[SOLVED] Lab Sheet 4 for CS F342 Computer Architecture

Goals for the Lab: We build up on Lab 2 and Lab 3 and explore control (conditional) statements and loops. We also explore logical operations.

New Instructions:

1. bne application (beq, bgtz, bltz, bgez, blez are the other conditional branch opcodes )
2. Two groups of instructions: Branches and unconditional jump instructions.
3. Below are the list of instructions where the branching address is within 16 bits and register values are 32 bit
   • beq/ bne Branches if the quantities of two registers are equal / Not Equal.
   • bne Branches if the quantities of two registers are NOT equal.
   • bgtz / bgez / bltz / blez Branches if a quantity in a register is greater than zero / greater
   • than or equal to zero / less than zero / less than or equal to zero.

4. Below are the list of instructions where the branching address is within 26 bits.
   • j Jump to an address
   • jal Jump to an address, and store the return address in a register (for functions to be covered later).

5. Below are the list of instructions where the branching address is within 32 bits.
   • jr Jump to an address stored in a register
   • jalr Jump to an address stored in a register, and store the return address in another register (for functions to be covered later).

Exercise 1: Write MIPS Assembly code to find whether the input integer is even or odd.

Hint: Build up from Lab sheet 2, to read and integer into a register and then andi it with 0x1 (test for last bit as zero). Thereafter jump to report even if the result is zero.

# if $a0 has the value andi $a0, $a0, 1 bne $a0, $zero, odd_label

# print that the value is even j exit_label odd_label:

     # print that the value is odd exit_label:       li $v0, 10 # exit program       syscall

Exercise 2: Write MIPS Assembly code to find the length of the given string. Presently the string is coming from labelled data. Modify the code below to use j (Jump) and beq instead of bne.

.data

mystr : .asciiz “This is given string”

 .text

main: la $a0, mystr # find the strlen for string at this address       li $v0, -1    # $v0 has length start at 1 because ‘\0’ counted below

slen_0: lb $t0, ($a0)    # load current byte, move to next         addi $a0, $a0, 1

        addi $v0, $v0, 1 # but first increment result

        bne $t0, $zero, slen_0 # if current byte isn’t ‘\0’, repeat

      move $a0, $v0          # display result of strlen       li $v0, 1

      syscall

      li $v0, 10 # exit program       syscall

Exercise 3: Write MIPS Assembly code to print all the multiples of the given number between 0 and 100. Your program should allow the user to give the input number. Sample test case : Input: 25 : Output: 25 50 75

Hint: For loop implementation you can use pseudo instructions given below.

Exercise 4: Decode (disassemble) the following instructions.

1. 12640007
2. 08100010
3. 08100010
4. 1d600004
5. 05400003 6. 05210002
6. 19000001