Allocating Memory for a Node

Dynamic memory can be used for a node. Here is a program that creates the two-node linked list of the picture:

#
# create the first node 
li      $v0,9             # allocate memory
li      $a0,8             # 8 bytes
syscall                   # $v0 <-- address
move    $s1,$v0           # $s1 = &(first node)
li      $t0,1             # store 1
sw      $t0,0($s1)        # at displacement 0
                          # & == "address of"

# create the second node 
li      $v0,9             # allocate memory
li      $a0,8             # 8 bytes
syscall                   # $v0 <-- address
move    $s2,$v0           # $s2 = &(second node)
                          # & == "address of"

# link the second node to the first
sw    ,4()       # copy address of second node
                          # into the first node

# initialize the second node
li      $t0,2             # store 2
sw      $t0,0($s2)        # at displacement 0

# put null in the link of the second node
sw    ,4()

First, 8 bytes are dynamically allocated for the first node. The address of the node is saved in $s1. The data, "1", is copied into the first four bytes of the node at displacement 0 off of $s1.

The process is repeated for the second node, except that its address is saved in $s2.

To complete the structure, the first node is made to point to the second node. This is what the green arrow between the nodes shows. Also, a null should be put in the pointer field of the last node. But the code is not complete.

Answer:

Allocating Memory for a Node

QUESTION 4: