Introduction to Computer Programming
September 8, 2008
1
Required readings
How many lines of code have you written? Let
n
be your answer. If
n
is zero,
you
must
read Chapter 2 of the textbook twice carefully. If
n
is between 1 and
1
,
000, you should read Chapter 2 once.
If
n
is greater than 1
,
000, you can
safely ignore Chapter 2, and proceed to Chapter 3.
2
Convert the above requirements to C code
The requirements in Section 1 can be easily converted to a C program, which,
based on our input,
n
, tells us what we should do.
read.c
is the source file for
the program. See Section 3 for detailed explanations.
/* read.c */
#include <stdio.h>
void read_ch2_twice()
{
printf(‘‘:( I must read Chapter 2 twice carefully!\n’’);
}
void read_ch2_once()
{
printf(‘‘I should read Chapter 2 once.\n’’);
}
void ignore_ch2()
{
printf(‘‘:) I can safely ignore Chapter 2.\n’’);
}
/*
1
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* Input the number of lines of code that you have written.
Hit Enter
* key.
Follow the instructions given by the computer.
*/
int main()
{
int n;
printf(‘‘How many lines of code have you written? ‘‘);
if (scanf(‘‘%d’’, &n) < 1 || n < 0)
return 1;
if (n == 0) /* no lines? */
read_ch2_twice();
if (n > 0 && n <= 1000) /* some lines? */
read_ch2_once();
if (n > 1000) /* enough lines? */
ignore_ch2();
return 0;
}
3
Explanation
When we see a
/* */
pattern, this is a C’s comment. The comment helps us
(not computers) understand the code. As we will see below, a comment may
occupy only one line, or may occupy multiple lines.
/* read.c */
/*
* Input the number of lines of code that you have written.
Hit Enter
* key.
Follow the instructions given by the computer.
*/
When we see
#include
, this is a C’s preprocessor directive.
#include
<stdio.h>
inserts the contents from the file
stdio.h
into the current file,
read.c
. If we check
stdio.h
, we will find this line:
extern int printf (__const char *__restrict __format, ...);

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- Fall '01
- na
- C Programming, Computer Programming, Return statement, Void type
-
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