added fizzbuzz program

section_1/fizzbuzz/fizzbuzz.s

@@ -0,0 +1,91 @@
+/*		Perry Kivolowitz
+		CSC3510
+*/
+		.global	main
+		.text
+		.align	2
+
+/*	FizzBuzz - a classic interview question.
+
+	Count from 0 to n (let's make it 100).
+	If the value is divisible by 3, print Fizz
+	If the value is divisible by 5, print Buzz
+	If the value is divisible by both 3 and 5, print FizzBuzz
+	Otherwise, print the number.
+*/
+
+/*	Bible:
+
+	x20		counter
+	w21		bool that says whether or not I have printed anything
+*/
+
+/*	mod(a, b) - implements a % b
+	integer divide a by b - for example - 5 % 3 would need 5 // 3 yielding 1
+	multiply result by b - 1 * 3 is 3
+	subtract result from a - 5 - 3 yielding 2 and that's our return value.
+*/
+mod:	sdiv 	x2, x0, x1				// x2 gets a // b
+		msub	x0, x2, x1, x0			// x0 gets a - a // b * b 	
+		ret
+
+main:	stp		x20, x30, [sp, -16]!
+		str		x21, [sp, -16]!
+
+		mov		x20, xzr
+1:		cmp		x20, 100
+		bge		99f
+
+		mov		w21, wzr
+
+		// Test for divisible by 3
+		mov		x0, x20
+		mov		x1, 3
+		bl		mod
+		cbnz	x0, 5f
+		// If we get here, the counter was divisible by 3
+		ldr		x0, =fizz
+		bl		printf
+		add		w21, w21, 1
+
+5:		mov		x0, x20
+		mov		x1, 5
+		bl		mod
+		cbnz	x0, 10f
+		// If we get here, the counter was divisible by 5
+		ldr		x0, =buzz
+		bl		printf
+		add		w21, w21, 1
+
+10:		cbz 	w21, 20f
+		// If we get here, it means that we have printed
+		// something (either fizz, or buzz or fizzbuzz)
+		// so all we need now is a new line
+		ldr		x0, =nl
+		bl		puts
+		b 		80f
+
+20:		// If we get here, the counter was neither a
+		// multiple of 3 nor of 5. Therefore, we need
+		// to print the counter itself.
+
+ 		ldr		x0, =fmt
+		mov		x1, x20
+		bl 		printf
+
+80:		add		x20, x20, 1
+		b 		1b		
+
+
+99:		ldr		x21, [sp], 16
+		ldp		x20, x30, [sp], 16
+		mov		w0, wzr
+		ret
+
+		.data
+fizz:	.asciz	"Fizz"
+buzz:	.asciz	"Buzz"
+nl:		.asciz	""
+fmt:	.asciz	"%ld\n"
+
+		.end