C
PROGRAMMING CHAPTER 2
C Programming Tutorial-Chapter 2
============================
Things Covered In Chapter 2
Types of Data in C
How the Computer Stores Data
Formatting text using printf()
Placeholders
Escape Sequences
============================
I assume that you've read the first chapter of this tutorial.
Otherwise you can get it at:
http://tazforum.thetazzone.com/viewtopic.php?t=6453
Types of Data in C
This information may seem a bit superfluous at this stage, but read it
anyway because you won't undestand the next section (or the ramaining
chapters in the tutorial) without it.
In C, there are two basic types of data: numerical and string.
Numerical data is any number like say, 20 or 54.76 while string data is
alphanumeric data like say, "cgkanchi" or "hello world!". String data,
in C is always enclosed in double quotes so "20" is a string while 20
isn't (don't worry, it'll get clearer as you go along). Numerical data
in C is of three basic types:
1. char: As you might guess, char data consists of single characters
(which are just numbers to the computer). But char data can also store
numbers in the range of -128 to +127 (I'll get to that in the next
section). char data (when used to store characters) is always enclosed
in single quotes, like so 'c'.
2. int: Integer data stores whole numbers from -32,768 to +32,767.
3. float: Float or floating point data is used to store decimal numbers
between 3.4 x 10 ^ -38 to 3.4 x 10 ^ 38 (10 ^ 38 is read as 10 to the
power 38. So 2 ^ 2 would be 2 to the power 2 or two squared which is 4).
What about bigger numbers? Well there's a long data type to store
integer data between -2,147,483,648 to 2,147,483,647 and the double
data type to store data between 1.7 x 10 ^ -308 to 1.7 x 10 ^ 308. What
about char? There is no such thing as a long char but if you want to
store a number greater than 127 then just use an int instead. You can
also qualify any of these types as unsigned which means all data they
store is positive or zero. So the range of char changes from -128 to
127 to 0 to 255, that of int changes from -32,768 to 32,767 to 0 to
65,535 and so on. For some background information on how exactly the
computer stores data read the next section. Otherwise, just skip to the
section on screen output.
How the Computer Stores Data
The computer is a digital creature. So it stores everything and I mean
EVERYTHING in the form of numbers. Actually it stores all the data that
you put into it as binary code. So, to the computer, any data is stored
in the form of 1s and 0s. The computer has small compartments of data
called bits. Every bit can store either a 1 or a 0. In other words, a
bit can have only one value at any given time. Now, eight bits make a
byte. A data which is qualified as char occupies one byte of memory.
Similarly, int data occupies 2 bytes, float and long data 4 bytes and
double data 8 bytes. Given seven places, each of which has two possible
values (in this case 0 and 1), there are 128 possible combinations.
That's why a char has a range of -128 to 127. What about the eighth bit
you ask? Well, the eighth bit is called the sign bit and is used to
store the sign of the number. When you qualify data as unsigned, the
sign bit isn't used. Given eight places, each with two possible values,
there are 256 possible combinations. That makes the range of an
unsigned char into 0 to 255.
Formatting Text Using printf()
We ended our last chapter with an analysis of the hello.c program.
Remember the statement that does most of the work in the program? Yes
I'm talking about the printf("Hello World!"); thing. "printf" stands
for "print formatted" and is one of the most popular ways to output
text to the screen.
Type in this program to see the different types of data:
Code:
/*data.c
A program to illustrate the
different types of data*/
#include <stdio.h>
void main()
{
printf("This is char data:
%c\n",'A');
printf("This is char data in
numerical form: %c\n",65);
printf("This is int data %d:\n",65);
printf("This is float data:
%f\n",65.00);
printf("This is float data with only
two decimals data: %.2f\n",65.00);
printf("This is double data:
%2f\n",65.00);
printf("This is a string:
%s","Hello");
}
Save this program as data.c . Compile. Fix errors. Run.
This program is very similar to the hello.c program in chapter 1 except
that it has many printf statements. The major difference is the
%something things. The % sign followed by a letter is known as a
placeholder. What a placeholder does is that it tells the printf
statement to look for a particular type of data after the final double
quote("). You can have multiple placeholders in a single statement. In
this case, the printf statement looks for data in the order in which
the placeholders appear.
Here is a list of placeholders and what they do:
Placeholder What it does
%c Displays char data
%i, %d Display int data
%f Displays float data
%2f Displays double data
%.2f Displays float with the requisite
number of decimals as
specified after the period(.)
%s Displays string data
%o Displays octal data (more on octal
and hexadecimal in another chapter)
%x Displays hexadecimal data
As the % sign has a special meaning for printf, to display it, you must
double it up. For example, printf("Something%%"); will display
Something%
Remember the "\n" thing that makes the printf statement go to the next
line? That is called an escape sequence. Escape sequences consist of a
backslash(\) and a letter following them. Escape sequences can be used
to do a lot of interesting things in C. They are used simply by tagging
them on at any point in a string. For example printf("Hel\nlo"); makes
the program display "Hel" on one line and "lo" on the next.
Here is a list of some of the escape sequences:
Escape Sequence What it does
\n Goes down to the beginning of the next line
\r Goes back to beginning of line
\t Prints a tab
\ Goes down one line without going
back to the beginning of the line
\x Recognizes the next characters(upto
the next space) as hexadecimal
numbers
\o Recognizes the next characters(upto
the next space) as octal numbers
\a The computer speaker lets out a
beep
\b Goes back one character
In addition to these certain characters have a special meaning for the
printf function. So to display them you must precede them by a
backslash. The two most notable ones are the backslash itself and the
double quotes("). So, to display a backslash you'd type "\\" and to
display double quotes you'd type "\""(the first and the last are the
double quotes for the string and the middle one is the one you want to
display).
So, that's all for chapter 2 of my C tutorial. Until next time, I'll
give you a few assignments to do.
1. Write a program to display the sentence "I Love C", said the
programmer. (With the quotes).
2. Write a program to display
Hello!
Hi!
Howdy!
Using only a single printf statement. (Hint: remember \n).
3. Write a program to display "C:\ABC\ABC\" (without the quotes).
Don't hesitate to ask any doubts or questions related to the tutorial.
And experienced programmers who happen to read this, please fill in any
placeholders or escape sequences I might have missed.
Cheers,
cgkanchi
Original Tutorial
by cgkanchi for TheTAZZone-TAZForum
Originally posted on April 19th, 2007 here
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