diff --git a/ex21.c b/ex21.c
new file mode 100644
index 0000000..29baa51
--- /dev/null
+++ b/ex21.c
@@ -0,0 +1,18 @@
+#include <stdint.h>
+#include <stdio.h>
+
+
+int main(int argc, char *argv[])
+{
+    printf("sizeof(int8_t) = %d\n", sizeof(int8_t));
+    printf("sizeof(uint8_t) = %d\n", sizeof(uint8_t));
+    printf("sizeof(int16_t) = %d\n", sizeof(int16_t));
+    printf("sizeof(uint16_t) = %d\n", sizeof(uint16_t));
+    printf("sizeof(int32_t) = %d\n", sizeof(int32_t));
+    printf("sizeof(uint32_t) = %d\n", sizeof(uint32_t));
+    printf("sizeof(int64_t) = %d\n", sizeof(int64_t));
+    printf("sizeof(uint64_t) = %d\n", sizeof(uint64_t));
+
+
+    return 0;
+}