What is meaning of .model small in 8086 programs?

assembly masm x86-16
Sakil Mallick picture Sakil Mallick · Nov 12, 2017 · Viewed 17k times · Source

I am a beginner in 8086 assembly language. I can understand the logic used in the program and write small programs myself. But I just want to know what this does:

.model small
.stack 300h

What is explanation for .model small?

I am using masm.

Answer

Sep Roland picture Sep Roland · Nov 12, 2017

With .model tiny you get a program where CS, DS, and SS are all pointing to the same 64KB of memory. The stack is placed in the highest region of this 64KB segment.

With .model small you get a program where CS points to a segment of its own, followed by the segment where DS and SS are pointing to. The stack is placed in the highest region of the SS segment.

The directive .stack 300h is telling MASM the size of the stack, so MASM can warn you when the rest of the program (data,bss,heap) would clash with the stack.

In both these models all access to data items is done using near pointers.

Related questions

What does OFFSET in 16 bit assembly code mean?

I am going through some example assembly code for 16-bit real mode. I've come across the lines: mov bx, cs mov ds, bx mov si, OFFSET value1 pop es mov di, OFFSET value2 what is this doing? What does having …

Read More
8086 masm program for palindrome checking

.code > > start: > mov ax,03h > int 10h > mov ax,seg msg1 > mov ds,ax > mov dx,offset msg1 > mov ah,09h > int 21h > mov si,offset str > read: > …

Read More
How to prompt user for string and display it again in Assembly Language Programming

I'm having trouble with my assembly language code. We were asked to prompt user for input string and we're supposed to display it again or echo it to the command line. We need to assume that it's only up to 20 …

Read More