diff --git a/bi to dec b/bi to dec
new file mode 100644
index 0000000..e54ca46
--- /dev/null
+++ b/bi to dec	
@@ -0,0 +1,46 @@
+// program to convert decimal number into binary and binary into decimal number
+#include<stdio.h>
+void binary(int n)
+{
+    int rem;
+    if(n<=1)
+    {
+        printf("%d",n);
+        return;
+    }
+    rem=n%2;
+    binary(n/2);
+    printf("%d",rem);
+}
+int main()
+{
+    int n,c,d=0,b=1,r;
+    printf("1. For decimal to binary\n");
+    printf("2. for binary to decimal\n");
+    scanf("%d",&c);
+    printf("enter number to convert\n");
+    scanf("%d",&n);
+    if(c==1)
+    {
+        if(n<0)
+        {
+            printf("not possible\n");
+        }
+        else
+        {
+            printf("The decimal -> binary is ");
+            binary(n);
+        }
+    }
+    else if(c==2)
+    {
+        while(n>0)
+        {
+            r=n%10;
+            d=d+(b*r);
+            n=n/10;
+            b=b*2;
+        }
+        printf("The binary -> decimal is %d\n",d);
+    }
+}