From 3d82656426a57e002905042ebbe94126a78ccfc8 Mon Sep 17 00:00:00 2001
From: SowinskiBraeden <braeden@sowinski.dev>
Date: Fri, 14 Nov 2025 13:45:43 -0800
Subject: [PATCH] factorial

---
 .gitignore  |   1 +
 Dockerfile  |  11 --------
 Makefile    |  21 +++++++++++++++
 README.md   |  12 ---------
 factorial   | Bin 0 -> 13536 bytes
 factorial.c |  22 ++++++++++++++++
 factorial.s |  72 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.asm    |   0
 8 files changed, 116 insertions(+), 23 deletions(-)
 create mode 100644 .gitignore
 delete mode 100644 Dockerfile
 create mode 100644 Makefile
 create mode 100755 factorial
 create mode 100644 factorial.c
 create mode 100644 factorial.s
 delete mode 100644 main.asm

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5761abc
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*.o
diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index bb720ef..0000000
--- a/Dockerfile
+++ /dev/null
@@ -1,11 +0,0 @@
-FROM ubuntu:latest
-
-RUN apt-get update && apt-get install -y nasm gcc gdb vim
-
-COPY main.asm /app/main.asm
-
-WORKDIR /app
-RUN nasm -f elf64 main.asm -o main.o
-RUN ld main.o -o main
-
-CMD ["./main"]
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..f6cffca
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,21 @@
+ASM      = as  # GNU Assembler
+LD       = gcc # GCC Linker
+LD_FLAGS = -nostartfiles
+
+SRC = factorial.s
+OBJ = factorial.o
+OUT = factorial
+
+all: $(OUT)
+
+$(OBJ): $(SRC)
+	$(ASM) $(SRC) -o $(OBJ)
+
+$(OUT): $(OBJ)
+	$(LD) $(LD_FLAGS) $(OBJ) -o $(OUT)
+
+run: all
+	./$(OUT)
+
+clean:
+	rm -f $(OBJ) $(OUT)
diff --git a/README.md b/README.md
index db018aa..756cee7 100644
--- a/README.md
+++ b/README.md
@@ -1,15 +1,3 @@
 # Assembly Project Demonstration - Factorial with Recursion
 Demonstrate how functoin calls work in assembly by using
 a factorial recursion example.
-
-## Build
-
-```bash
-docker build -t asm .
-```
-
-## Run
-
-```bash
-docker run asm
-```
diff --git a/factorial b/factorial
new file mode 100755
index 0000000000000000000000000000000000000000..384a46d31fd1f917bf071b7156894ebda93519ba
GIT binary patch
literal 13536
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zqW(ZH)juc|_8}<fsi)W%!_XcgtRQGQXXc#EM)#qpp3Z@}-#y<w=iWQt&RrPh-rIv0
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zH(F~5>Hy(BLWUz$;eFiS{BS(TXNp7rE8_g)>Z2bWbXP#YUGqMA3fNEl!3f_*d|QO?
zAig8QBfZtQDd1xu3GYh}(xDiDD*-#^`Md)2CjuTM>}Dp!^L6;)I=q@N$Gw8<m^rQR
zv#v5`(Kg1RP*x#tt7+HCdxmS44a=EyJY@`A89I6K+-YSPnPSl>dZr7cZJC}4khhf5
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wt*azW82|S$m-AV_7T|d7AdiY9ohKUGNJ5>utFe2awpIQO%6Dp!VI`XX16UH#5C8xG

literal 0
HcmV?d00001

diff --git a/factorial.c b/factorial.c
new file mode 100644
index 0000000..013b30d
--- /dev/null
+++ b/factorial.c
@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int factorial(int n)
+{
+    if (n <= 1)
+    {
+        return n;
+    }
+
+    return n * factorial(n - 1);
+}
+
+int main(void)
+{
+    int f;
+
+    f = factorial(5);
+
+    printf("%d\n", f);
+
+    return 0;
+}
diff --git a/factorial.s b/factorial.s
new file mode 100644
index 0000000..0979c06
--- /dev/null
+++ b/factorial.s
@@ -0,0 +1,72 @@
+.intel_syntax noprefix # allow mov rax, 1 syntax in GAS (GNU Assembly)
+.global _start
+
+# factorial
+# - rdi as input number
+# - rax as result
+factorial:
+    push rbp
+    mov rbp, rsp
+
+    cmp rdi, 1
+    jle base_case      # if n <= 1 return 1
+
+    push rdi           # save n
+    dec rdi            # rdi = n-1
+    call factorial     # rax = factorial(n-1)
+
+    pop rdx            # rdx = original n
+    imul rax, rdx      # rax = factorial(n-1) * n
+    jmp done
+
+base_case:
+    mov rax, 1
+
+done:
+    mov rsp, rbp
+    pop rbp
+    ret
+
+print_rax_digit:
+    sub rsp, 16
+
+    mov rbx, 10
+
+    # ones digit
+    xor rdx, rdx
+    mov rcx, rax
+    div rbx
+    add dl, '0'
+    mov [rsp+2], dl
+
+    # tens digit
+    xor rdx, rdx
+    mov rcx, rax
+    div rbx
+    add dl, '0'
+    mov [rsp+1], dl
+
+    # hundreds digit
+    add al, '0'
+    mov [rsp], al
+
+    mov rax, 1
+    mov rdi, 1
+    mov rsi, rsp
+    mov rdx, 3
+    syscall
+
+    add rsp, 16
+    ret
+
+_start:
+    mov rdi, 5 # Use 5 for our example input
+    mov rax, 1 # Set starting result to 1
+
+    call factorial
+
+    call print_rax_digit
+
+    mov rax, 60 # syscall exit - 64 bit
+    mov rdi, 0  # exit code
+    syscall
diff --git a/main.asm b/main.asm
deleted file mode 100644
index e69de29..0000000