The Task

Programming Environment

The Programs

1. Write an ansi C program called hello.c that prints out Hello World! on a line.
2. Write an ansi C program called output.c. It should contain the following declarations:

   char c = 'a';
   short s = 55;
   int n = 5;
   long int nn = 22l; /* that's ell, not one. Can also use = 22L */
   long long int nnn = 33ll /* can also use = 33LL */
   float x = 7.5f;
   double y = 99.1234567;
   long double z = 99.5L;
   char someString[] = "This is some string.";
   		

   BUT DO NOT copy and paste. Type it in.
   
   It should use printf() to produce exactly the following output:

   c as an integer: 97
   c as a character: a
   s is 55
   n is 5
   nn is 22
   nnn is 33
   x is 7.500
   y is   99.12
   z is 99.500000
   someString is This is some string.
   "someString" is "This is some string."
   		

   The last item output, like all the others, should end with a newline character.
   Recall that the printf() function is invoked as printf(format string, additional arguments). In the printf() statements, use the variable names for the additional arguments, not the value of the variable. For example, use printf(" ... ", n), not printf(" ... ", 55).


3. Write an ansi C program called input.c. It should contain the following declarations:

   int a, b, c;
   int scanfReturnValue; 
   		

   Write code to read in values for a, b and c from standard input and then print out the values read. First print out the value returned by scanf in each case. The statement to read in the values and assign them to a, b and c would look like this:

   scanfReturnValue = scanf("%d %d %d", &a, &b, &c);
   printf("scanf returned %d\n", scanfReturnValue);
   printf("a = %d, b = %d, c = %d\n", a, b, c);
   		

   Look at the scanf() statement. The "%d" says you're expecting to read in an int (in decimal/base 10) and the "&" before the a, b and c indicates the address where a, b, c are stored and scanf reads the input values entered and stores them at these addresses. (Remember that C, like java, is pass by value.) Running your program might produce results like this:

   $ 
   $ input
       45
           33
     22
   scanf returned 3
   a = 45, b = 33, c = 22
   $ 
   $ 
   		

   The first 3 lines are echoed program input; the last 2 are program output.
   
   Try putting some numbers into a file and then redirecting standard input to come from the file, as in:

   $ input < fileName
   		

   What happens if there are ...
   more than 3 numbers in the file?
   fewer than 3?
   none?
   2 integers and then a double like 5 7 15.75?
   some text like 5 7 hello?
   or 5 7 99hello?


4. In the last exercise, you saw how to use scanf() to read in an integer. Of course, you'll want to use it to read in all kinds of values. In this exercise, you'll redo the first exercise, but instead of the variable values being given explicitly with numeric or string literals, they'll be assigned using scanf(). Before, you had

   char c = 'a';
   short s = 55;
   int n = 5;
   float x = 7.5f;
   double y = 99.1234567;
   long double z = 99.5L;
   char someString[] = "This is some string.";
   

   Now, instead, you'll start with

   char c;
   short s;
   int n;
   float x;
   double y;
   long double z;
   char someString[];