prelab complete

Labs/Lab07/exit.s

+#exit.s
+	.text
+	.global _start
+_start:
+	li a0, 42
+	li a7, 93
+	ecall

Labs/Lab07/primes.c

+/*
+real:19.823s
+user:19.508s
+sys:0.308s
+ */
+#include <stdio.h> 
+#include <stdlib.h>
+int is_prime(int n)
+{
+    int i;
+    for (i = 2; i < (n-1); i++){
+        if ((n%i) == 0){
+            return 0;
+        }   
+    }
+    return 1;
+}
+
+
+int main (int argc, char* argv[])
+{
+    int i, n = 0, maxnum=80;
+    if (argc > 1){
+        maxnum = atoi(argv[1]);
+    }
+	
+    for (i = 2; n < maxnum; i++){
+        if (is_prime(i)){
+            printf("%7d", i);
+            n++;
+            if ((n % 10) == 0){
+                printf("\n");
+            }
+        }
+    }
+
+    return 0;
+}