Transcript Power Point Version

Program Development Cycle
1. Edit program
2. Compile program
- translates it from C to
machine language
3. Run/execute your program.
4. If not satisfied, go back to #1.
My First C Program
/* Arup Guha
My First C Program
8/23/07
COP 3223 Rocks! */
#include <stdio.h>
int main(void) {
printf(“COP 3223 Rocks!\n”);
return 0;
}
Purpose of Comments
• To tell the reader basic information about
the program
– Who wrote it
– When they wrote it
– What it does
– Any other useful information about it
• Inside code, they inform the reader about
the specific function of a group of
statements.
#includes
• Tells the compiler that you may be using
prewritten C functions for a particular
library.
• We will always use stdio.h – it allows us to
do standard input and output.
• When you call a function for a C library, it
will look to all of the libraries you have
included to find out HOW to run the
function.
Function main
• The only code directly executed is the
code inside of main
• The beginning and ending are delineated
by { and }, respectively.
• Everything else is run in sequential order,
as it is listed.
• Other functions (like printf) ONLY run if
they are called from main, OR from
another function called by main, etc.
printf
• Prewritten C function in stdio.h
• Prints out everything inside of “” exactly
with these exceptions
– A backslash and the character after it
– A percent sign and the character after it
• Prints go in order, and the cursor starts
where the last print ended.
Exceptions for prints
• Backslash – Escape Sequence
– \n is a newline
– \t is a tab
– \\ is a backslash
– \” is a double quote
• Percent Codes (Will be explained later)
– %d (for integer variable)
– %lf (for double variable)
– %c (for character)
Variables
• Types we will commonly use
– int
– char
– double
• How to Declare a Variable
– <type> <name>;
• Examples
– int value;
– char my_letter, your_letter;
– double money;
Assignment Statement ( = )
•
•
•
ONE EQUAL SIGN, NOT TWO
Syntax: <variable> = <expression>
What it does:
1. Calculates the value of <expression> at that
point in time.
2. Changes the value of <variable> to this
NEW value.
/* Arup Guha
My Second C Program
8/23/07
Computes the number of feet in a mile */
#include <stdio.h>
int main(void) {
// Declare variables
int feet_in_mile, yards_in_mile;
int feet_in_yard;
// Make calculation
yards_in_mile = 1760;
feet_in_yard = 3;
feet_in_mile = yards_in_mile*feet_in_yard;
// Output the result
printf(“Mile = %d Feet.\n”, feet_in_mile);
return 0;
}
% code explanation
• If %d or a similar percent code is
encountered inside “” of a printf, this is
what happens
– An expression must be specified after the end
of the double quote, separated by a comma
– Value of this expression is printed in the
FORMAT of the type specified by the percent
code.
– Experiment to see what happens if you use
the wrong percent code.