initial commit

9 files changed, 1224 insertions, 0 deletions

diff --git a/comp1521/cellular/cellular.s b/comp1521/cellular/cellular.s
new file mode 100644
index 0000000..3bdd7aa
--- /dev/null
+++ b/comp1521/cellular/cellular.s
@@ -0,0 +1,362 @@
+########################################################################
+# COMP1521 20T2 --- assignment 1: a cellular automaton renderer
+
+# Complex logical statements are marked with horizontal bars for readability.
+
+# Maximum and minimum values for the 3 parameters.
+
+MIN_WORLD_SIZE	=    1
+MAX_WORLD_SIZE	=  128
+MIN_GENERATIONS	= -256
+MAX_GENERATIONS	=  256
+MIN_RULE	=    0
+MAX_RULE	=  255
+
+# Characters used to print alive/dead cells.
+
+ALIVE_CHAR	= '#'
+DEAD_CHAR	= '.'
+
+# Maximum number of bytes needs to store all generations of cells.
+
+MAX_CELLS_BYTES	= (MAX_GENERATIONS + 1) * MAX_WORLD_SIZE
+
+	.data
+
+# `cells' is used to store successive generations.  Each byte will be 1
+# if the cell is alive in that generation, and 0 otherwise.
+
+cells:	.space MAX_CELLS_BYTES
+#cells:	.byte 1:MAX_CELLS_BYTES           # Very useful for debugging.
+
+# Some strings you'll need to use:
+
+prompt_world_size:	.asciiz "Enter world size: "
+error_world_size:	.asciiz "Invalid world size\n"
+prompt_rule:		.asciiz "Enter rule: "
+error_rule:		.asciiz "Invalid rule\n"
+prompt_n_generations:	.asciiz "Enter how many generations: "
+error_n_generations:	.asciiz "Invalid number of generations\n"
+
+	.text
+
+    # REGISTERS IN MAIN
+    # $s0: int world_size    (runtime input)
+    # $s1: int rule          (runtime input)
+    # $s2: int n_generations (runtime input)
+    # $s3: int reverse       (0 or 1)
+    # $s4: int g             (loop counters)
+    # $t0 to $t2             (temp variables)
+    # $v0 to $v2             (syscalls and functions)
+
+#--------------------------------BEGIN_MAIN-------------------------------------
+
+main:
+    # No need to store $ra on the stack until we call our own functions.
+
+    la      $a0, prompt_world_size      # printf("Enter world size: ");
+    li      $v0, 4
+    syscall
+    
+    move    $s0, $zero                  # $s0: int world_size = 0;
+    li      $v0, 5                      # scanf("%d", &world_size);
+    syscall
+    move    $s0, $v0
+
+    blt     $s0, MIN_WORLD_SIZE, if0    # if (world_size < MIN_WORLD_SIZE)
+    bgt     $s0, MAX_WORLD_SIZE, if0    # ^|| (world_size > MAX_WORLD_SIZE);
+    b       skip0
+if0:
+    la      $a0, error_world_size       # printf("Invalid world size\n");
+    li      $v0, 4
+    syscall
+    li      $v0, 1                      # return 1;
+    jr      $ra
+    # Despite returning 1, echo $? says '0'. I suspect this is due to spim
+    # returning 0 on the "successful" execution of a program. I am unaware
+    # of how to extract the return value of an emulated mips program.
+
+skip0:
+    la      $a0, prompt_rule            # printf("Enter rule: ");
+    li      $v0, 4
+    syscall
+    
+    move    $s1, $zero                  # $s1: int rule = 0;
+    li      $v0, 5                      # scanf("%d", &world_size);
+    syscall
+    move    $s1, $v0
+
+    blt     $s1, MIN_RULE, if1          # if (world_size < MIN_RULE)
+    bgt     $s1, MAX_RULE, if1          # ^|| (world_size > MAX_RULE);
+    b       skip1
+if1:
+    la      $a0, error_rule             # printf("Invalid world size\n");
+    li      $v0, 4
+    syscall
+    li      $v0, 1                      # return 1;
+    jr      $ra
+
+skip1:
+    la      $a0, prompt_n_generations   # printf("Enter how many generations ");
+    li      $v0, 4
+    syscall
+    
+    move    $s2, $zero                  # $s2: n_generations = 0;
+    li      $v0, 5                      # scanf("%d", &world_size);
+    syscall
+    move    $s2, $v0
+
+    blt     $s2, MIN_GENERATIONS, if2   # if (n_generations < MIN_GENERATIONS)
+    bgt     $s2, MAX_GENERATIONS, if2   # ^|| (n_generations > MAX_GENERATIONS);
+    b       skip2
+if2:
+    la      $a0, error_n_generations    # printf("Invalid world size\n");
+    li      $v0, 4
+    syscall
+    li      $v0, 1                      # return 1;
+    jr      $ra
+
+skip2:
+    li      $a0, '\n'                   # putchar('\n');
+    li      $v0, 11
+    syscall
+
+    move    $s3, $zero                  # $s3: int reverse = 0;
+    blt     $s2, 0, if3                 # if (n_generations < 0);
+    b       skip3
+if3:
+    li      $s3, 1                      # reverse = 1;
+    mul     $s2, $s2, -1                # n_generations = -n_generations;
+
+skip3:
+    la      $t0, cells                  # cells[0][world_size / 2] = 1;
+    li      $t1, 2
+    div     $s0, $t1
+    mflo    $t1
+    add     $t0, $t0, $t1
+    li      $t2, 1
+    sb      $t2, ($t0)
+
+    # After this point we begin to use our functions, so save the stack pointer.
+    sub     $sp, $sp, 4
+    sw      $ra, ($sp)
+
+
+#-------------------------------FIRST_LOOP_START--------------------------------
+    
+    li      $s4, 1                      # for (int g = 1; ($s4: int g = 1)
+loop0:
+    bgt     $s4, $s2, end0              # ^g <= n_generations; (test condition)
+    
+    move    $a0, $s0                    #run_generation(world_size, g, rule);
+    move    $a1, $s4
+    move    $a2, $s1
+    jal     run_generation
+    
+    add     $s4, $s4, 1                 # g++;);   (increment)
+    b       loop0
+end0:
+
+#--------------------------------FIRST_LOOP_END---------------------------------
+#--------------------------------------IF---------------------------------------
+
+    beqz    $s3, skip4                  # if (reverse)
+
+#------------------------------SECOND_LOOP_START--------------------------------
+    move    $s4, $s2                    # for (int g = n_generations; 
+                                        # ($s4: int g = n_generations)
+
+loop1:
+    blt     $s4, 0, end1                # ^g >= 0; (test condition)
+
+    move    $a0, $s0                    # print_generation(world_size, g);
+    move    $a1, $s4
+    jal     print_generation 
+    
+    sub     $s4, $s4, 1                 # g--;);   (decrement)
+    b       loop1
+end1:
+#------------------------------SECOND_LOOP_END----------------------------------
+    b       skip5 
+#------------------------------------ELSE---------------------------------------
+skip4:                                  # else
+#------------------------------THIRD_LOOP_START---------------------------------
+    li      $s4, 0                      # for (int g = 0; ($s4: int g = 0)
+loop2:
+    bgt     $s4, $s2, end2              # ^g <= n_generations; (test_condition) 
+
+    move    $a0, $s0                    # print_generation(world_size, g);
+    move    $a1, $s4
+    jal     print_generation 
+
+    add     $s4, $s4, 1                 # g++;) (increment)
+    b       loop2
+
+end2:
+#-------------------------------THIRD_LOOP_END----------------------------------
+skip5:
+#----------------------------------ELSE_END-------------------------------------
+
+	lw      $ra, ($sp)                  # Load $ra from the stack.
+    add     $sp, $sp, 4                 # Deallocate from the stack, now empty.
+    li      $v0, 0                      # Return 0.
+	jr      $ra
+#----------------------------------MAIN_END-------------------------------------
+
+
+	# Given `world_size', `which_generation', and `rule', calculate
+	# a new generation according to `rule' and store it in `cells'.
+
+    # REGISTERS IN RUN_GENERATION
+    # $a0: int world_size                (passed to function)
+    # $a1: int which_generation          (passed to function)
+    # $a2: int rule                      (passed to function)   
+    # $t0: int x                         (copy of arguments)    CHANGED!
+    # $t1: int left                      (copy of arguments)    CHANGED!
+    # $t2: int centre                    (copy of arguments)    CHANGED!
+    # $t3: int right                     (increment variable)   CHANGED!
+    # $t4 to $t5:                        (temp variables)       CHANGED!
+    # $v0: int                           (syscalls)             CHANGED!
+
+#-----------------------------BEGIN_FUNCTION_0----------------------------------
+run_generation:
+
+    # In this function we are pressed for variables. We will modify $a variables
+    # but continue to preserve them without using the stack as they are
+    # easily reversible changes which we may keep track of and fix before we
+    # return.
+
+#---------------------------------BEGIN_LOOP------------------------------------
+    li      $t0, 0                      # for(int x = 0; ($t0: int x = 0)
+f0loop0:
+    bge     $t0, $a0, f0end0            # ^x < world_size
+
+    li      $t1, 0                      # $t1: int left = 0;
+
+    sub     $a1, $a1, 1                 # which_generation--
+    sub     $t0, $t0, 1                 # x--
+
+    la      $t2, cells                  # $t3 = &cells[which_generation-1][x-1]
+    mul     $t3, $a1, MAX_WORLD_SIZE
+    add     $t3, $t2, $t3
+    add     $t3, $t3, $t0
+
+    add     $t0, $t0, 1                 # x++
+    ble     $t0, 0, f0skip0             # if (x > 0)
+    lb      $t1, ($t3)                  # left = cells[which_generation-1][x-1]
+
+f0skip0:
+    add     $t3, $t3, 1                 # ++t3, access [x] not [x-1]
+    lb      $t2, ($t3)                  # $t2 = cells[which_generation-1][x]
+    
+    add     $t4, $t3, 1                 # copy useful ++$t3 before we use $t3
+
+    li      $t3, 0                      # $t3: int right = 0
+    sub     $a0, $a0, 1                 # world_size--
+    bge     $t0, $a0, f0skip1
+    
+    lb      $t3, ($t4)                  # right = cells[which_generation-1][x+1]
+f0skip1:
+    add     $a0, $a0, 1                 # world_size++
+    add     $a1, $a1, 1                 # which_generation++
+    
+    sll     $t1, $t1, 2                 # int state = left << 2 | centre << 1
+    sll     $t2, $t2, 1                 # ^ | right << 0;
+    or      $t5, $t1, $t2               
+    or      $t5, $t5, $t3
+
+    li      $t1, 1
+    sll     $t5, $t1, $t5               # int bit = 1 << state;
+    and     $t5, $a2, $t5               # int set = rule & bit;
+
+    la      $t2, cells                  # $t2 = &cells[which_generation][x]
+    mul     $t3, $a1, MAX_WORLD_SIZE    
+    add     $t3, $t2, $t3
+    add     $t3, $t3, $t0
+    
+#--------------------------------------IF---------------------------------------
+    beqz    $t5, f0skip2                # if (set)
+
+    li      $t1, 1                      # cells[which_generation][x] = 1;
+    sb      $t1, ($t3)
+
+    b       f0skip3
+f0skip2:
+#------------------------------------ELSE---------------------------------------
+    li      $t1, 0                      # cells[which_generation][x] = 0;
+    sb      $t1, ($t3)
+f0skip3:
+
+    add     $t0, $t0, 1                 # x++ (increment)
+    b       f0loop0
+#-----------------------------------END_ELSE------------------------------------
+f0end0:
+#-----------------------------------END_LOOP------------------------------------
+	jr	$ra                             # return;
+#-------------------------------END_FUNCTION_0----------------------------------
+
+	# Given `world_size', and `which_generation', print out the
+	# specified generation.
+
+    # REGISTERS IN PRINT_GENERATION
+    # $a0: int world_size                (passed to function)   CHANGED!
+    # $a1: int which_generation          (passed to function)
+    # $t0: int world_size                (copy of arguments)    CHANGED!
+    # $t1: int which_generation          (copy of arguments)    CHANGED!
+    # $t2: int x                         (0++, loop counter)    CHANGED!
+    # $t3 to $t4:                        (temp variables)       CHANGED!
+    # $v0                                (syscalls)             CHANGED!
+
+#-----------------------------BEGIN_FUNCTION_1----------------------------------
+print_generation:
+    move    $t0, $a0                    # Copy arguments, to use syscalls.
+    move    $t1, $a1
+
+    move    $a0, $t1                    # printf("%d", which_generation);
+    li      $v0, 1
+    syscall
+
+    li      $a0, '\t'                   # putchar('\t');
+    li      $v0, 11
+    syscall
+
+#-------------------------------FOR_LOOP_START----------------------------------
+    li      $t2, 0                      # for (int x = 0; ($t2: int x = 0)
+f1loop0:
+    bge     $t2, $t0, f1end0            # ^x < world_size; (test condition)
+
+#-------------------------------------IF----------------------------------------
+    la      $t3, cells                  # if(cells[which_generation][x])
+    mul     $t4, $t1, MAX_WORLD_SIZE
+    add     $t4, $t4, $t2
+    add     $t4, $t4, $t3
+    lb      $t4, ($t4)
+    beqz    $t4, f1skip0
+
+    li      $a0, ALIVE_CHAR             # putchar(ALIVE_CHAR);
+    li      $v0, 11
+    syscall
+    b       f1skip1
+
+
+f1skip0:
+#------------------------------------ELSE---------------------------------------
+    li      $a0, DEAD_CHAR              # putchar(DEAD_CHAR);
+    li      $v0, 11
+    syscall
+
+
+f1skip1:
+#----------------------------------ELSE_END-------------------------------------
+    add     $t2, $t2, 1                 # x++;);   (increment)
+    b       f1loop0
+f1end0:
+
+#--------------------------------FOR_LOOP_END-----------------------------------
+
+    li      $a0, '\n'                   # putchar('\n');
+    li      $v0, 11
+    syscall
+
+	jr	$ra                             # return;
+#-------------------------------END_FUNCTION_1----------------------------------
diff --git a/comp1521/cellular/reference.c b/comp1521/cellular/reference.c
new file mode 100644
index 0000000..217275f
--- /dev/null
+++ b/comp1521/cellular/reference.c
@@ -0,0 +1,218 @@
+////////////////////////////////////////////////////////////////////////
+// COMP1521 20T2 --- assignment 1: a cellular automaton renderer
+//
+// This code runs a one-dimensional, three-neighbour cellular automaton.
+// It examines its neighbours and its value in the previous generation
+// to derive the value for the next generation.
+//
+//     . . . . # . . . .
+//     . . . # # # . . .
+//     . . # # . . # . .
+//     . # # . # # # # .
+//     # # . . # . . . #
+//
+// Here, we using '#' to indicate a cell that's alive; and '.' to
+// indicate a cell that is not.
+//
+// Given we examine three neighbours, there are eight states that the
+// prior cells could be in.  They are:
+//
+//     . . .   . . #   . # .   . # #   # . .   # . #   # # .   # # #
+//       0       1       2       3       4       5       6       7
+//
+// For each one, we decide what action to take.  For example, we might
+// choose to have the following `rule':
+//
+//     . . .   . . #   . # .   . # #   # . .   # . #   # # .   # # #
+//       .       #       #       #       #       .       .       .
+//
+// We apply this rule to every cell, to determine whether the next state
+// is alive or dead; and this forms the next generation.  If we print
+// these generations, one after the other, we can get some interesting
+// patterns.
+//
+// The description of the rule above --- by example, showing each case
+// and how it should be handled --- is inefficient.  We can abbreviate
+// this rule by reading it in binary, considering live cells as 1's and
+// dead cells as 0s; and if we consider the prior states to be a binary
+// value too --- the above rule could be 0b00001110, or 30.
+//
+// To use that rule, we would mix together the previous states we're
+// interested in --- left, middle, and right --- which tells us which
+// bit of the rule value gives our next state.
+//
+// The world size, rule and the number of generations, are read from stdin:
+//
+// $ ./cellular
+// Enter world size: 60
+// Enter rule: 30
+// Enter how many generations: 10
+//
+//       0     ..............................#.............................
+//       1     .............................###............................
+//       2     ............................##..#...........................
+//       3     ...........................##.####..........................
+//       4     ..........................##..#...#.........................
+//       5     .........................##.####.###........................
+//       6     ........................##..#....#..#.......................
+//       7     .......................##.####..######......................
+//       8     ......................##..#...###.....#.....................
+//       9     .....................##.####.##..#...###....................
+//       10    ....................##..#....#.####.##..#...................
+//
+// $ ./cellular
+// Enter world size: 60
+// Enter rule: 30
+// Enter how many generations: -10
+//
+// 10   ....................##..#....#.####.##..#...................
+// 9    .....................##.####.##..#...###....................
+// 8    ......................##..#...###.....#.....................
+// 7    .......................##.####..######......................
+// 6    ........................##..#....#..#.......................
+// 5    .........................##.####.###........................
+// 4    ..........................##..#...#.........................
+// 3    ...........................##.####..........................
+// 2    ............................##..#...........................
+// 1    .............................###............................
+// 0    ..............................#.............................
+
+#include <stdio.h>
+#include <stdint.h>
+
+// maximum and minimum values for the 3 parameters
+
+#define MIN_WORLD_SIZE     1
+#define MAX_WORLD_SIZE   128
+#define MIN_GENERATIONS -256
+#define MAX_GENERATIONS  256
+#define MIN_RULE           0
+#define MAX_RULE         255
+
+// characters used to print alive/dead cells
+
+#define ALIVE_CHAR        '#'
+#define DEAD_CHAR         '.'
+
+// `cells' is used to store successive generations.  Each byte will be 1
+// if the cell is alive in that generation, and 0 otherwise.
+
+static int8_t cells[MAX_GENERATIONS + 1][MAX_WORLD_SIZE];
+
+static void run_generation(int world_size, int which_generation, int rule);
+static void print_generation(int world_size, int which_generation);
+
+int main(int argc, char *argv[]) {
+
+    // read 3 integer parameters from stdin
+
+    printf("Enter world size: ");
+    int world_size = 0;
+    scanf("%d", &world_size);
+    if (world_size < MIN_WORLD_SIZE || world_size > MAX_WORLD_SIZE) {
+        printf("Invalid world size\n");
+        return 1;
+    }
+
+    printf("Enter rule: ");
+    int rule = 0;
+    scanf("%d", &rule);
+    if (rule < MIN_RULE || rule > MAX_RULE) {
+        printf("Invalid rule\n");
+        return 1;
+    }
+
+    printf("Enter how many generations: ");
+    int n_generations = 0;
+    scanf("%d", &n_generations);
+    if (n_generations < MIN_GENERATIONS || n_generations > MAX_GENERATIONS) {
+        printf("Invalid number of generations\n");
+        return 1;
+    }
+
+    putchar('\n');
+
+    // negative generations means show the generations in reverse
+    int reverse = 0;
+    if (n_generations < 0) {
+        reverse = 1;
+        n_generations = -n_generations;
+    }
+
+    // the first generation always has a only single cell which is alive
+    // this cell is in the middle of the world
+    cells[0][world_size / 2] = 1;
+
+    for (int g = 1; g <= n_generations; g++) {
+        run_generation(world_size, g, rule);
+    }
+
+    if (reverse) {
+        for (int g = n_generations; g >= 0; g--) {
+            print_generation(world_size, g);
+        }
+    } else {
+        for (int g = 0; g <= n_generations; g++) {
+            print_generation(world_size, g);
+        }
+    }
+
+    return 0;
+}
+
+//
+// Calculate a new generation using rule and store it in cells
+//
+static void run_generation(int world_size, int which_generation, int rule) {
+    for (int x = 0; x < world_size; x++) {
+
+        // Get the values in the left and right neighbour cells.
+        // This requires some care, otherwise we could read beyond the
+        // bounds of the array.  In the cases we are at the limits of
+        // the function, we consider those out-of-bounds cells zero.
+
+        int left = 0;
+        if (x > 0) {
+            left = cells[which_generation - 1][x - 1];
+        }
+
+        int centre = cells[which_generation - 1][x];
+
+        int right = 0;
+        if (x < world_size - 1) {
+            right = cells[which_generation - 1][x + 1];
+        }
+
+        // Convert the left, centre, and right states into one value.
+        int state = left << 2 | centre << 1 | right << 0;
+
+        // And check whether that bit is set or not in the rule.
+        // by testing the corresponding bit of the rule number.
+        int bit = 1 << state;
+        int set = rule & bit;
+
+        if (set) {
+            cells[which_generation][x] = 1;
+        } else {
+            cells[which_generation][x] = 0;
+        }
+    }
+}
+
+//
+// Print out the specified generation
+//
+static void print_generation(int world_size, int which_generation) {
+    printf("%d", which_generation);
+    putchar('\t');
+
+    for (int x = 0; x < world_size; x++) {
+        if (cells[which_generation][x]) {
+            putchar(ALIVE_CHAR);
+        } else {
+            putchar(DEAD_CHAR);
+        }
+    }
+
+    putchar('\n');
+}
diff --git a/comp1521/smips/helper.c b/comp1521/smips/helper.c
new file mode 100644
index 0000000..ebe798b
--- /dev/null
+++ b/comp1521/smips/helper.c
@@ -0,0 +1,54 @@
+#include "helper.h"
+
+// Returns the n'th bit of a uint32_t value.
+uint32_t get_nth_bit(const uint32_t value, const int n) {
+    return (value & (1u << n)) >> n;
+}
+
+// Prints the bits of a uint32_t value.
+void print_bits(const uint32_t value) {
+    for (int i = (int)sizeof(uint32_t)*8-1; i >= 0; --i) {
+        printf("%d", get_nth_bit(value, i));
+    }
+    printf("\n");
+}
+
+// Skips past the next newline. 
+// If EOF, stays on EOF so that subsequent fgetc() calls return EOF.
+void skip_past_newline(FILE *const fptr) {
+    int c = 0;
+    c = fgetc(fptr);
+    while (true) {
+        if (c == EOF) {
+            fseek(fptr, -1L, SEEK_CUR);
+            return;
+        }
+        else if (c == '\n') {
+            printf("newline\n");
+            return;
+        } else {
+            fseek(fptr, -1L, SEEK_CUR);
+            return;
+        }
+        printf("skipping char\n");
+        c = fgetc(fptr);
+    }
+}
+
+// Converts decimal values to hex obviously.
+uint32_t hex_to_decimal(const uint32_t decimal) {
+    uint32_t ret = 0;
+    for (size_t i = 0; i < sizeof(uint32_t); ++i) { // Iterate through 4 bytes.
+        uint32_t tmp = (decimal & (0xFFu << 8*i)) >> 8*i;
+        if (isalpha(tmp)) {
+            tmp -= 'a';
+            tmp += 10;
+        }
+        else if (isdigit(tmp)) {
+            tmp -= '0';
+        } 
+        // There should be no other cases if the input is hex.
+        ret |= (tmp << 4*i);
+    }
+    return ret;
+}
diff --git a/comp1521/smips/input.c b/comp1521/smips/input.c
new file mode 100644
index 0000000..0932978
--- /dev/null
+++ b/comp1521/smips/input.c
@@ -0,0 +1,52 @@
+#include "input.h"
+
+// Converts decimal values of a uint32_t argument to hex.
+uint32_t hex_to_decimal(const uint32_t decimal) {
+    uint32_t ret = 0;
+    for (size_t i = 0; i < sizeof(uint32_t); ++i) { // Iterate through 4 bytes.
+        uint32_t tmp = (decimal & (0xFFu << 8 * i)) >> 8 * i;
+        if (isalpha(tmp)) {
+            tmp -= 'a';
+            tmp += 10;
+        } else if (isdigit(tmp)) {
+            tmp -= '0';
+        }
+        // There should be no other cases if the input is hex.
+        ret |= (tmp << 4 * i);
+    }
+    return ret;
+}
+
+// Returns the next instruction in hex. Returns 0 if EOF reached.
+uint32_t get_next_instruction(FILE *const iptr) {
+    uint32_t ret = 0;
+    int i = 0;
+    for (int c = fgetc(iptr); c != '\n'; c = fgetc(iptr), ++i) {
+        if (c == EOF) {
+            return 0u;
+        }
+        uint32_t tmp = hex_to_decimal((uint32_t)c);
+        ret |= (tmp << (28 - i * 4));
+    }
+    // We have to take into account the potential for the hex value to not be
+    // "full", ie we may read abc instead of 00000abc.
+    ret >>= (32 - i * 4);
+    return ret;
+}
+
+// Sets the iptr to the previous instruction, which sits on the newline so that
+// later calls to get_next_instruction work as expected.
+// Also, if unable to find a previous instruction, sets the iptr to EOF.
+void goto_previous_instruction(FILE *const iptr) {
+    int c = 0;
+    fseek(iptr, -2L, SEEK_CUR);
+    while (ftell(iptr)) {
+        c = fgetc(iptr);
+        if (c == '\n') {
+            return;
+        }
+        fseek(iptr, -2L, SEEK_CUR);
+    }
+    // Start of file reached, out of bounds, so set EOF.
+    fseek(iptr, 0L, SEEK_END);
+}
diff --git a/comp1521/smips/input.h b/comp1521/smips/input.h
new file mode 100644
index 0000000..44ac0c9
--- /dev/null
+++ b/comp1521/smips/input.h
@@ -0,0 +1,12 @@
+#ifndef INPUT_H_
+#define INPUT_H_
+
+#include <ctype.h>
+#include <stdint.h>
+#include <stdio.h>
+
+uint32_t hex_to_decimal(const uint32_t decimal);
+uint32_t get_next_instruction(FILE *const iptr);
+void goto_previous_instruction(FILE *const iptr);
+
+#endif
diff --git a/comp1521/smips/instr.c b/comp1521/smips/instr.c
new file mode 100644
index 0000000..645fbae
--- /dev/null
+++ b/comp1521/smips/instr.c
@@ -0,0 +1,160 @@
+#include "instr.h"
+
+// Gets the immediate bits, clearing others and shifting right.
+uint32_t get_i(const uint32_t instr) { return instr & IMMEDIATE_BITS; }
+
+// Gets the pattern bits, clearing others and shifting right.
+uint32_t get_p(const uint32_t instr) { return (instr & PATTERN_BITS) >> 26; }
+
+// Gets the d bits, clearing others and shifting right.
+uint32_t get_d(const uint32_t instr) { return (instr & D_BITS) >> 11; }
+
+// Gets the t bits, clearing others and shifting right.
+uint32_t get_t(const uint32_t instr) { return (instr & T_BITS) >> 16; }
+
+// Gets the s bits, clearing others and shifting right.
+uint32_t get_s(const uint32_t instr) { return (instr & S_BITS) >> 21; }
+
+// $d = $s + $t.
+void mips_add(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] + registers[t];
+}
+
+// $d = $s - $t.
+void mips_sub(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] - registers[t];
+}
+// $d = $s & $t.
+void mips_and(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] & registers[t];
+}
+
+// $d = $s | $t.
+void mips_or(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] | registers[t];
+}
+
+// $d = ($s < $t).
+void mips_slt(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] < registers[t];
+}
+
+// $d = $s * $t.
+void mips_mul(const uint32_t instr, uint32_t registers[32]) {
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[d] = registers[s] * registers[t];
+}
+
+// If ($s == $t) PC += i.
+void mips_beq(FILE *const fptr, const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    if (registers[s] != registers[t]) {
+        return;
+    }
+    if (i >= 0) {
+        for (int j = 0; j <= i; ++j) {
+            get_next_instruction(fptr);
+        }
+    } else {
+        for (int j = 0; j <= -1 * i; ++j) {
+            goto_previous_instruction(fptr);
+        }
+    }
+}
+
+// If ($s != $t) PC += i.
+void mips_bne(FILE *const fptr, const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    if (registers[s] == registers[t]) {
+        return;
+    }
+    if (i >= 0) {
+        for (int j = 0; j <= i; ++j) {
+            get_next_instruction(fptr);
+        }
+    } else {
+        for (int j = 0; j <= -1 * i; ++j) {
+            goto_previous_instruction(fptr);
+        }
+    }
+}
+
+// $t = $s + i.
+void mips_addi(const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[t] = registers[s] + (uint32_t)i;
+}
+
+// $t = $s < i.
+void mips_slti(const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[t] = registers[s] < (uint32_t)i;
+}
+
+// $t = $s & i.
+void mips_andi(const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[t] = registers[s] & (uint32_t)i;
+}
+
+// $t = $s | i.
+void mips_ori(const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    registers[t] = registers[s] | (uint32_t)i;
+}
+
+// $t = i << 16u.
+void mips_lui(const uint32_t instr, uint32_t registers[32]) {
+    int i = (int16_t)get_i(instr);
+    int t = (int16_t)get_t(instr);
+    registers[t] = (uint32_t)i << 16u;
+}
+
+// Syscall function which returns non-zero if execution should stop.
+int mips_syscall(uint32_t registers[32]) {
+    uint32_t v0 = registers[2];
+    uint32_t a0 = registers[4];
+    switch (v0) {
+    case 1:
+        printf("%u", a0);
+        break;
+    case 11:
+        printf("%c", a0 & 0xFFu);
+        break;
+    case 10:
+        return 1;
+    default:
+        printf("Unknown system call: %d\n", v0);
+        return 1;
+    }
+    return 0;
+}
diff --git a/comp1521/smips/instr.h b/comp1521/smips/instr.h
new file mode 100644
index 0000000..720d32f
--- /dev/null
+++ b/comp1521/smips/instr.h
@@ -0,0 +1,103 @@
+#ifndef INSTR_H_
+#define INSTR_H_
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "input.h"
+
+// We have to use bit masks to identify the instruction we are to perform.
+// Instructions are stored in a uint32_t, and inputted from hex.
+// The format of the bit masks vary between
+//
+// PPPPPP SSSSS TTTTT DDDDD IIIIIIIIIII
+//   6      5     5     5       11
+//
+// PPPPPP SSSSS TTTTT  IIIIIIIIIIIIIIII
+//   6      5     5         16
+//
+// P = pattern_mask
+// S = five bit register number
+// T = five bit register number
+// D = five bit register number
+// I = immediate mask (size can very between instructions)
+
+// Definitions for 32 bit instruction bits.
+#define PATTERN_BITS 0xFC000000    // 11111100000000000000000000000000
+#define IMMEDIATE_BITS 0xFFFF      // 00000000000000001111111111111111
+#define SHORT_IMMEDIATE_BITS 0x7FF // 00000000000000000000011111111111
+#define S_BITS 0x3e00000           // 00000011111000000000000000000000
+#define T_BITS 0x1f0000            // 00000000000111110000000000000000
+#define D_BITS 0xf800              // 00000000000000001111100000000000
+
+// Contains bit masks for instructions for the immediate field.
+enum immediate_mask {
+    im_add = 0x20u,   // 100000
+    im_sub = 0x22u,   // 100010
+    im_and = 0x24u,   // 100100
+    im_or = 0x25u,    // 100101
+    im_slt = 0x2au,   // 101010
+    im_mul = 0x2u,    // 000010
+    im_syscall = 0xcu // 001100
+};
+
+// Contains bit masks for the pattern field.
+enum pattern_mask {
+    pm_add = 0x0u,  // 000000
+    pm_sub = 0x0u,  // 000000
+    pm_and = 0x0u,  // 000000
+    pm_or = 0x0u,   // 000000
+    pm_slt = 0x0u,  // 000000
+    pm_mul = 0x1cu, // 011100
+    pm_beq = 0x4u,  // 000100
+    pm_bne = 0x5u,  // 000101
+    pm_addi = 0x8u, // 001000
+    pm_slti = 0xau, // 001010
+    pm_andi = 0xcu, // 001100
+    pm_ori = 0xdu,  // 001101
+    pm_lui = 0xfu,  // 001111
+};
+
+// Contains an enum representing instructions.
+enum instructions {
+    add,
+    sub,
+    and,
+    or,
+    slt,
+    mul,
+    beq,
+    bne,
+    addi,
+    slti,
+    andi,
+    ori,
+    lui,
+    syscall
+};
+
+// Functions which extract bitfields from an instruction.
+uint32_t get_i(const uint32_t instr);
+uint32_t get_p(const uint32_t instr);
+uint32_t get_d(const uint32_t instr);
+uint32_t get_t(const uint32_t instr);
+uint32_t get_s(const uint32_t instr);
+
+// Functions which emulate mips instructions.
+void mips_add(const uint32_t instr, uint32_t registers[32]);
+void mips_sub(const uint32_t instr, uint32_t registers[32]);
+void mips_and(const uint32_t instr, uint32_t registers[32]);
+void mips_or(const uint32_t instr, uint32_t registers[32]);
+void mips_slt(const uint32_t instr, uint32_t registers[32]);
+void mips_mul(const uint32_t instr, uint32_t registers[32]);
+void mips_beq(FILE *const fptr, const uint32_t instr, uint32_t registers[32]);
+void mips_bne(FILE *const fptr, const uint32_t instr, uint32_t registers[32]);
+void mips_addi(const uint32_t instr, uint32_t registers[32]);
+void mips_slti(const uint32_t instr, uint32_t registers[32]);
+void mips_andi(const uint32_t instr, uint32_t registers[32]);
+void mips_ori(const uint32_t instr, uint32_t registers[32]);
+void mips_lui(const uint32_t instr, uint32_t registers[32]);
+int mips_syscall(uint32_t registers[32]);
+
+#endif
diff --git a/comp1521/smips/smips.c b/comp1521/smips/smips.c
new file mode 100644
index 0000000..19acd73
--- /dev/null
+++ b/comp1521/smips/smips.c
@@ -0,0 +1,243 @@
+// July 2020.
+// Simple mips emulator which only reads hex instructions.
+
+#include "smips.h"
+
+// Prints an instruction and its variables based off a supplied type.
+static void print_wrapper(const uint32_t instr, const char *name, const int type) {
+    int i = (int16_t)get_i(instr);
+    int d = (int16_t)get_d(instr);
+    int t = (int16_t)get_t(instr);
+    int s = (int16_t)get_s(instr);
+    switch (type) {
+    case DST:
+        printf("%-4s $%d, $%d, $%d", name, d, s, t);
+        break;
+    case STI:
+        printf("%-4s $%d, $%d, %d", name, s, t, i);
+        break;
+    case TSI:
+        printf("%-4s $%d, $%d, %d", name, t, s, i);
+        break;
+    case TI:
+        printf("%-4s $%d, %d", name, t, i);
+        break;
+    }
+}
+
+// Returns the instruction type as defined in the instr enum.
+// Returns >= 0 if the instruction was found.
+static int query_instruction(const uint32_t instr) {
+    uint32_t pattern = get_p(instr);
+    uint32_t immediate = get_i(instr);
+
+    // Syscall, mul and lui are special cases which should be dealt with before
+    // we move into the switch statatement.
+    if (pattern == pm_mul && (immediate & SHORT_IMMEDIATE_BITS) == im_mul) {
+        return mul;
+    } else if (instr == im_syscall) {
+        return syscall;
+    } else if (get_p(instr) == pm_lui && get_s(instr) == 0) {
+        return lui;
+    }
+
+    // If the pattern bits are empty, we are dealing with instructions between
+    // add and slt inclusive. This is only true after the special cases of mul,
+    // syscall and lui are dealt with. The others can be encapsulated in an
+    // else.
+    if (!pattern) {
+        switch (immediate & SHORT_IMMEDIATE_BITS) {
+        case im_add:
+            return add;
+        case im_sub:
+            return sub;
+        case im_and:
+            return and;
+        case im_or:
+            return or ;
+        case im_slt:
+            return slt;
+        default:
+            return -1;
+        }
+    } else {
+        switch (pattern) {
+        case pm_beq:
+            return beq;
+        case pm_bne:
+            return bne;
+        case pm_addi:
+            return addi;
+        case pm_slti:
+            return slti;
+        case pm_andi:
+            return andi;
+        case pm_ori:
+            return ori;
+        default:
+            return -1;
+        }
+    }
+    return 0;
+}
+
+// Calls print wrapper with the correct name char *.
+static void print_instruction(const uint32_t instr) {
+    switch (query_instruction(instr)) {
+    case mul:
+        print_wrapper(instr, "mul", DST);
+        break;
+    case lui:
+        print_wrapper(instr, "lui", TI);
+        break;
+    case syscall:
+        printf("syscall");
+        break;
+    case add:
+        print_wrapper(instr, "add", DST);
+        break;
+    case sub:
+        print_wrapper(instr, "sub", DST);
+        break;
+    case and:
+        print_wrapper(instr, "and", DST);
+        break;
+    case or:
+        print_wrapper(instr, "or", DST);
+        break;
+    case slt:
+        print_wrapper(instr, "slt", DST);
+        break;
+    case beq:
+        print_wrapper(instr, "beq", STI);
+        break;
+    case bne:
+        print_wrapper(instr, "bne", STI);
+        break;
+    case addi:
+        print_wrapper(instr, "addi", STI);
+        break;
+    case slti:
+        print_wrapper(instr, "slti", TSI);
+        break;
+    case andi:
+        print_wrapper(instr, "andi", TSI);
+        break;
+    case ori:
+        print_wrapper(instr, "ori", TSI);
+        break;
+    }
+}
+
+// Executes a mips_? function based off the enum returned from the
+// query_instruction function. Non-zero values indicates execution should stop.
+static int execute_instruction(FILE *const iptr, const uint32_t instr,
+                               uint32_t registers[32]) {
+    // At this point, guaranteed to be known instructions.
+    switch (query_instruction(instr)) {
+    case add:
+        mips_add(instr, registers);
+        break;
+    case sub:
+        mips_sub(instr, registers);
+        break;
+    case and:
+        mips_and(instr, registers);
+        break;
+    case or:
+        mips_or(instr, registers);
+        break;
+    case slt:
+        mips_slt(instr, registers);
+        break;
+    case mul:
+        mips_mul(instr, registers);
+        break;
+    case beq:
+        mips_beq(iptr, instr, registers);
+        break;
+    case bne:
+        mips_bne(iptr, instr, registers);
+        break;
+    case addi:
+        mips_addi(instr, registers);
+        break;
+    case slti:
+        mips_slti(instr, registers);
+        break;
+    case andi:
+        mips_andi(instr, registers);
+        break;
+    case ori:
+        mips_ori(instr, registers);
+        break;
+    case lui:
+        mips_lui(instr, registers);
+        break;
+    case syscall:
+        return mips_syscall(registers);
+        break;
+    }
+    // We need to restore $0, which should always be zero. So after each
+    // instruction, simply set it back to 0. Syscalls do not touch $0!
+    registers[0] = 0;
+    return 0;
+}
+
+int main(const int argc, const char *argv[]) {
+    if (argc < 2) {
+        printf("Not enough arguments!\n");
+        return EXIT_FAILURE;
+    }
+    FILE *iptr = fopen(argv[1], "r");
+    if (iptr == NULL) {
+        printf("File does not exist!\n");
+        return EXIT_FAILURE;
+    }
+    // We will read through program first, then perform a loop which
+    // reads out the instructions, loop which executes the instructions, then
+    // finally a loop which prints changed registers.
+    int i = 1;
+    uint32_t instr = 0;
+    while ((instr = get_next_instruction(iptr))) { // Proofread loop.
+        if (query_instruction(instr) == -1) {
+            printf("%s:%d: invalid instruction code: %08x\n", argv[1], i,
+                   instr);
+            return EXIT_FAILURE;
+        }
+        ++i;
+    }
+    rewind(iptr);
+
+    i = 0;
+    printf("Program\n");
+    while ((instr = get_next_instruction(iptr))) { // Print loop.
+        printf("%3d: ", i);
+        print_instruction(instr);
+        printf("\n");
+        ++i;
+    }
+    rewind(iptr);
+
+    uint32_t registers[32] = {0};
+    printf("Output\n");
+    while ((instr = get_next_instruction(iptr))) { // Execution loop.
+        // The iptr may change after execute_instruction runs due to branch
+        // instructions.
+        // In addition, execute instruction returns a non-zero if execution
+        // should stop due to syscalls, etc.
+        if (execute_instruction(iptr, instr, registers)) {
+            break;
+        }
+    }
+
+    printf("Registers After Execution\n"); // Print registers loop.
+    for (size_t j = 0; j < sizeof(registers) / sizeof(uint32_t); ++j) {
+        if (registers[j]) {
+            printf("$%-2d = %u\n", (int)j, registers[j]);
+        }
+    }
+
+    fclose(iptr);
+    return EXIT_SUCCESS;
+}
diff --git a/comp1521/smips/smips.h b/comp1521/smips/smips.h
new file mode 100644
index 0000000..94edf90
--- /dev/null
+++ b/comp1521/smips/smips.h
@@ -0,0 +1,20 @@
+#ifndef SMIPS_H_
+#define SMIPS_H_
+
+#include <ctype.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "input.h" // Contains functions for input and file processing.
+#include "instr.h" // Contains mips related instructions and bitmasks.
+
+// Definitions for printing multipliers (read print_wrapper).
+#define DST 1
+#define STI 2
+#define TSI 3
+#define TI 4
+#define SYSCALL 5
+
+#endif