Hi

1stint.c

@@ -1,6 +1,13 @@
 #include<stdio.h>
  int main()
 {
-	int no = 20;
-	printf ("The value is %d",no);
+	int no;
+	printf("Enter a number: ");
+	scanf("%d",&no);
+	if(no < 0)
+		printf("Invalid no.!!!");
+	else{
+		printf ("The value is %d",no);
+	}
+	return 0;
 }

Addition

@@ -0,0 +1,9 @@
+#include <stdio.h>
+int main(void) {
+   int a = 545;
+   int b = 123;
+   printf("The first number is %d and the second number is %d \n", a , b);
+   int sum = a + b;
+   printf("The sum of two numbers is %d" , sum);
+   return 0;
+}

even.c

@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+int main() {
+	int i;
+	printf("Even numbers between 1 to 50 (inclusive):\n");
+	for (i = 1; i <= 10; i++) 
+	{
+		if(i%2 == 0) 
+		{
+		  printf("%d ", i);
+		}
+	}
+	return 0;
+}

greatestnumber.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+int main()
+
+{
+
+int ch=3;
+
+switch(ch)
+
+{
+
+default: printf(“Default”);
+
+case 1: printf(“option1”); break;
+
+case 2: printf(“option2”); break;
+
+}
+
+return 0;
+
+}
+
+
+