Use macros instead of magic values

c_primer_plus/chapter03/04.c

@@ -8,9 +8,9 @@ int main (void) {
 
   printf("Enter a floating-point value: ");
   scanf("%f", &a);
-  printf("fixed-point notation: %f\n", a);
-  printf("exponential notation: %e\n", a);
-  printf("p notation: %a\n", a);
+  printf("fixed-point notation: %.2f\n", a);
+  printf("exponential notation: %.2e\n", a);
+  printf("p notation: %.2a\n", a);
 
   return 0;
 

c_primer_plus/chapter03/05.c

@@ -2,6 +2,9 @@
 #include <limits.h>
 
 
+#define SEC_PER_YEAR 3.156e7
+
+
 
 int main (void) {
 
@@ -10,13 +13,12 @@ int main (void) {
   printf("Enter your age: ");
   scanf("%u", &age);
 
-  if ((unsigned int)(UINT_MAX / 3.156e7) < age) {
+  if ((unsigned int)(UINT_MAX / SEC_PER_YEAR) < age) {
     printf("Integer overflow\n");
     return 1;
   } else {
-    printf("You are %u seconds old\n", (unsigned int)(age * 3.156e7));
+    printf("You are %u seconds old\n", (unsigned int)(age * SEC_PER_YEAR));
+    return 0;
   }
 
-  return 0;
-
 }

c_primer_plus/chapter03/06.c

@@ -1,6 +1,9 @@
 #include <stdio.h>
 
 
+#define MOL_MASS 3.0e-23
+#define WATER_QUART_GRAM 950.0
+
 
 int main (void) {
 
@@ -8,7 +11,7 @@ int main (void) {
 
   printf("Enter a amount of water, in quarts: ");
   scanf("%f", &quarts);
-  printf("Number of molecules: %e\n", quarts * 950.0 / 3.0e-23);
+  printf("Number of molecules: %.2e\n", quarts * WATER_QUART_GRAM / MOL_MASS);
 
   return 0;