adds user input program

src/1_8.asm

@@ -1,21 +1,16 @@
-; assembly that shows how to return values to a
-; a C function
-
     option casemap:none
 
 ; constants
-nl      =       10
-maxlen  =       256
+nl      =   10   ; newline
+maxlen  =   256 ; max len of the string
 
     .data
 
-title_str   byte        "Listing 1-8", 0
-prompt      byte        "Enter a string: ", 0
-fmt_string  byte        "User entered: '%s'", nl, 0
-
-; make `maxlen` copies/duplicates of size byte, each uinitialized
-input       byte maxlen dup (?)
+title_string    byte    'Listing 1_8', 0
+prompt_string   byte    'Enter a string: ', 0
+format_string   byte    'User entered: "%s" ', nl, 0
 
+input   byte    maxlen dup (?) ; make maxlen copies of byte, each uninitialized
 
     .code
 
@@ -23,39 +18,37 @@ input       byte maxlen dup (?)
     externdef readline:proc
 
     public get_title
-
-; procedure loads the address of the title_str into the RAX
-; register, this is the register where C expects to find 
-; the return of this proc. (WINDOWS ABI)
 get_title proc
     
-    lea rax, title_str  ; load address of title string in RAX register
-    ret
+    lea rax, title_string
+    ret 
 
 get_title endp
 
-; ASM Main function
     public asm_main
-asm_main proc 
+asm_main proc
 
-    sub     rsp, 56
-    
-    lea     rcx, prompt     ; load prompt string address into RCX register
-    call    printf          ; this is the reigster where ABI tells us to place arguments
+    sub rsp, 56
 
-    mov     input, 0        ; ensure the input string is terminated with 0
+    ; first we want to print a prompt, to do this we use the C++ function printf
+    ; we load this prompt in RCX and then call
+    lea rcx, prompt_string
+    call printf
 
-    lea     rcx, input      ; load input address to rcx register
-    mov     rdx, maxlen     ; move maxlen into rdx register
-    call    readline        ; use rcx and rdx as arguments to call readline
+    mov input, 0
 
-    lea     rcx, fmt_string
-    lea     rdx, input
-    call    printf
+    ; read user input
+    lea rcx, input
+    mov rdx, maxlen
+    call readline
 
-    add     rsp, 56
+    lea rcx, format_string
+    lea rdx, input
+    call printf
+
+    add rsp, 56
     ret
 
 asm_main endp
 
-    end
+    end

src/build.bat

@@ -6,4 +6,4 @@ REM /c is compile dont link
 REM /Zi is debug info
 REM /Cp is preserve cases
 ml64 /nologo /c /Zi /Cp %1.asm
-cl /nologo /O2 /Zi /utf-8 /EHa /Fe%1.exe main.cpp %1.obj
+cl /nologo /O2 /Zi /utf-8 /EHa /Fe%1.exe c.cpp %1.obj

src/c.cpp

@@ -8,7 +8,6 @@ extern "C"
 {
     void asm_main(void);
 
-
     char *get_title(void);
 
     int readline(char* dest, int maxlen);