diff --git a/worksheet1/asm_io.asm b/worksheet1/asm_io.asm
new file mode 100644
index 0000000000000000000000000000000000000000..2e6e666792b5fb894ac64e0c3128bb930694d77d
--- /dev/null
+++ b/worksheet1/asm_io.asm
@@ -0,0 +1,26 @@
+;
+; file: asm_io.asm
+; Assembly I/O routines
+; To assemble for DJGPP
+;   nasm -f coff -d COFF_TYPE asm_io.asm
+; To assemble for Borland C++ 5.x
+;   nasm -f obj -d OBJ_TYPE asm_io.asm
+; To assemble for Microsoft Visual Studio
+;   nasm -f win32 -d COFF_TYPE asm_io.asm
+; To assemble for Linux
+;   nasm -f elf -d ELF_TYPE asm_io.asm
+; To assemble for Watcom
+;   nasm -f obj -d OBJ_TYPE -d WATCOM asm_io.asm
+; IMPORTANT NOTES FOR WATCOM
+;   The Watcom compiler's C library does not use the
+;   standard C calling convention. For example, the
+;   putchar() function gets its argument from the
+;   the value of EAX, not the stack.
+
+
+%define NL 10
+%define CF_MASK 00000001h
+%define PF_MASK 00000004h
+%define AF_MASK 00000010h
+%define ZF_MASK 00000040h
+%define SF_MASK 00000080h
\ No newline at end of file