of those conditions we will know what the zero flag's status is. It's kinda like getting the wrong answer on a true/false test...if you put 'true' and got it wrong, then you know the answer's 'false'! Using this we can rearrange the order of the components of that routine and only have to test one condition. If that condition is false, then don't branch (another name for jump) and lead into the next segment of code. We were good to use a lead in after the 'not_zero' component.
Fixed Code
	ld a,69		;number to check
	cp 68		;number to compare it to
	ld a,'Z'	;load a with character
	jr z,zero	;was it zero...branch
	ld a,'N'	;load a with character
display_it:		;lead into 'display_it'
	jp _putc	;display whatever's in a...ret