lesson 5 with hex printer

05-bootsector-functions-strings/README.md

@@ -110,15 +110,26 @@ The syntax is
 %include "file.asm"
 ```
 
+
+Printing hex values
+-------------------
+
+In the next lesson we will start reading from disk, so we need some way
+to make sure that we are reading the correct data. File `boot_sect_print_hex.asm`
+extends `boot_sect_print.asm` to print hex bytes, not just ASCII chars.
+
+
 Code! 
 -----
 
 Let's jump to the code. File `boot_sect_print.asm` is the subroutine which will
 get `%include`d in the main file. It uses a loop to print bytes on screen.
-
-The main file `boot_sect_main.asm` loads a couple strings, calls `print` and hangs. If you understood
-the previous sections, it's quite straightforward.
-
-As a last goodie, we will learn how to print newlines. The familiar `'\n'` is
+It also includes a function to print a newline. The familiar `'\n'` is
 actually two bytes, the newline char `0x0A` and a carriage return `0x0D`. Please
 experiment by removing the carriage return char and see its effect.
+
+As stated above, `boot_sect_print_hex.asm` allows for printing of bytes.
+
+The main file `boot_sect_main.asm` loads a couple strings and bytes,
+calls `print` and `print_hex` and hangs. If you understood
+the previous sections, it's quite straightforward.

05-bootsector-functions-strings/boot_sect_main.asm

@@ -4,22 +4,23 @@
 mov bx, HELLO
 call print
 
-; We will get fancy and print a newline
-; feel free to integrate newline code into "boot_sect_print"
-mov ah, 0x0e
-mov al, 0x0A ; newline char
-int 0x10
-mov al, 0x0D ; carriage return char
-int 0x10
+call print_nl
 
 mov bx, GOODBYE
 call print
 
+call print_nl
+
+mov dx, 0x1234
+call print_hex
+
 ; that's it! we can hang now
 jmp $
 
 ; remember to include subroutines below the hang
 %include "boot_sect_print.asm"
+%include "boot_sect_print_hex.asm"
+
 
 ; data
 HELLO:

05-bootsector-functions-strings/boot_sect_print.asm

@@ -21,3 +21,17 @@ start:
 done:
     popa
     ret
+
+
+
+print_nl:
+    pusha
+    
+    mov ah, 0x0e
+    mov al, 0x0a ; newline char
+    int 0x10
+    mov al, 0x0d ; carriage return
+    int 0x10
+    
+    popa
+    ret