Data Types in Assembly: BYTE, WORD and DWORD

Statement Purpose:

In this lab, student will know about the almost each and every data types assembly language support and their compatibility with high level programming languages.

Prior to the arrival of MASM, most assemblers provided very little capability for declaring and allocated complex data types. Generally, you could allocate bytes, words, and other primitive machine structures. You could also set aside a block of bytes. As high level languages improved their ability to declare and use abstract data types, assembly language fell farther and farther behind. Then MASM came along and changed all that. Unfortunately, many long time assembly language programmers haven’t bothered to learn the new MASM syntax for things like arrays, structures, and other data types. Likewise, many new assembly language programmers don’t bother learning and using these data typing facilities because they’re already overwhelmed by assembly language and want to minimize the number of things they’ve got to learn. This is really a shame because MASM data typing is one of the biggest improvements to assembly language since using mnemonics rather than binary opcodes for machine level programming.

Activity Outcomes:

This lab teaches you the following topics:

• Understand data types in Assembly
• Storage considerations for each type
• Declaration of Integers, real, characters, strings, and arrays
• Various operators
• Data movement instructions

Instructor Note:

As pre-lab activity, read Chapter 3 from the book (Assembly Language for X86 processors, KIP

1. IRVINE., 7th Edition (2015), Pearson), and also as given by your theory instructor.

Introduction

MASM defines intrinsic data types, each of which describes a set of values that can be assigned to variables and expressions of the given type. The essential characteristic of each type is its size in bits: 8, 16, 32, 48, 64, and 80. Other characteristics (such as signed, pointer, or floating-point) are optional and are mainly for the benefit of programmers who want to be reminded about the type of data held in the variable. A variable declared as DWORD, for example, logically holds an unsigned 32-bit integer. In fact, it could hold a signed 32-bit integer, a 32-bit single precision real, or a 32-bit pointer. The assembler is not case sensitive, so a directive such as DWORD can be written as dword, Dword, dWord, and so on.

Lab Activities:

Activity 1:

Write a program that contains a definition of each data type listed in Table given below. Initialize each variable to a value that is consistent with its data type.

 

Type	Usage
BYTE	8-bit unsigned integer. B stands for byte
SBYTE	8-bit signed integer. S stands for signed
WORD	16-bit unsigned integer
SWORD	16-bit signed integer
DWORD	32-bit unsigned integer -D stands for double
SDWORD	32-bit signed integer. SD stands for signed
QWORD	64-bit integer. Q stands for quad
TBYTE	80-bit (10-byte) integer. T stands for Ten-byte
REAL4	32-bit (4-byte) IEEE short real
REAL8	64-bit (8-byte) IEEE long real
REAL10	80-bit (10-byte) IEEE extended real

 

Solution:

INCLUDE Irvine32.inc

.data

var1 BYTE 10h var2 SBYTE -14

var3 WORD 2000h var4 SWORD +2345

var5 DWORD 12345678h var6 SDWORD -2342423

var7 FWORD 0

var8 QWORD 1234567812345678h var9 TBYTE 1000000000123456789Ah var10 REAL4 -1.25

var11 REAL8 3.2E+100

var12 REAL10 -6.223424E-2343

.code

main PROC

exit main ENDP END main

Activity 2:

Write a program that defines symbolic constants for all of the days of the week. Create an array variable that uses the symbols as initializes.

Solution:

INCLUDE Irvine32.inc

Sunday    = 0

Monday    = 1

Tuesday = 2

Wednesday = 3

Thursday = 4

Friday    = 5

Saturday = 6

.data

myDays BYTE Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday

.code

main PROC

exit main ENDP END main

Activity 3:

Write a program that defines symbolic names for several string literals (characters between quotes). Use each symbolic name in a variable definition.

Solution:

 INCLUDE Irvine32.inc

sym1 TEXTEQU <“System failure”>

sym2 TEXTEQU <“Press any key to continue…”> sym3 TEXTEQU <“Insufficient user training”> sym4 TEXTEQU <“Please re-start the system”>

.data

msg1 BYTE sym1 msg2 BYTE sym2 msg3 BYTE sym3 msg4 BYTE                              sym4

.code

main PROC

exit main ENDP END main

Home Activities:

Home Task 1:

Define the following data in Assembly

 

Sort           BYTE              ’y’                    ; ASCII of y = 79H

value          WORD                         25159                         ; 25159D = 6247H total                        DWORD          542803535 ;   542803535D = 205A864FH

marks	DWORD	0, 0, 0, 0, 0, 0, 0, 0
value1	BYTE ‘A’	; character constant
value2	BYTE 0	; smallest unsigned byte
value3	BYTE 255	; largest unsigned byte
value4	SBYTE -128	; smallest signed byte
value5	SBYTE +127	; largest signed byte
value6	BYTE ?	; uninitialized byte

 

Home Task 2:

Create the following menu by declaring a string in Assembly Language.

 Checking Account

• Create a new account.
• Open an existing account
• Credit the account
• Debit the account
• Exit

 

Home Task 3:

Create the following arrays in Assembly Language.

 

• Array of ten
• Array of 100
• Arrays of 4×3 integers
• Array of 4x3x2

Home Task 4:

Implement each of the following declarations in assembly language:

• char initial;
• char grade = ‘B’;
• char x = ‘P’, y = ‘Q’;
• int amount;
• int count = 0;
• int number = -396;