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#include "qutyio.h$"$

$/**$ Tutorial $06$

INTRODUCTION:

In this week's tutorial you will implement a pseudorandom number

generator. This will be of particular relevance to Assessment $2.$

$*/$

$/**$ EX: $6\mathrm{.}0$

TASK: Define a global unsigned $32-$bit integer called "state".

Initialise "state" with a value equal to your student number, where each

decimal digit in your student number represents a hexadecimal literal.

EXAMPLE: If your student number was n$12345678$ then you should assign the

value $0$x$12345678$ to "state".

Once you have defined this variable uncomment the first printf$()$

statement in the main$()$ function.

$*/$

$/**$ CODE: Write your code for Ex $6\mathrm{.}0$ above this line. $*/$

$/**$ EX: $6\mathrm{.}1$

TASK: Write the function prototype for a function called "next"

which takes no parameters and returns no result.

$*/$

$/**$ CODE: Write your code for Ex $6\mathrm{.}1$ above this line. $*/$

$/**$ EX: $6\mathrm{.}2$

TASK: Write a function called "print$\_$rand" which returns no result

and takes, as a single argument, a pointer to an unsigned $32-$bit

integer.

The function should inspect the least significant two bits of the

integer pointed to by the argument, and depending on the value of the

bits, execute one of the following function calls:

$0$b$00(0)$: putchar$(\text{'}1\text{'})$;

$0$b$01(1)$: putchar$(\text{'}2\text{'})$;

$0$b$10(2)$: putchar$(\text{'}3\text{'})$;

$0$b$11(3)$: putchar$(\text{'}4\text{'})$;

Once you have written this function uncomment the second printf$()$

statement in the main$()$ function.

$*/$

$/**$ CODE: Write your code for Ex $6\mathrm{.}2$ above this line. $*/$

$/**$ EX: $6\mathrm{.}3$

TASK: Complete the implementation for the next$()$ function.

next$()$ should:

$1.$ Right shift the bits in "state" by $1$ position.

$2.$ If the bit shifted out of state in step $1$ was set $(1),$ take the XOR

of "state" with $0$xA$8$E$831$E$0$ and store the result in "state".

Once you have written this function uncomment the third printf$()$

statement in the main$()$ function.

$*/$

void next$($void$)$

$\{$

$/**$ CODE: Write your code for Ex $6\mathrm{.}3$ within this function. $*/$

$\}$

int main$($void$)$

$\{$

serial$\_$init$()$;

$/**$ TODO: Uncomment the line below after Ex $6\mathrm{.}0$ is completed. $*/$

$//$ printf$("$Ex $6\mathrm{.}0$: state $=0$x$\%08$lX

$",$ state$)$;

$/**$ TODO: Uncomment the line below after Ex $6\mathrm{.}2$ is completed. $*/$

$//$ uint$32\_$t test $=0$b$1100$; printf$("$Ex $6\mathrm{.}2$: output $=")$; print$\_$rand$($&test$)$; test $>>=1$; print$\_$rand$($&test$)$; test $>>=1$; print$\_$rand$($&test$)$; test $>>=1$; print$\_$rand$($&test$)$; printf$("$

$")$;

$/**$ TODO: Uncomment the line below after Ex $6\mathrm{.}3$ is completed. $*/$

$//$ next$()$; printf$("$Ex $6\mathrm{.}3$: state $=0$x$\%08$lX$",$ state$)$; next$()$; next$()$; next$()$; next$()$; printf$(",$ state $=0$x$\%08$lX

$",$ state$)$;

$/**$ EX: $6\mathrm{.}4$

The variable "state" together with the next$()$ function implement a

linear$-$feedback shift register, which produces a pseudorandom number

sequence.

This sequence was seeded $($initialised$)$ with your student number.

TASK: Write code below to print the next $32$ digits derived from this

pseudorandom number sequence using next$()$ and print$\_$rand$().$

All digits should be printed on a single line without spaces.

NOTE: Call next$()$ to advance "state" prior to printing the first

digit.

TIP: Recall that the unary operator $"$&$"$ can be used to get a

reference $($pointer$)$ to some data.

$*/$

printf$("$Ex $6\mathrm{.}4$: $")$;

$/**$ CODE: Write your code for Ex $6\mathrm{.}4$ below this line. $*/$

$/**$ CODE: Write your code for Ex $6\mathrm{.}4$ above this line. $*/$

printf$("$

$")$;

$//$ END OF TUTORIAL$06$ EXERCISES $//$

$//$ DO NOT EDIT BELOW THIS LINE $//$

while $(1)$

; $//$ Loop indefinitely

$\}$