Solved #510- Storage_Classes.md

docs/day-10/Storage_Classes.md

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+# Storage classes in C
+
+A *storage class* in C specifies the scope, lifetime, and initialization behavior of variables. Each variable in C has one storage class. Variables declared within a block have automatic storage by default, unless specified with **`extern`**, **`static`**, or **`register`**.
+
+## Auto Storage Class
+
+The `auto` storage class is used to define local variables within a block. Variables declared as `auto` are automatically initialized with garbage values.
+
+```c
+#include <stdio.h>
+
+void main() {
+    auto int num = 10;
+    printf("Value of num: %d\n", num);
+}
+```
+
+## Register Storage Class
+
+The `register` storage class is used to define local variables within a block that are stored in the CPU register for faster access. Modern compilers often optimize register allocation, making explicit use of `register` unnecessary in most cases.
+
+```c
+#include <stdio.h>
+
+void main() {
+    register int count;
+    for (count = 0; count < 5; count++) {
+        printf("Count: %d\n", count);
+    }
+}
+```
+
+## Static Storage Class
+
+### Static Variable within Function
+
+The `static` storage class is used to define variables that are initialized only once and retain their values between function calls.
+
+```c
+#include <stdio.h>
+
+void func() {
+    static int x = 0;
+    x++;
+    printf("x = %d\n", x);
+}
+
+void main() {
+    func();
+    func();
+    func();
+}
+```
+
+### Static Global Variable
+
+```c
+#include <stdio.h>
+
+static int count = 5;
+
+void func();
+
+void main() {
+    while (count--) {
+        func();
+    }
+}
+
+void func() {
+    static int i = 5;
+    i++;
+    printf("i is %d and count is %d\n", i, count);
+}
+```
+
+## Extern Storage Class
+
+The `extern` storage class is used to declare a variable that is defined in another file or scope. It extends the visibility of a variable to the entire program.
+
+```c
+// File1.c
+
+#include <stdio.h>
+extern int count;
+
+void main() {
+    count = 5;
+    printf("Count in File1: %d\n", count);
+    func();
+}
+
+// File2.c
+
+#include <stdio.h>
+int count;
+
+void func() {
+    count++;
+    printf("Count in File2: %d\n", count);
+}
+```
+
+```