"HELLO WORLD" EXERCISES

READING 
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Programming Assignment 0
Notes for lecture 1
Kernighan and Ritchie, 1.1 1.2 1.3

SUPPLEMENTAL READING
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Deitel and Deitel, Chapters 1 and 2


EXERCISES
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 1. Is the following progam legal?

          #include <stdio.h>
          main() {
             int x, y;
             scanf("%d %d", &x, &y);
             printf("%d\n", x + y);
          }

 2. Write a program that reads in two integers and prints their sum.

 3. Write a program that prints "hello world" 5 times.

 4. Write a program that reads in a number and prints out "hello world"
    that many times.






























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		  ANSWERS TO "HELLO WORLD" EXERCISES


1. It depends on what the definition of "is" is.  The C standard, which was
   instituted in the late 1980s, requires that we say "void main()", but not
   everyone pays attention to that.  Some say that death and destruction will
   ensue unless everyone uses the standard; others prefer a more laissez-faire
   attitude that saves programmers from typing useless jargon.  The "lcc"
   compiler enforces all the rules to help you learn them (if you want to);
   you can also use the "cc" or "gcc" compilers, which may sometimes view
   your program differently.  In this case, both "cc" and "gcc" provide
   the "void" by default if you don't type it.

          % lcc hello.c
          hello.c:5: warning: missing return value
          % gcc hello.c
          % cc hello.c
% 

2.
          #include <stdio.h>
          int main(void) {
             int x, y;
             scanf("%d %d", &x, &y);
             printf("%d\n", x + y);
             return 0;
          }

3.
   Brute-force solution:

          #include <stdio.h>
          int main(void) {
             printf("hello, world\n");
             printf("hello, world\n");
             printf("hello, world\n");
             printf("hello, world\n");
             printf("hello, world\n");
             return 0;
          }

   Better solution:

          #include <stdio.h>
          int main(void) {
             int i;
             for (i = 0; i < 5; i++)
                printf("hello, world\n");
             return 0;
          }

4.
          #include <stdio.h>
          int main(void) {
             int i, n;
             scanf("%d", &n);
             for (i = 0; i < n; i++)
                printf("hello, world\n");
             return 0;
          }