1- Write a MIPS program to copy a lowercase string to another string, converted
ID: 3788285 • Letter: 1
Question
1- Write a MIPS program to copy a lowercase string to another string, converted to uppercase. For example: “hola” should become “HOLA”. Store string lower as .asciiz and reserve space for string upper using .space. Look up an ASCII table in hex online or in the notes and notice the difference in hex between upper and lower case letters to figure out how to easily convert from one to the other. Your program should loop until it encounters the null terminator. Take a screen shot of the program code. Take another screen shot of the memory area after the program ran, but check the ASCII box below the memory window.
Table 1: Rubric for Problem 1
Task
Points
Code screen shot
10
Memory screen shot
5
Loop ends at ‘’
5
Code comments, formatting
5
Total
25
2- Rewrite your program in #1 to use a procedure for the conversion. In other words, if you send “apple” to the procedure it will return “APPLE”. Leave the rest of the code in main. Test it on the source strings: “loop2:” and “Elephant!” In other words, code in your main program calls the procedure twice, once for each source string. You should print a memory screen shot after the program runs, showing that both strings were converted – check the ASCII box.
You should add code to check if each byte is in fact a lowercase letter, and only convert if it is; otherwise it should just copy it.
In the program for problem 1 you could use $tn registers but in this program you should follow the conventions for using $sn and $tn registers.
Also, use the directive .space for the upper case strings, reserving at least 10 bytes for each of the 2 upper strings.
Table 2: Rubric for problem 2
Task
Points
Code and screen shot
5
Memory screen shots for 2 inputs
10
Correct procedure usage
5
Code checks a-z range
5
Correct use of $tn and $sn
5
Main code calls procedure twice
5
Code comments, formatting
5
Total
40
3- Single-step through your program through the first subroutine call and back, then answer the following questions. Copy a-g below and paste your answers/screen shot here.
a- What is the value of PC before you execute the jal?
b- What is the value of $ra before you execute the jal?
c- Set a breakpoint to the jr instruction and run until then. What is the value of PC before the jr?
d- Single step back to the main program. What address is in the next instruction?
e -What value is in the PC?
f- Write a 2-3 sentence summary describing how the PC and $ra registers change when a subroutine is called and when we return from a subroutine.
Table 3: Rubric for problem 3
Task
Points
a.
5
b.
5
c.
5
d.
5
e.
5
f.
10
Total
35
Task
Points
Code screen shot
10
Memory screen shot
5
Loop ends at ‘’
5
Code comments, formatting
5
Total
25
CS 3340 Computer Architecture Instructor: Karen Mazidi Homework 2: String manipulation, loops, branches, and subroutine calls in MIPS Background: asciiz stores a string with the null terminator 3 data 4 lower asci iz "hola 5 upper .asciiz ''xxxx'' 0x10010000 a l o h x x x 100 10 10 10 x ascii stores a string without a null terminator 3 data 4 lower ascii "hola 5 upper .ascii "xxxx" 0x10010000 a l o h x x x x Since MIPS stores a string as ASCII bytes, it will make sense to use the lbu/sb load/store byte instructions.Explanation / Answer
Answer
1.
.data
lower: .asciiz "hola "
upper: .asciiz "XXXX"
buffer: .space 80
.text
main:
la $a0, lower
li $t0, 0 # t0 = i = 0
FOR_loop:
slti $t1, $t0, 80 # t1 = 1 if and only if t0 < 80
beq $t1, $0, FOR_loop_end
slti $t2, $a0, 91
li $t3, 1
bne $t2, $t3, lower_to_upper
lower_to_upper:
subi $a0, $a0, 32 #subtracts 32 from the character value to change the case to upper
addi $t0, $t0, 1
j FOR_loop
FOR_loop_end:
#Prints the upper case string
li $v0, 4
la $a0, upper
syscall
#Prints the string entered by the user
la $a0, buffer
li $v0, 4
syscall
exit_Program: li $v0, 10 # system call to
syscall # terminate program
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