;Problem 9.30
;
; Program asks user to enter their name, then greets the user:
; > Please enter your name: <user input>
; > Hello, <user input>
;
;
; R0: holds the input (from TRAP x20) & uses as output (for TRAP x21) and starting addresses for output strings
; R1: initializes to the starting of HELLO string & ends up pointing to the end of the string (need update after finish code)
; R2:
; R3:
; ...
.ORIG x3000
LEA R1,HELLO ; starting address of HELLO (going to find end of string for appending)
; get to end of HELLO string for writing/appending input
AGAIN LDR R2,R1,#0 ; load char at hello address into R2
BRz NEXT ; if done w/ string (x0000), go to NEXT
ADD R1,R1,#1 ; increment hello address
BR AGAIN
; print prompt for user input
NEXT LEA R0,PROMPT ; get address of prompt for user
TRAP x22 ; PUTS (output welcome message)
; fill in user input by appendding to where R1 points (after default HELLO string)
LD R3, NEGENTER ; store (through ld) NEGENTER into R3 for termination comparing later
AGAIN2 TRAP x20 ; GETC (gather user input one char at a time)
TRAP x21 ; OUT (output char for user on console)
ADD R2,R0,R3 ; check if user pressed ENTER key
BRz CONT ; if they did, we are done - go to CONT
STR R0,R1,#0 ; store value in R0 (user input) into memory (wherever end of HELLO string is pointing)
ADD R1,R1,#1 ; increment address of R1 so that we can write to the next available spot
BR AGAIN2
; print out Hello, <user name>
CONT AND R2,R2,#0 ; clear R2 (doesn't seem necessary - redundant? may be needed for bigger program where more things can get to CONT)
; ; may not need to do anything here (will discuss in class)
LEA R0, HELLO ; address of HELLO Prompt
TRAP x22 ; PUTS (output updated HELLO string)
TRAP x25 ; HALT (stop program)
NEGENTER .FILL xFFF6 ; -x0A
PROMPT .STRINGZ "Please enter your name: "
HELLO .STRINGZ "Hello, "
.BLKW #25
.END Write, Run & Share Assembly code online using OneCompiler's Assembly online compiler for free. It's one of the robust, feature-rich online compilers for Assembly language. Getting started with the OneCompiler's Assembly compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Assembly and start coding.
Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.
Every assembler may have it's own assembly language designed for a specific computers or an operating system.
Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.
Assembly language usually consists of three sections,
Data section
To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section
To declare variables
text section
_start specifies the starting of this section where the actually code is written.
There are various define directives to allocate space for variables for both initialized and uninitialized data.
variable-name define-directive initial-value
| Define Directive | Description | Allocated Space |
|---|---|---|
| DB | Define Byte | 1 byte |
| DW | Define Word | 2 bytes |
| DD | Define Doubleword | 4 bytes |
| DQ | Define Quadword | 8 bytes |
| DT | Define Ten Bytes | 10 bytes |
| Define Directive | Description |
|---|---|
| RESB | Reserve a Byte |
| RESW | Reserve a Word |
| RESD | Reserve a Doubleword |
| RESQ | Reserve a Quadword |
| REST | Reserve a Ten Bytes |
Constants can be defined using
CONSTANT_NAME EQU regular-exp or value
%assign constant_name value
%define constant_name value
Loops are used to iterate a set of statements for a specific number of times.
mov ECX,n
L1:
;<loop body>
loop L1
where n specifies the no of times loops should iterate.
Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.
procedure_name:
;procedure body
ret