September 2017 Update

Task/Factorial/X86-Assembly/factorial-1.x86

@@ -0,0 +1,11 @@
+global factorial
+section .text
+
+; Input in ECX register (greater than 0!)
+; Output in EAX register
+factorial:
+  mov   eax, 1
+.factor:
+  mul   ecx
+  loop  .factor
+  ret

Task/Factorial/X86-Assembly/factorial-2.x86

@@ -0,0 +1,20 @@
+global fact
+section .text
+
+; Input and output in EAX register
+fact:
+  cmp    eax, 1
+  je    .done   ; if eax == 1 goto done
+
+  ; inductive case
+  push  eax  ; save n (ie. what EAX is)
+  dec   eax  ; n - 1
+  call  fact ; fact(n - 1)
+  pop   ebx  ; fetch old n
+  mul   ebx  ; multiplies EAX with EBX, ie. n * fac(n - 1)
+  ret
+
+.done:
+  ; base case: return 1
+  mov   eax, 1
+  ret

Task/Factorial/X86-Assembly/factorial-3.x86

@@ -0,0 +1,17 @@
+global factorial
+section .text
+
+; Input in ECX register
+; Output in EAX register
+factorial:
+  mov   eax, 1  ; default argument, store 1 in accumulator
+
+.base_case:
+  test  ecx, ecx
+  jnz   .inductive_case  ; return accumulator if n == 0
+  ret
+
+.inductive_case:
+  mul   ecx         ; accumulator *= n
+  dec   ecx         ; n -= 1
+  jmp   .base_case  ; tail call