Question

Lab-3C   Pre-test Loop

Write a MIPS program to count the number of students who failed in a course. The final grades are given in an array. The fail grade is 60.

Example: Array and Output

     .data

NoOfStudents: 10

Values:   60 70 80 50 90 80 55 90 80 70

Output:

2 students failed

     .data

NoOfStudents: 12

Values:   60 70 80 50 90 80 55 90 80 70 55 80

Output:

3 students failed

Answer 1

Here is the MIPS code:
.text
main:
la $t0, NoOfStudents
lw $t0, 0($t0) #load the number of students
sll $t0, $t0, 2 #multiply the number of students by 4 (4 bytes in a word)
la $t1, Values #load the address of the array
li $t2, 0 #this is the array index, used for looping
li $t3, 0 #this is the counter for failed students
loop:
add $t4, $t1, $t2 #calculate loading address based on index
lw $t4, 0($t4) #load value from array
blt $t4, 60, incCounter #increment count if grade less than 60
j loopEnd
incCounter:
addi $t3, $t3, 1 #increment the counter
loopEnd:
addi $t2, $t2, 4 #increment the index by one word i.e. 4 bytes
blt $t2, $t0, loop #if end is not reached, loop again
move $a0, $t3 #print the answer
li $v0, 1
syscall
la $a0, printMessage #print the string for students failed
li $v0, 4
syscall
li $v0, 10 #exit the program
syscall
.data
NoOfStudents: .word 10
Values: .word 60 70 80 50 90 80 55 90 80 70
printMessage: .asciiz " students failed\n"

Here is a screenshot of the code:

.text main: la $to, Noofstudents lw $t0, 0($t0) #load the number of students sll $to, $to, 2 #multiply the number of students by 4 (4 bytes in a word) la $t1, Values #load the address of the array li $t2, 0 #this is the array index, used for looping li $t3, 0 #this is the counter for failed students loop: add $t4, $t1, $t2 #calculate loading address based on index lw $t4, 0($t4) #load value from array blt $t4, 60, incCounter #increment count if grade less than 60 j loopend incCounter: addi $t3, $t3, 1 #increment the counter loopEnd: addi $t2, $t2, 4 #increment the index by one word i.e. 4 bytes blt $t2, $to, loop #if end is not reached, loop again move $ao, $t3 #print the answer li svo, 1 syscall la $ao, printMessage #print the string for students failed li $v0, 4 syscall li $v0, 10 #exit the program syscall data Noofstudents: .word 10 Values: .word 60 70 80 50 90 80 55 90 80 70 printMessage: .asciiz " students failed\n"

Here is a screenshot of the output:

2 students failed

here is a screenshot of the output with the second array:

3 students failed

Comment in case of any doubts.