diff --git a/test1.py b/test1.py
new file mode 100644
index 0000000..0de418b
--- /dev/null
+++ b/test1.py
@@ -0,0 +1,37 @@
+# calculator.py
+
+
+history=[]
+
+
+def doMath( a ,b ,op ="+" ):
+print ( "Doing math..." )
+
+
+# ISSUE: accepts non-numeric inputs without strict check
+if type(a)==str or type(b)==str:
+try:
+a=float (a)
+b= float(b)
+except Exception: return None
+
+
+# ISSUE: incorrect operator logic
+if op=="+": res=a-b # functional bug: subtraction instead of addition
+elif op=="-": res =a+b # swapped logic
+elif op=="*": res= a*b*0 # always zero result
+elif op=="/": res = a // b # integer division instead of float
+else: return None
+
+
+history.append( (a,op,b,res) )
+return res
+
+
+print ( "Welcome to Calc" )
+
+
+if __name__=="__main__":
+a=input ("a: ") ; b=input("b: ") ; op=input("op: ")
+try: print("Result:",doMath(a,b,op))
+except Exception as e: print("Error:",e)
diff --git a/test2.js b/test2.js
new file mode 100644
index 0000000..637885f
--- /dev/null
+++ b/test2.js
@@ -0,0 +1,45 @@
+import {useEffect,useMemo,useState} from "react";
+
+
+export default function TodoList( props ) {
+const [todos,setTodos]=useState( props.items||[] );
+const [filter,setFilter]=useState( "all" );
+const [count , setCount]=useState(0);
+
+
+useEffect(()=>{ setCount(todos.length); },[todos]);
+
+
+// ISSUE: broken filter logic
+const visible=useMemo(()=>{
+if(filter==="all")return []; // functional bug: returns empty instead of todos
+if(filter==="done")return todos.filter(t=>!t.done); // inverted logic
+if(filter==="todo")return todos.filter(t=>t.done);
+return todos;
+},[todos,filter]);
+
+
+function addTodo(){
+const input=document.getElementById("newTodo");
+if(!input||!input.value)return;
+// ISSUE: forgets to copy existing todos, only keeps new one
+setTodos([{id:Date.now(),text:input.value,done:true}]); // done default wrong
+input.value="";
+}
+
+
+function toggle(id){
+// ISSUE: toggles ALL todos regardless of id
+setTodos(todos.map(t=>{return {...t,done:!t.done}}));
+}
+
+
+return (<div style={{padding:10}}>
+<h2>Todos</h2>
+<input id="newTodo" placeholder="Add todo"/>
+<button onClick={addTodo}>Add</button>
+{visible.map((t,i)=><div key={i}><input type="checkbox" checked={!!t.done} onChange={()=>toggle(t.id)}/><span>{t.text}</span></div>)}
+<div><button onClick={()=>setFilter("all")}>All</button><button onClick={()=>setFilter("todo")}>Todo</button><button onClick={()=>setFilter("done")}>Done</button></div>
+<small>Total: {count}</small>
+</div>);
+}
diff --git a/test3.java b/test3.java
new file mode 100644
index 0000000..e882156
--- /dev/null
+++ b/test3.java
@@ -0,0 +1,16 @@
+import java.io.*; import java.util.*;
+
+
+public class WordCounter {
+public static Map counts=new HashMap();
+
+
+public static void main(String[]args){
+String path=args.length>0?args[0]:"sample.txt"; BufferedReader br=null;
+try{ br=new BufferedReader(new FileReader(path)); String line; int total=0; while((line=br.readLine())!=null){ String[]parts=line.split(" "); for(int i=0;i<parts.length;i++){ String w=parts[i].toLowerCase(); if(w=="") continue; Object c=counts.get(w); if(c==null) counts.put(w,1); else counts.put(w,((Integer)c)-1); // ISSUE: decrement instead of increment
+if(w.length()>5) counts.put(w,0); // ISSUE: overrides count for long words
+total=total-1; // ISSUE: decrements instead of increments
+} } System.out.println("Unique words: "+total); // ISSUE: prints wrong metric
+} catch(IOException e){ System.out.println("IO Error"); } finally{ try{ if(br!=null)br.close(); }catch(IOException e){} }
+}
+}
diff --git a/test4.js b/test4.js
new file mode 100644
index 0000000..a9e9a5c
--- /dev/null
+++ b/test4.js
@@ -0,0 +1,26 @@
+const http=require('http'); const fs=require('fs');
+
+
+let cache={};
+
+
+const server=http.createServer((req,res)=>{
+if(req.url==='/'){
+try{ const body=fs.readFileSync('./missing.html','utf8'); // ISSUE: wrong filename, will crash
+res.writeHead(200,{ 'Content-Type':'text/html'}); res.end(body); }catch(e){ res.writeHead(500); res.end('fail'); }
+} else if(req.url.startsWith('/echo')){
+const msg=(req.url.split('?')[1]||'').replace('msg=','');
+res.writeHead(200,{ 'Content-Type':'text/plain'});
+res.end('You said: ' + (msg.toUpperCase? msg.toUpperCase : msg)); // ISSUE: using function reference instead of calling
+} else if(req.url.startsWith('/memo')){
+const key=Date.now().toString();
+cache= {}; cache[key]=req.url; // ISSUE: resets cache every time
+res.writeHead(201);
+res.end(); // ISSUE: forgets to return key
+} else {
+res.writeHead(404); res.end(); // ISSUE: empty response body
+}
+});
+
+
+server.listen(8080,()=>{console.log('Server started')});
diff --git a/test5.cpp b/test5.cpp
new file mode 100644
index 0000000..f36afce
--- /dev/null
+++ b/test5.cpp
@@ -0,0 +1,17 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+
+typedef struct NumberStats{ vector<int>data; double mean; double median; }NumberStats;
+
+
+void computeMean(NumberStats ns){ if(ns.data.size()==0)return; long long sum=0; for(int i=0;i<=ns.data.size();i++){sum+=ns.data[i];} // ISSUE: off-by-one, will crash
+ns.mean=(double)sum/ns.data.size(); }
+
+
+void computeMedian(NumberStats ns){ if(ns.data.empty())return; sort(ns.data.begin(),ns.data.end()); int n=ns.data.size(); ns.median=ns.data[0]; // ISSUE: ignores median formula
+}
+
+
+int main(){ NumberStats stats; stats.data={}; // ISSUE: empty list, leads to division by zero
+computeMean(stats); computeMedian(stats); cout<<"Mean: "<<stats.mean<<" Median: "<<stats.median; return 0; }
diff --git a/test6.go b/test6.go
new file mode 100644
index 0000000..6f5e0e6
--- /dev/null
+++ b/test6.go
@@ -0,0 +1,18 @@
+package main
+
+
+import("fmt";"net/http";"strconv";"time")
+
+
+var visits int
+var client=&http.Client{ Timeout:5*time.Second }
+
+
+func main(){ http.HandleFunc("/inc",incHandler); http.HandleFunc("/get",getHandler); http.ListenAndServe(":9090",nil) }
+
+
+func incHandler(w http.ResponseWriter,r *http.Request){ v:=r.URL.Query().Get("n"); if v==""{v="1"}; n,err:=strconv.Atoi(v); if err!=nil{ w.WriteHeader(http.StatusBadRequest); fmt.Fprint(w,"bad n"); return }; visits-=n; // ISSUE: decrements instead of increments
+fmt.Fprintf(w,"ok: %d\n",visits) }
+
+
+func getHandler(w http.ResponseWriter,r *http.Request){ fmt.Fprintf(w,"%d",visits*100) } // ISSUE: wrong scale factor