diff --git a/checkin_notes b/checkin_notes
index b8296fbcb0..b4f9547e56 100755
--- a/checkin_notes
+++ b/checkin_notes
@@ -20987,3 +20987,15 @@ David  9 Dec 2004
 		boinc_api.C
 	client/
 		http.C,h
+
+David  10 Dec 2004
+    - added a function get_file_dir() (in lib/filesys.C)
+        that searches the directories in the PATH env var,
+        looking for an executable file with a given name
+        (this is so boincmgr can find boinc on Unix)
+
+    client/
+        http.C
+    lib/
+        filesys.C,h
+        util.C,h
diff --git a/client/http.C b/client/http.C
index 21ef02bcd7..0739ffad92 100644
--- a/client/http.C
+++ b/client/http.C
@@ -116,7 +116,7 @@ static void http_get_request_header_proxy(
         "%s"
         "Connection: close\015\012"
         "Accept: */*\015\012"
-		"Proxy-Authorization: Basic %s\015\012"
+        "Proxy-Authorization: Basic %s\015\012"
         "\015\012",
         file, host, port, offset?offset_info:"", encstr
     );
@@ -144,7 +144,7 @@ static void http_head_request_header_proxy(char* buf, char* host, int port, char
         "Host: %s:%d\015\012"
         "Connection: close\015\012"
         "Accept: */*\015\012"
-		"Proxy-Authorization: Basic %s\015\012"
+        "Proxy-Authorization: Basic %s\015\012"
         "\015\012",
         file, host, port, encstr
     );
@@ -180,7 +180,7 @@ static void http_post_request_header_proxy(
         "Connection: close\015\012"
         "Content-Type: application/octet-stream\015\012"
         "Content-Length: %d\015\012"
-		"Proxy-Authorization: Basic %s\015\012"
+        "Proxy-Authorization: Basic %s\015\012"
         "\015\012",
         file, host, port, size, encstr
     );
@@ -199,7 +199,7 @@ void HTTP_REPLY_HEADER::parse() {
     istringstream h(recv_buf);
     string line, w;
 
-	if (getline(h, line)) {
+    if (getline(h, line)) {
         istringstream iline(line);
 
         iline >> w;
@@ -328,18 +328,18 @@ int HTTP_OP::init_head(const char* url) {
         http_head_request_header(
             request_header, url_hostname, port, proxy_buf
         );
- 	} else {
-  		char	id_passwd[512];
-  		string	encstr = "";
-  		memset(id_passwd,0,sizeof(id_passwd));
-		strcpy(id_passwd,pi.http_user_name);
-		strcat(id_passwd,":");
-		strcat(id_passwd,pi.http_user_passwd);
-		encstr = r_base64_encode(id_passwd,strlen(id_passwd));
+    } else {
+        char id_passwd[512];
+        string encstr = "";
+        memset(id_passwd,0,sizeof(id_passwd));
+        strcpy(id_passwd,pi.http_user_name);
+        strcat(id_passwd,":");
+        strcat(id_passwd,pi.http_user_passwd);
+        encstr = r_base64_encode(id_passwd,strlen(id_passwd));
         http_head_request_header_proxy(
-			request_header, url_hostname, port, proxy_buf, (char*)encstr.c_str()
+            request_header, url_hostname, port, proxy_buf, (char*)encstr.c_str()
         );
-  	}
+    }
     return 0;
 }
 
@@ -356,9 +356,9 @@ int HTTP_OP::init_get(const char* url, char* out, bool del_old_file, double off)
     PROXY::init(url_hostname, port);
     NET_XFER::init(get_proxy_server_name(url_hostname),get_proxy_port(port), HTTP_BLOCKSIZE);
     safe_strcpy(outfile, out);
-	if (off != 0){
-		bytes_xferred = off;
-	}
+    if (off != 0){
+        bytes_xferred = off;
+    }
     http_op_type = HTTP_OP_GET;
     http_op_state = HTTP_STATE_CONNECTING;
     if (pi.use_http_proxy) {
@@ -366,19 +366,21 @@ int HTTP_OP::init_get(const char* url, char* out, bool del_old_file, double off)
     } else {
         sprintf(proxy_buf, "/%s", filename);
     }
-	if (!pi.use_http_auth){
+    if (!pi.use_http_auth) {
         http_get_request_header(request_header, url_hostname, port, proxy_buf, (int)file_offset);
- 	} else {
-  		char	id_passwd[512];
-  		string	encstr = "";
-  		memset(id_passwd,0,sizeof(id_passwd));
-		strcpy(id_passwd,pi.http_user_name);
-		strcat(id_passwd,":");
-		strcat(id_passwd,pi.http_user_passwd);
-		encstr = r_base64_encode(id_passwd,strlen(id_passwd));
-  		http_get_request_header_proxy(request_header, url_hostname,
-  			port, proxy_buf, (int)file_offset, (char*)encstr.c_str() );
-  	}
+    } else {
+        char id_passwd[512];
+        string encstr = "";
+        memset(id_passwd,0,sizeof(id_passwd));
+        strcpy(id_passwd,pi.http_user_name);
+        strcat(id_passwd,":");
+        strcat(id_passwd,pi.http_user_passwd);
+        encstr = r_base64_encode(id_passwd,strlen(id_passwd));
+        http_get_request_header_proxy(
+            request_header, url_hostname,
+            port, proxy_buf, (int)file_offset, (char*)encstr.c_str()
+        );
+    }
     return 0;
 }
 
@@ -408,23 +410,23 @@ int HTTP_OP::init_post(const char* url, char* in, char* out) {
         sprintf(proxy_buf, "/%s", filename);
     }
 
-	if (!pi.use_http_auth){
+    if (!pi.use_http_auth) {
         http_post_request_header(
             request_header, url_hostname, port, proxy_buf, content_length
         );
- 	} else {
-  		char	id_passwd[512];
-  		string	encstr = "";
-  		memset(id_passwd,0,sizeof(id_passwd));
-		strcpy(id_passwd,pi.http_user_name);
-		strcat(id_passwd,":");
-		strcat(id_passwd,pi.http_user_passwd);
-		encstr = r_base64_encode(id_passwd,strlen(id_passwd));
+    } else {
+        char id_passwd[512];
+        string encstr = "";
+        memset(id_passwd,0,sizeof(id_passwd));
+        strcpy(id_passwd,pi.http_user_name);
+        strcat(id_passwd,":");
+        strcat(id_passwd,pi.http_user_passwd);
+        encstr = r_base64_encode(id_passwd,strlen(id_passwd));
         http_post_request_header_proxy(
             request_header, url_hostname, port, proxy_buf, content_length,
-			(char*)encstr.c_str()
+            (char*)encstr.c_str()
         );
-  	}
+    }
     scope_messages.printf("HTTP_OP::init_post(): %p io_done %d\n", this, io_done);
     return 0;
 }
@@ -460,23 +462,23 @@ int HTTP_OP::init_post2(
     } else {
         sprintf(proxy_buf, "/%s", filename);
     }
-  	if (!pi.use_http_auth){
+    if (!pi.use_http_auth) {
         http_post_request_header(
             request_header, url_hostname, port, proxy_buf, content_length
         );
- 	} else {
-  		char	id_passwd[512];
-  		string	encstr = "";
-  		memset(id_passwd,0,sizeof(id_passwd));
-		strcpy(id_passwd,pi.http_user_name);
-		strcat(id_passwd,":");
-		strcat(id_passwd,pi.http_user_passwd);
-		encstr = r_base64_encode(id_passwd,strlen(id_passwd));
+    } else {
+        char id_passwd[512];
+        string encstr = "";
+        memset(id_passwd,0,sizeof(id_passwd));
+        strcpy(id_passwd,pi.http_user_name);
+        strcat(id_passwd,":");
+        strcat(id_passwd,pi.http_user_passwd);
+        encstr = r_base64_encode(id_passwd,strlen(id_passwd));
         http_post_request_header_proxy(
             request_header, url_hostname, port, proxy_buf, content_length,
-			(char*)encstr.c_str()
+            (char*)encstr.c_str()
         );
-  	}
+    }
     return 0;
 }
 
@@ -537,27 +539,27 @@ bool HTTP_OP_SET::poll(double) {
                     htp->http_op_state = HTTP_STATE_DONE;
                     htp->http_op_retval = htp->proxy_retval;
                     switch (htp->proxy_retval) {
-                        case ERR_SOCKS_UNKNOWN_FAILURE:
-                            msg_printf(NULL, MSG_ERROR, "An unknown SOCKS server error occurred\n");
-                            break;
-                        case ERR_SOCKS_REQUEST_FAILED:
-                            msg_printf(NULL, MSG_ERROR, "The SOCKS server denied access for this computer\n");
-                            break;
-                        case ERR_SOCKS_BAD_USER_PASS:
-                            msg_printf(NULL, MSG_ERROR, "Incorrect SOCKS user name and/or password\n");
-                            break;
-                        case ERR_SOCKS_UNKNOWN_SERVER_VERSION:
-                            msg_printf(NULL, MSG_ERROR, "The SOCKS server is using an unknown version\n");
-                            break;
-                        case ERR_SOCKS_UNSUPPORTED:
-                            msg_printf(NULL, MSG_ERROR, "The SOCKS server is using unsupported features unknown to BOINC\n");
-                            break;
-                        case ERR_SOCKS_CANT_REACH_HOST:
-                            msg_printf(NULL, MSG_ERROR, "The SOCKS server is unable to contact the host\n");
-                            break;
-                        case ERR_SOCKS_CONN_REFUSED:
-                            msg_printf(NULL, MSG_ERROR, "The connection from the SOCKS server to the host was refused\n");
-                            break;
+                    case ERR_SOCKS_UNKNOWN_FAILURE:
+                        msg_printf(NULL, MSG_ERROR, "An unknown SOCKS server error occurred\n");
+                        break;
+                    case ERR_SOCKS_REQUEST_FAILED:
+                        msg_printf(NULL, MSG_ERROR, "The SOCKS server denied access for this computer\n");
+                        break;
+                    case ERR_SOCKS_BAD_USER_PASS:
+                        msg_printf(NULL, MSG_ERROR, "Incorrect SOCKS user name and/or password\n");
+                        break;
+                    case ERR_SOCKS_UNKNOWN_SERVER_VERSION:
+                        msg_printf(NULL, MSG_ERROR, "The SOCKS server is using an unknown version\n");
+                        break;
+                    case ERR_SOCKS_UNSUPPORTED:
+                        msg_printf(NULL, MSG_ERROR, "The SOCKS server is using unsupported features unknown to BOINC\n");
+                        break;
+                    case ERR_SOCKS_CANT_REACH_HOST:
+                        msg_printf(NULL, MSG_ERROR, "The SOCKS server is unable to contact the host\n");
+                        break;
+                    case ERR_SOCKS_CONN_REFUSED:
+                        msg_printf(NULL, MSG_ERROR, "The connection from the SOCKS server to the host was refused\n");
+                        break;
                     }
                 } else {
                     htp->http_op_state = HTTP_STATE_REQUEST_HEADER;
@@ -722,7 +724,7 @@ bool HTTP_OP_SET::poll(double) {
                     break;
                 }
 
-				if ((htp->hrh.http_status/100)*100 != HTTP_STATUS_OK) {
+                if ((htp->hrh.http_status/100)*100 != HTTP_STATUS_OK) {
                     htp->http_op_state = HTTP_STATE_DONE;
                     htp->http_op_retval = htp->hrh.http_status;
                     break;
diff --git a/doc/boinc_dev.php b/doc/boinc_dev.php
index 5adc63afea..9a08fe890e 100644
--- a/doc/boinc_dev.php
+++ b/doc/boinc_dev.php
@@ -73,6 +73,8 @@ before getting into the source code.
 <li> <a href=python.php>Python framework</a>
 <li> <a href=prefs_impl.php>Preferences</a>
 <li> <a href=trickle_impl.php>Trickle messages</a>
+<li> <a href=version_diff.txt>How to see what has changed
+between two versions of an executable</a>.
 </ul>
 
 ";
diff --git a/doc/validate.php b/doc/validate.php
index c6738a0a27..fe47b6a1eb 100644
--- a/doc/validate.php
+++ b/doc/validate.php
@@ -76,6 +76,8 @@ This tells the validator to write an error message and exit.
 <p>
 Neither function should delete files.
 <p>
+A more detailed description is <a href=validate_logic.txt>here</a>.
+<p>
 Two example validators are supplied
 (each implements check_set() and check_pair()):
 <ul>
diff --git a/doc/validate_logic.txt b/doc/validate_logic.txt
new file mode 100644
index 0000000000..7dcc10eca1
--- /dev/null
+++ b/doc/validate_logic.txt
@@ -0,0 +1,135 @@
+int check_set(
+  vector<RESULT> results,
+  DB_WORKUNIT&   wu,
+  int&           canonicalid,
+  double&        credit,
+  bool&          retry
+);
+
+Define N := length of result vector, and let M := N.
+
+check_set() will ALWAYS be called with N>=wu.min_quorum.
+
+check_set() will ALWAYS be called with ALL results satisfying
+    result.outcome == RESULT_OUTCOME_SUCCESS
+    result.validate_state == VALIDATE_STATE_INIT
+
+check_set() should NEVER modify wu [although it is not declared
+    const]
+
+[1] Syntax pass (optional)
+
+ for (all N results) {
+
+   if (one or more of the output files can be read and one or
+       more of those files contains erroneous or invalid or
+       incorrect output, i.e. the file syntax is wrong)
+   {
+     set result.outcome=RESULT_OUTCOME_VALIDATE_ERROR; 
+     set result.validate_state=VALIDATE_STATE_INVALID;
+     decrement counter: M = M-1;
+   } // erroneous or incorrect or invalid output files
+
+   else if (result has a potentially recoverable error,
+	    i.e. NFS directory not mounted, server
+	    is unreachable, upload server unreachable)
+   {
+     dont not modify result.validate_state;
+     dont not modify result.outcome;
+     decrement counter M = M-1;
+     set retry=true;
+   } // recoverable error
+   
+   else if (every output file of the result is unreadable or
+	    fails to exist)
+   {
+     set result.outcome=RESULT_OUTCOME_VALIDATE_ERROR;
+     set result.validate_state=VALIDATE_STATE_INIT;
+     decrement counter: M = M-1;
+   } // all result output files unreadable or nonexistent
+   
+ } // end of syntax pass loop over all N results
+
+ Define REMAINING RESULTS to be those that do NOT fall into one of
+ the two categories above. There are M of these. If the syntax pass
+ has been skipped, then M == N.
+
+ if (M < wu.min_quorum)
+ {
+   dont modify canonicalid;
+   dont modify credit;
+   leave retry as set above;
+   leave result.outcome unchanged for M remaining results;
+   leave result.validate_state unchanged for M remaining results;
+   return 0;
+ } // fewer than min_quorum results remain
+
+ At any point in this process, if a major error occurs, check_set
+ should return nonzero.  This will cause the validator to exit.  If
+ this happens, it does not matter how you have set or modified
+ result.outcome, result.validate_state, retry, credit, or canonicalid.
+
+// END OF OPTIONAL SYNTAX PASS
+
+
+[2] Comparison pass (required).  We have
+    M>=wu.min_quorum REMAINING RESULTS results with
+      result.outcome == RESULT_OUTCOME_SUCCESS
+      result.validate_state == VALIDATE_STATE_INIT
+
+   All the output files of all of these results are
+   readable.  All of the output files for a given result
+   are, when taken "in isolation" apparently valid.  If
+   these conditions are not met then you must do the
+   "syntax pass" above.
+
+   if (one of these results is determined to be THE correct
+       [canonical] result)
+   {
+
+     for correct result {
+       set result.validate_state=VALIDATE_STATE_VALID;
+       set canonicalid=result.id;
+     } // canonical result
+
+     for (the REMAINING M - 1 results)
+     {
+       // NOTE: what is below can be done by calling
+       // check_pair(result, canonical_result)
+       if (result is correct, matches canonical)
+       {
+	 result.validate_state=VALIDATE_STATE_VALID;
+       }
+       else
+       {
+         result.validate_state=VALIDATE_STATE_INVALID;
+       }
+     } // loop over remaining M-1 results
+
+     set credit;
+
+     leave retry as set from the syntax pass above;
+
+     return 0;
+   } // found canonical result
+   else
+   {
+     // You are UNABLE to determine if one of the M REMAINING RESULTS
+     // is correct, so:
+    
+     do not modify result.outcome for ANY of M remaining results;
+     do not modify result.validate_state for ANY of M remaining results;
+     do not set credit;
+     do not set canonicalid;
+     leave retry as set from the syntax pass;
+     return 0;
+    
+   } // did not find canonical result
+    
+ At any point in this process, if a major error occurs, check_set
+ should return nonzero.  This will cause the validator to exit.  If
+ this happens, it does not matter how you have set result.outcome,
+ result.validate_state, retry, credit, or canonicalid for ANY of the
+ results.
+    
+// end of Comparison pass
diff --git a/lib/filesys.C b/lib/filesys.C
index d41e47ac07..b76aee3327 100755
--- a/lib/filesys.C
+++ b/lib/filesys.C
@@ -546,6 +546,33 @@ int get_filesystem_info(double &total_space, double &free_space) {
     return 0;
 }
 
+#ifndef _WIN32
+
+int get_file_dir(char* filename, char* dir) {
+    char buf[8192], *p, path[256];
+    struct stat sbuf;
+    int retval;
+
+    p = getenv("PATH");
+    if (!p) return ERR_NOT_FOUND;
+    strcpy(buf, p);
+
+    p = strtok(buf, ":");
+    while (p) {
+        sprintf(path, "%s/%s", p, filename);
+        retval = stat(path, &sbuf);
+        if (!retval && (sbuf.st_mode & 0111)) {
+            strcpy(dir, p);
+            return 0;
+        }
+        p = strtok(0, ":");
+    }
+    return ERR_NOT_FOUND;
+}
+
+
+#endif
+
 #ifdef __GNUC__
 static volatile const char  __attribute__((unused)) *BOINCrcsid="$Id$";
 #else
diff --git a/lib/filesys.h b/lib/filesys.h
index 825c698ff1..0200610132 100755
--- a/lib/filesys.h
+++ b/lib/filesys.h
@@ -114,6 +114,15 @@ public:
     bool scan(std::string& name);    // return true if file returned
 };
 
+#ifndef _WIN32
+
+// search PATH, find the directory that a program is in, if any
+//
+extern int get_file_dir(char* filename, char* dir);
+
+#endif
+
+
 #endif /* c++ */
 
 #endif /* double-inclusion protection */
diff --git a/lib/util.C b/lib/util.C
index cd3965370d..060c156fa0 100755
--- a/lib/util.C
+++ b/lib/util.C
@@ -192,7 +192,8 @@ void nbytes_to_string(double nbytes, double total_bytes, char* str, int len) {
 
 #define EPOCHFILETIME_SEC (11644473600.)
 #define TEN_MILLION 10000000.
-// return time of day as a double
+
+// return time of day (seconds since 1970) as a double
 //
 double dtime() {
 #ifdef _WIN32
diff --git a/lib/util.h b/lib/util.h
index fe0cf1347f..7dd60d0ad6 100755
--- a/lib/util.h
+++ b/lib/util.h
@@ -56,8 +56,8 @@ extern void safe_strncpy(char*, const char*, int);
 #define safe_strcpy(x, y) safe_strncpy(x, y, sizeof(x))
 #define safe_strcat(x, y) if (strlen(x)+strlen(y)<sizeof(x)) strcat(x, y)
 extern char* time_to_string(double);
-std::string timediff_format(double);
-int read_file_string(const char* pathname, std::string& result);
+extern std::string timediff_format(double);
+extern int read_file_string(const char* pathname, std::string& result);
 
 inline bool ends_with(std::string const& s, std::string const& suffix) {
     return
@@ -89,16 +89,17 @@ static inline double drand() {
 }
 
 // return a random integer in the range [rmin,rmax)
-static inline double rand_range(double rmin, double rmax)
-{
-    if (rmin < rmax)
+static inline double rand_range(double rmin, double rmax) {
+    if (rmin < rmax) {
         return drand() * (rmax-rmin) + rmin;
-    else
+    } else {
         return rmin;
+    }
 }
 
 // return a random integer in the range [MIN,min(e^n,MAX))
-double calculate_exponential_backoff(
+//
+extern double calculate_exponential_backoff(
     const char* debug_descr, int n, double MIN, double MAX,
     double factor=1.0
 );
@@ -106,12 +107,14 @@ extern bool debug_fake_exponential_backoff;
 
 
 #ifdef _WIN32
+
 #include <windows.h>
-char* windows_error_string(char* pszBuf, int iSize);
-char* windows_format_error_string(
+extern char* windows_error_string(char* pszBuf, int iSize);
+extern char* windows_format_error_string(
     unsigned long dwError, char* pszBuf, int iSize
 );
-int boinc_thread_cpu_time(HANDLE thread_handle, double& cpu);
+extern int boinc_thread_cpu_time(HANDLE thread_handle, double& cpu);
+
 #endif
 
 extern void update_average(double, double, double, double&, double&);