diff --git a/src/Constants.js b/src/Constants.js
index b4307cca3..8d713fbe4 100644
--- a/src/Constants.js
+++ b/src/Constants.js
@@ -54,9 +54,12 @@ CONSTANTS = {
     ScriptScpRamCost:               0.5,
     ScriptHasRootAccessRamCost:     0.05,
     ScriptGetHostnameRamCost:       0.1,
-    ScriptGetHackingLevelRamCost:   0.1,
+    ScriptGetHackingLevelRamCost:   0.05,
     ScriptGetServerMoneyRamCost:    0.1,
-    ScriptGetServerSecurityRamCost: 0.2,
+    ScriptGetServerSecurityRamCost: 0.1,
+    ScriptGetServerReqdHackRamCost: 0.1,
+    ScriptFileExistsRamCost:        0.1,
+    ScriptIsRunningRamCost:         0.1,
     ScriptOperatorRamCost:          0.01,
     ScriptPurchaseHacknetRamCost:   1.5,
     ScriptHacknetNodesRamCost:      1.0, //Base cost for accessing hacknet nodes array
@@ -349,11 +352,19 @@ CONSTANTS = {
                            "The first argument must be a string with the name of the file. A file can either be a script or a program. A script name is case-sensitive, but a " +
                            "program is not. For example, fileExists('brutessh.exe') will work fine, even though the actual program is named BruteSSH.exe. <br><br> " + 
                            "The second argument is a string with the hostname or IP of the server on which to search for the program. This second argument is optional. " + 
-                           "If it is not specified, then the function will search through the current server for the file. <br> " + 
+                           "If it is omitted, then the function will search through the current server (the server running the script that calls this function) for the file. <br> " + 
                            "Example: fileExists('foo.script', 'foodnstuff');<br>" + 
                            "Example: fileExists('ftpcrack.exe');<br><br>" + 
                            "The first example above will return true if the script named 'foo.script' exists on the 'foodnstuff' server, and false otherwise. The second example above will " +
-                           "return true if the current server (the server on which the script is running) contains the FTPCrack.exe program, and false otherwise. <br><br>" + 
+                           "return true if the current server (the server on which this function runs) contains the FTPCrack.exe program, and false otherwise. <br><br>" + 
+                           "<i>isRunning(filename, [hostname/ip])</i><br> Returns a boolean (true or false) indicating whether the specified script is running on a server. " + 
+                           "The first argument must be a string with the name of the script. The script name is case sensitive. The second argument is a string with the " +
+                           "hostname or IP of the target server. The function will check whether the script is running on that target server. The second argument is optional. " + 
+                           "If it is omitted, then the function will check if the script is running on the current server (the server running the script that calls this function). <br>" + 
+                           "Example: isRunning('foo.script', 'foodnstuff');<br>" + 
+                           "Example: isRunning('foo.script'); <br><br>" + 
+                           "The first example above will return true if there is a script called 'foo.script' is running on the 'foodnstuff' server, and false otherwise. The second " + 
+                           "example above will return true if there is a script called 'foo.script' running on the current server, and false otherwise. <br><br>" + 
                            "<i>purchaseHacknetNode()</i><br> Purchases a new Hacknet Node. Returns a number with the index of the Hacknet Node. This index is equivalent to the number " + 
                            "at the end of the Hacknet Node's name (e.g The Hacknet Node named 'hacknet-node-4' will have an index of 4). If the player cannot afford to purchase " +
                            "a new Hacknet Node then the function will return false. Does NOT work offline<br><br>" + 
diff --git a/src/NetscriptEvaluator.js b/src/NetscriptEvaluator.js
index 7d40e3ebf..2100db5cc 100644
--- a/src/NetscriptEvaluator.js
+++ b/src/NetscriptEvaluator.js
@@ -123,9 +123,9 @@ function evaluate(exp, workerScript) {
                     var sleepTimePromise = evaluate(exp.args[0], workerScript);
                     sleepTimePromise.then(function(sleepTime) {
                         workerScript.scriptRef.log("Sleeping for " + sleepTime + " milliseconds");
-                        setTimeout(function() {
+                        return netscriptDelay(sleepTime).then(function() {
                             return Promise.resolve(true);
-                        }, sleepTime);
+                        });
                     }).then(function(res) {
                         resolve(true);
                     }).catch(function(e) {
@@ -412,7 +412,41 @@ function evaluate(exp, workerScript) {
                         if (Player.hasProgram(filename)) {
                             return resolve(true);
                         }
-                        return reject(false);
+                        return resolve(false);
+                    }).catch(function(e) {
+                        reject(e);
+                    });
+                } else if (exp.func.value == "isRunning") {
+                    if (exp.args.length != 1 && exp.args.length != 2) {
+                        return reject(makeRuntimeRejectMsg(workerScript, "isRunning() call has incorrect number of arguments. Takes 1 or 2 arguments")); 
+                    }
+                    var argPromises = exp.args.map(function(arg) {
+                        return evaluate(arg, workerScript);
+                    });
+                    
+                    var filename = "";
+                    Promise.all(argPromises).then(function(args) {
+                        if (env.stopFlag) {return reject(workerScript);}
+                        filename = args[0];
+                        if (exp.args.length == 2) {
+                            return Promise.resolve(workerScript.serverIp);
+                        } else {
+                            return evaluate(exp.args[1], workerScript);
+                        }
+                    }).then(function(ip) {
+                        var server = getServer(ip);
+                        if (server == null) {
+                            workerScript.scriptRef.log("isRunning() failed. Invalid IP or hostname passed in: " + ip);
+                            return reject(makeRuntimeRejectMsg(workerScript, "Invalid IP or hostname passed into isRunning() command"));
+                        }
+                        
+                        for (var i = 0; i < server.runningScripts.length; ++i) {
+                            if (filename == server.runningScripts[i]) {
+                                return resolve(true);
+                            }
+                        }
+                        
+                        return resolve(false);
                     }).catch(function(e) {
                         reject(e);
                     });
diff --git a/src/Script.js b/src/Script.js
index eb96aae70..84c785732 100644
--- a/src/Script.js
+++ b/src/Script.js
@@ -228,6 +228,9 @@ Script.prototype.updateRamUsage = function() {
     var getHackingLevelCount = numOccurrences(codeCopy, "getHackingLevel(");
     var getServerMoneyAvailableCount = numOccurrences(codeCopy, "getServerMoneyAvailable(");
     var getServerSecurityCount = numOccurrences(codeCopy, "getServerSecurityLevel(");
+    var getServerReqdHackingCount = numOccurrences(codeCopy, "getServerRequiredHackingLevel(");
+    var fileExistsCount = numOccurrences(codeCopy, "fileExists(");
+    var isRunningCount = numOccurrences(codeCopy, "isRunning(");
     var numOperators = numNetscriptOperators(codeCopy);
     var purchaseHacknetCount = numOccurrences(codeCopy, "purchaseHacknetNode(");
     var hacknetnodesArrayCount = numOccurrences(codeCopy, "hacknetnodes[");
@@ -256,6 +259,9 @@ Script.prototype.updateRamUsage = function() {
                     (getHackingLevelCount * CONSTANTS.ScriptGetHackingLevelRamCost) + 
                     (getServerMoneyAvailableCount * CONSTANTS.ScriptGetServerMoneyRamCost) + 
                     (getServerSecurityCount * CONSTANTS.ScriptGetServerSecurityRamCost) +
+                    (getServerReqdHackingCount * CONSTANTS.ScriptGetServerReqdHackRamCost) + 
+                    (fileExistsCount * CONSTANTS.ScriptFileExistsRamCost) + 
+                    (isRunningCount * CONSTANTS.ScriptIsRunningRamCost) +
                     (numOperators * CONSTANTS.ScriptOperatorRamCost) +
                     (purchaseHacknetCount * CONSTANTS.ScriptPurchaseHacknetRamCost) + 
                     (hacknetnodesArrayCount * CONSTANTS.ScriptHacknetNodesRamCost) +