add last lesson of chapter 1

intro/ext_var_and_scope.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+
+#define MAXLINE 1000   /* maximum input line size */ 
+
+int max;               /* maximum length seen so far */ 
+char line[MAXLINE];    /* current input line */ 
+char longest[MAXLINE]; /* longest line saved here */ 
+
+int my_getline(void);
+void copy(void);
+
+
+/* print longest input line; specialized version -> worse, less general */ 
+main()
+{
+  int len;
+  extern int max;
+  extern char longest[];
+
+  max = 0;
+  while ((len=my_getline()) > 0)
+    if (len > max) {
+      max = len;
+      copy();
+    }
+  if (max > 0)    /* there was a line */ 
+    printf("%s", longest);
+  return 0;
+}
+
+
+/* getline: specialized version */ 
+int my_getline(void)
+{
+  int c, i;
+  extern char line[];
+
+  for (i = 0; i < MAXLINE-1 && (c=getchar()) != EOF && c != '\n'; ++i)
+    line[i] = c;
+  if (c == '\n') {
+    line[i] = c;
+    ++i;
+  }
+  line[i] = '\0';
+  return i;
+}
+
+
+/* copy: specialized version */ 
+void copy(void)
+{
+  int i;
+  extern char line[], longest[];
+
+  i = 0;
+  while ((longest[i] = line[i]) != '\0')
+    ++i;
+}