#######################################################################

# Lab #4

# Name:

# Date:

#

#

# Description:

#

# The purpose of this lab is to help you understand dynamic arrays,

# how to access a specific element in an array through its index,

# and how to iterate or search in an array.

#

# - In first part of your program, you should ask user input

# an array length (greater than 0), then use allocalte_array

# subprogram to dynamically allocate an array in heap, and

# store base address and length to static variables. After

# that, use the provided subprogram to read input from user

# and print out the array.

#

# - In second part of your program, main should use a loop

# repeatedly ask user to input a number, call subprogram

# array_contains to see whether the array contains this

# number, and print out the index of the number after

# return. The loop should end if user input -1. array_contains

# will take 3 arguments IN (array base address, array

# length, and user input number) and 1 argument OUT (index

# of the number if array contains the number, -1 if not).

#

# - In third part of your program, main should use another

# loop ask user to input an index (0 <= index < 10), and

# call print_nth to locate and print the element at that

# index. Again, loop should end if user input -1. You

# should print an error message if user input an invalid

# index. print_nth will take 2 arguments IN (array base

# address, and user input index) and no argument out.

#

# (Hint) check exit code before validate user input since

# -1 is also an invalid input.

#

# - Please notice that all register usage are recomandations

# not requirements, feel free to follow your own design.

#

#######################################################################

# Register Usage

#

# $t0

# $t1

# $t2

# $t3

# $t4

# $t5

# $t6

# $t7 temp register

# $t8 holds 10

# $t9 holds -1

#######################################################################

.data

array_prompt_p: .asciiz " Please enter array length (0 < n <=10): "

array_error_p: .asciiz "Invalid length, should be positive and no more than 10. "

number_prompt_p: .asciiz " Please enter a number to search (-1 to stop): "

not_exist_p: .asciiz "Array does not contain the number. "

exist_p: .asciiz "The index of the number is: "

index_prompt_p: .asciiz " Please enter an index less than array length (-1 to stop): "

index_error_p: .asciiz "Wrong index (0 <= index < array length). "

array_dynamic: .word 0

array_length: .word 0

#######################################################################

.text

main:

li $t9, -1 # load -1 to $t9 as condition

li $t8, 10

create_array:

li $v0, 4 # prompt user for array length

la $a0, array_prompt_p

syscall

li $v0, 5 # user input

syscall

blez $v0, invalid_length # go to invalid if input <= z

bgt $v0, $t8, invalid_length # go to invalid if input > 10

la $t7, array_length # store valid array length

sw $v0, 0($t7) # to static variable

# TODO: put array length in $a0

move $a0, $v0

# TODO: call subprogram allocate_array

jal allocate_array

# TODO: store return value ($v0) in variable array_dynamic

b read_input # go to read input if array length is valid

invalid_length:

li $v0, 4 # print error msg

la $a0, array_error_p

syscall

b create_array # branch back

read_input:

# TODO: load array base address into $a0

# TODO: load array length into $a1

# TODO: call subprogram read_array

jal read_array

# TODO: load array base address into $a0

# TODO: load array length into $a1

# TODO: call subprogram print_array

jal print_array

search_number:

li $v0, 4 # prompt user for a number

la $a0, number_prompt_p

syscall

li $v0, 5 # user input

syscall

beq $v0, $t9, search_index # branch to continue if user input -1

la $t7, array_dynamic # load array base address from

lw $a0, 0($t7) # static variable to $a0

la $t7, array_length # load array length from

lw $a1, 0($t7) # static variable to $a1

move $a2, $v0 # load user input to $a2

jal array_contains # jump to array_contains subprogram

move $t1, $v0 # move return value to $t1

bne $t1, $t9, exist # if return value != -1, branch to exist

li $v0, 4 # otherwise print not exist message

la $a0, not_exist_p

syscall

b search_number # branch back for another number

exist: