update prelab

Labs/Lab3/Makefile

+CC = gcc
+CFLAGS = -std=gnu99 -Wall -g #-DDEBUG
+LFLAGS = -lpthread -lm
+
+EXECS = pthread_hello time_demo mergesort
+
+all: EXECS
+warppers.o: wrappers.h wrappers.c
+	$(CC) $(CFLAGS) -c wrappers.c wrappers.h -o wrappers.o
+
+char-threads: char-threads.c wrappers.o
+	$(CC) $(CFLAGS) -o $@ $< wrappers.o $(LFLAGS) 
+
+mytime: mytime.c
+	$(CC) $(CFLAGS) -o $@ $< $(LFLAGS) 
+
+summation: summation.c
+
+	$(CC) $(CFLAGS) -o $@ $< $(LFLAGS) 
+
+.PHONY: clean
+clean:
+	/bin/rm -f *.o $(EXECS)
+

Labs/Lab3/char-threads.c

@@ -2,15 +2,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #define NUM_THREADS 3
-
-int PthreadCreate(pthread_t *thread, const pthread_attr_t *attr,void *(*start_routine) (void *), void *arg) {
-	int RET;
-	if (RET = pthread_create(thread, attr, start_routine, arg)) {
-	perror("Thread failed");
-	exit(-1);
-     }
-     return RET;
-};
+#include "wrappers.h"
 
 void *PrintChar(void *threadid) {
 	long TID;
@@ -47,12 +39,11 @@ void *PrintChar(void *threadid) {
 
 int main (int argc, char *argv[]) {
     pthread_t threads[NUM_THREADS];
-	int RC;
 	long T;
 
-    for(T=0; t<NUM_THREADS; T++){
-	   printf("In main: creating thread %ld\n", T);
-       PthreadCreate(&threads[t], NULL, PrintChar, (void *)T);
+    for(T=0; T<NUM_THREADS; T++){
+	   printf("The thread %ld has been created\n", T);
+       PthreadCreate(&threads[T], NULL, PrintChar, (void *)T);
     }
 
 	pthread_exit(NULL);

Labs/Lab3/mytime.c

@@ -3,10 +3,11 @@
 #include <time.h>
 
 int main (int argc, char *argv[]) {
-	struct timeval struct_time;
-	gettimeofday(&struct_time, NULL);
+	struct timeval struct_time; //to make a timeval type object "struct_time"
+ 				    //bc a pointer to this type of struct is required by the gettimeofday()function
+	gettimeofday(&struct_time, NULL); //gettimeof day will store a time_c type into "struct_time"
 
-	char *CTIMESTR = ctime(&struct_time.tv_sec);
-	printf("Ctime String: %s", CTIMESTR;
+	char *CTIMESTR = ctime(&struct_time.tv_sec);//ctime converts time_t type to a string.
+	printf("Ctime String: %s", CTIMESTR);
 }