Procedure - Computer Organization and Assembly Language - Lecture Slides, Slides of Assembly Language Programming

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Computer Organization &

Assembly Languages

Procedure

Chapter Overview

 Linking to an External Library

 The Book's Link Library

 Stack Operations

 Defining and Using Procedures

 Program Design Using Procedures

Link Library Overview

 A file containing procedures that have been

compiled into machine code

 constructed from one or more OBJ files

 To build a library,...

 start with one or more ASM source files

 assemble each into an OBJ file

 create an empty library file (extension .LIB)

 add the OBJ file(s) to the library file, using the

Microsoft LIB utility

Calling a Library Procedure

INCLUDE Irvine32.inc .code mov eax,1234h ; input argument call WriteHex ; show hex number call Crlf ; end of line

• Call a library procedure using the CALL instruction.

Some procedures require input arguments. The

INCLUDE directive copies in the procedure

prototypes (declarations).

• The following example displays "1234" on the console:

What's Next

 Linking to an External Library

 The Book's Link Library

 Stack Operations

 Defining and Using Procedures

 Program Design Using Procedures

Library Procedures - Overview

CloseFile – Closes an open disk file

Clrscr - Clears console, locates cursor at upper left corner

CreateOutputFile - Creates new disk file for writing in output mode

Crlf - Writes end of line sequence to standard output

Delay - Pauses program execution for n millisecond interval

DumpMem - Writes block of memory to standard output in hex

DumpRegs – Displays general-purpose registers and flags (hex)

GetCommandtail - Copies command-line args into array of bytes

GetMaxXY - Gets number of cols, rows in console window buffer

GetMseconds - Returns milliseconds elapsed since midnight

Library Procedures - Overview (cont.)

ReadFromFile – Reads input disk file into buffer

ReadDec - Reads 32-bit unsigned decimal integer from keyboard

ReadHex - Reads 32-bit hexadecimal integer from keyboard

ReadInt - Reads 32-bit signed decimal integer from keyboard

ReadKey – Reads character from keyboard input buffer

ReadString - Reads string from standard input, terminated by [Enter]

SetTextColor - Sets foreground and background colors of all

subsequent console text output

StrLength – Returns length of a string

WaitMsg - Displays message, waits for Enter key to be pressed

WriteBin - Writes unsigned 32-bit integer in ASCII binary format.

WriteBinB – Writes binary integer in byte, word, or doubleword format

WriteChar - Writes a single character to standard output

Library Procedures - Overview (cont.)

WriteDec - Writes unsigned 32-bit integer in decimal format

WriteHex - Writes an unsigned 32-bit integer in hexadecimal

format

WriteHexB – Writes byte, word, or doubleword in hexadecimal

format

WriteInt - Writes signed 32-bit integer in decimal format

WriteString - Writes null-terminated string to console window

WriteToFile - Writes buffer to output file

WriteWindowsMsg - Displays most recent error message

generated by MS-Windows

Example 2

.data str1 BYTE "Assembly language is easy!",

.code mov edx,OFFSET str call WriteString call Crlf

Display a null-terminated string and move the cursor

to the beginning of the next screen line.

Example 3

IntVal = 35 .code mov eax,IntVal call WriteBin ; display binary call Crlf call WriteDec ; display decimal call Crlf call WriteHex ; display hexadecimal call Crlf

Display an unsigned integer in binary, decimal, and

hexadecimal, each on a separate line.

Sample output:

Example 5

.code mov ecx,10 ; loop counter

L1: mov eax,100 ; ceiling value call RandomRange ; generate random int call WriteInt ; display signed int call Crlf ; goto next display line loop L1 ; repeat loop

Generate and display ten pseudorandom signed integers

in the range 0 – 99. Pass each integer to WriteInt in EAX

and display it on a separate line.

Example 6

.data str1 BYTE "Color output is easy!",

.code mov eax,yellow + (blue * 16) call SetTextColor mov edx,OFFSET str call WriteString call Crlf

Display a null-terminated string with yellow characters

on a blue background.

The background color is multiplied by 16 before being added to the foreground color.

Stack Operations

 Runtime Stack

 PUSH Operation

 POP Operation

 PUSH and POP Instructions

 Using PUSH and POP

 Example: Reversing a String

 Related Instructions

Runtime Stack

 Imagine a stack of plates...

 plates are only added to the top

 plates are only removed from the top

 LIFO (Last-In, First-Out) structure

 Push & pop operations

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