Computer Technology 2 Practice/Coding

Question 1

W6 Given the following:
The address of stackPtr is x:08
The address of tPtr is x:12
The address of tempPtr is x:24
The address of newPtr is x:16
The address of info is: x:20
Implement the following
Add node 1 : content 3; address is X:30
Add node 2: contents 6; address is X:36
Add node 3: contents 10; address is X:40
Delete all the nodes
Illustrate the stack by showing contents of tempPtr/stackPtr, newPtr and tPtr: after each of the above steps.

StackNode* stackPtr = NULL;
int value;

push(&stackPtr, value);
void push(StackNode* topPtr, int info)
StackNode newPtr = malloc(sizeof(StackNode));

// insert the node at stack top
if (newPtr != NULL) {
newPtr->data = info;
newPtr->nextPtr = *topPtr;
*topPtr = newPtr;

pop(&stackPtr));
int pop(StackNode* *topPtr)

StackNode* tempPtr = * topPtr;
int popValue = (* topPtr)->data;
* topPtr = (* topPtr)->nextPtr;
free(tempPtr);

Question 2

W6 Explain, using examples (include node addresses), how to implement the push and pop functions of a stack (15 marks)

Question 3

W6 Explain, using an example (include addresses), if this function would push a node on a stack (9 marks)

//fnt 1 call
Push (&StackPtr);

void push(StackNode** topPtr, int info)
{
StackNode newPtr = malloc(sizeof(StackNode));

if (newPtr != NULL) {
newPtr->data = info;
newPtr->nextPtr = topPtr;
topPtr = newPtr;
}
else {
printf(“%d not inserted. No memory available.\n”, info);
}
}

Question 4

W6 Explain what the following code does and if it would pop a value from the stack (9 Marks)

// function to pop values from stack assuming it is not empty
int pop(StackNode** topPtr)
{
if (topPtr != Null){
StackNode* tempPtr = topPtr;
int popValue = (topPtr)->data;
topPtr = (topPtr)->nextPtr;
free(tempPtr);
return popValue;
}
else return ‘\0’;

Question 5

W7 Explain, using examples (include node addresses), how to implement the enqueue and dequeue functions of a queue (15 marks)

Question 6

W7 Explain if following Queue “enqueue” function will add a node to a queue (10 marks)

void enqueue(QueueNode* * headPtr, QueueNode* * tailPtr, char value)
{
QueueNodeP*newPtr = malloc(sizeof(QueueNode));

if (newPtr != NULL) {
newPtr->data = value;
newPtr->nextPtr = NULL;

if (isEmpty(*headPtr)) {  // function to check if  queue is empty 
     headPtr = newPtr;
  } 
  else {
     (tailPtr)->nextPtr = newPtr;
  } 
  tailPtr = newPtr;    }     else {
  printf("%c not inserted. No memory available.\n", value);    }  }

Question 7

W7 Explain what the following code does and if it will not dequeue successfully (10 marks)

char fnt1(QueueNode** headPtr, QueueNode** tailPtr)
{
if (headPtr != NULL){
char value = (headPtr)->data;
QueueNode* tempPtr = headPtr;
headPtr = (*headPtr)->nextPtr;

if (*headPtr == NULL) {
tailPtr = NULL;
}

free(tempPtr);
return value;
}
Else
Printf(“bla bla bla….”);
}

Question 8

W8 Explain, using an example such as “ls –l –a” how the following code using a combination of the fork(), wait() and exec() command can be used to run new processes. (12 marks)

if ((pid = fork()) < 0) { /* fork a child process /
printf(“** ERROR: forking child process failed\n”);
exit(42);
}
else if (pid == 0) { /* for the child process: /
if (execvp(argv, argv) < 0) { /* execute the command /
printf(“** ERROR: exec failed\n”);
exit(1);
}
}
else { /* for the parent: /
while (wait(&status) != pid) / wait for completion */
;
}

Question 9

W8 Explain, in your own words, the above code. (argc, thread_create parameters, thread join and thread code: cast void*, calculation and why the result can be displayed in function main) (10 marks)

SLIDE 32 - THREADS

Question 10

W8 What would be the output of the code for the following commandline argc: (4 marks)
./CLargthread 10
./Clargthread 5 12
./CLargthread

SLIDE 32 - THREADS

Question 11

W8 Explain, using sample output, what will happen if the join statement is removed and the commandline arguments are:
./Clargthread 5 (4 marks)

SLIDE 32 - THREADS

Question 12

W9 Producer/consumer problem. Explain does this code prevent/result in deadlock (8 marks)

SLIDE 38

Question 13

W10 Explain, using conventional deadlock modelling, if the following schedule result in deadlock: (6 marks)

SLIDE 35

Question 14

W10 Fig A and Fig B show directed resource graphs for three processes (P1, P2 and P3 and three sources (R1, R2, R3). Using the detection/reduction algorithm Explain: For each of the above diagrams show: (14 marks)
If Is it deadlocked?
What is the result after reduction?
Which, if any processes are deadlocked

SLIDE 36

Question 15

W10 Using Bankers algorithm answer the following:

How many resources of type A, B, C and D are there?
What are the contents of the Need matrix?
Is the system in a safe state? Provide reasoning for your answer (show the sequence in which the processes would finish)
If a request from process P2 arrives for additional resources of {0, 2, 0, 0}, can the Bankers algorithm grant the request immediately? Provide reasoning for your answer. (14 Marks)

SLIDE 37

Question 16

W11 Using a demand page memory management system how many page faults will be generate by the following sequence and page frame numbers for the first in first out/least recently used? Clearly show (Explain) how you arrived at the answer. (12 marks)

Reference Sequence = [A,B, C, B, D, A, E, F, B, E, D, F].

Using 3 page frames
Using 4 page frames.