DATA TYPES
in
C Programming
1
Engr. Qazi Shahzad Ali
Kyungpook National University, South Korea

Four Types of Data
1- Fundamental Data
Types
4- User Defined Data
Types
2- Data Type Modifiers
3- Derived Data Types
2

1- Fundamental Data Types
1.1- Integer
1.2- Character
1.4- Double
1.5- Void
1.3- Float
FUNDAMENTAL DATA TYPES ARE THOSE
THAT ARE NOT COMPOSED OF OTHER
DATA TYPES
3

2- Data type modifiers
2.1- Integer Type
Modifiers
2.2- Character Type
Modifiers
2.3- Floating-point Modifiers
1-They change some properties
of the data type
2-The modifiers define the
amount of storage allocated to
the variable. Like short, double,
long
4

3- Derived Data Types
3.1- Arrays
3.3- Pointers
3.4- References
3.5- Constants
3.2- Functions
5

4- User Defined Derived Data
Types
4.1- Class
4.2- Structure
4.3- Union
4.4- Enumeration
6
Web link for study of Enumeration
http://cplus.about.com/od/introductiontoprogramming/p/enumeration.htm

The Decimal & Binary Number System
Binary Decimal
0000 0 max number that can be represent by= 2n -1
0001 1 n= number of bits
0010 2 for Example if we use 1 bit then we can represent only 0 &
0011 3 1 decimal number, if 2 bit then 2 and 3, if 3 bit then max
0100 4 up to 7 (23-1=8-1=7), Similarly if we use 8 bits in case of
0101 5 “char data type” then max (28-1=256-1=255),similarly in
0110 6 case of signed 1 bit out of 8 bits are used for plus or minus
0111 7 (0 for +, & 1 for -) so (Max27-1=128-1=127) & (Min-27=-128),
1000 8
1001 9
7

Name Description Size* Range*
char Character or small integer. 1byte
signed: -128 to 127
unsigned: 0 to 255
short int (short) Short Integer. 2bytes
signed: -32768 to 32767
unsigned: 0 to 65535
int Integer. 2bytes
signed: -32768 to 32767
unsigned: 0 to 65535
long int (long) Long integer. 4bytes
signed: -2147483648 to
2147483647
unsigned: 0 to 4294967295
float Floating point number. 4bytes 10 -38 to 1038 (~7 digits)
double
Double precision floating
point number.
8bytes 10 -308 to 10308 (~15 digits)
long double
Long double precision
floating point number.
10bytes 10 -4932 to 104932 (~19 digits)
8

Integer Modifier
TYPE APPROXIMAT
E SIZE
MINIMAL RANGE
SHORT 2 -32768 to 32767
UNSIGNED SHORT 2 0 to 65,535
SIGNED SHORT 2 Same as short
INT 2 -32768 to 32767
UNSIGNED INT 2 0 to 65,535
SIGNED INT 2 Same as int
LONG 4 -2,147,483,648 TO 2,147,483,647
UNSIGNED LONG 4 0 to 4,294,967,295
SIGNED LONG 4 Same as long
Note: The prefix signed makes the integer type hold negative values also.
Unsigned makes the integer not to hold negative values.
9

Char Modifier
TYPE APPROXIMATESIZE MINIMALRANGE
CHAR 1 -128 to 127
UNSIGNED CHAR 1 0 to 255
SIGNED CHAR 1 Same as char
Floating Point Modifier
TYPE APPROXIMATE SIZE DIGITS OF
PRECISION
FLOAT 4 7
DOUBLE 8 15
LONG DOUBLE 10 19
10

How to declare them
{
int Count;
Count = 5;
}
{
float Miles;
Miles = 5.6;
}
{
char Letter;
Letter = 'x';
}
Integer Declaration:
Float Declaration:
Character Declaration:
11

Signedness
• If signed, the most significant bit designates a positive or negative value leaving
the remaining bits to be used to hold a designated value. Unsigned integers can
only take non-negative values (positive or zero), while signed integers (default) can
take both positive and negative values.
• An unsigned character, depending on the code page, might access an extended
range of characters from 0 → +255, instead of that accessible by a signed char
from −128 → +127, or it might simply be used as a small integer. The standard
requires char, signed char, unsigned char to be different types. Since most
standardized string functions take pointers to plain char, many C compilers
correctly complain if one of the other character types is used for strings passed to
these functions
 unsigned int x;
 signed int y;
 int z; /* Same as "signed int" */
 unsigned char grey;
 signed char white;
12

INTEGER DATA TYPE
Integers are whole numbers.
Countable like # of rooms in a house
C has 3 classes/Modifier of integer
1. short int
2. int
3. long int
13

FLOAT DATA TYPE
• Decimal/Exponential Number
• Values that are measureable like length of
room 145.25 inches
• Store memory in two parts
1. Mantissa (The value of number takes 3 bytes)
2. Exponent (Power of number takes 1 byte)
Exp: 12345 will be represented as 1.2345e4 (4 is exponent & 1.2345 is
number)
• They have two advantages
1: they can represent values between integers.
2: they can represent a much greater range of values.
14

CHARACTER DATA TYPE
• Includes every printable character on the
standard English language keyboard
• We can show ASCII code with the help of
characters
• Example of characters:
– Numeric digits: 0 - 9
– Lowercase/uppercase letters: a - z and A - Z
– Space (blank)
– Special characters: , . ; ? “ / ( ) [ ] { } * & % ^ < > etc
15

DOUBLE DATA TYPE
• The data type double is also used for
handling floating-point numbers. But it is
treated as a distinct data type because, it
occupies twice as much memory as type
float, and stores floating-point numbers
with much larger range and precision. It is
slower that type float.
16

VOID DATA TYPE
• It specifies an empty set of values. It is
used as the return type for functions that
do not return a value. No object of type
void may be declared.
• It is used when program or calculation
does not require any value but the syntax
needs it.
17

C-Software Tools
In order to write a C program you will need:
• An Editor - Something to write code in.
• A Compiler - Converts the code into Machine
Language (object files).
• A Linker – Combines several object files into
one executable (written in Machine
Language).
• A Debugger – Provides supervised execution
of the code.
18

• A token is a language element that can be used in
forming higher level language constructs
• Equivalent to a ‘word’ in English language
• Several types of tokens can be used to build a
higher level C language construct such as
expressions and statements
• There are 6 kinds of tokens in C:
– Reserved words (keywords)
– Identifiers
– Constants
– String literals (constant)
– Punctuators
– Operators
Token
19

Reserved Words/Keywords
• Keywords that identify language entities such as
statements, data types, language attributes, etc.
• Have special meaning to the compiler
• cannot be used as identifiers/variable in our
program.
• Should be typed in lowercase.
• White in color
• Total numbers=32
• Example: const, double, int, main, void, while, for,
else (etc..)
20

Identifiers
• Words used to represent certain program
entities (program variables, function names,
etc).
• Example:
– int my_name;
• my_name is an identifier used as a program variable
– void CalculateTotal(int value)
• CalculateTotal is an identifier used as a function name
21

Punctuators (separators)
• Symbols used to separate different parts of the C
program.
• These punctuators include:
– [ ] ( ) { } , ; “: * #
• Usage example:
22
void main (void)
{
int num=10;
printf (“%d”,num);
}

C Constants
Primary Constants
Integer Constant,
Real Constant,
Character
Constant
Secondary
Constants
Array
Pointer
Structure
Union
Enum.etc
23

Constants
• Entities that appear in the program code as fixed
values.
• 3 types of Primary constants:
– Integer constants
• Positive or negative whole numbers with no fractional part
• Example:
– const int MAX_NUM = 10;
– const int MIN_NUM = -90;
– Floating-point constants
• Positive or negative decimal numbers with an integer part, a
decimal point and a fractional part
• Example:
– const double VAL = 0.5877e2; (stands for 0.5877 x 102)
– Character constants
• A single character enclosed in a single inverted commas
• Example:
– const char letter = ‘n’;
– const char number = ‘1’; 24

String Literal (Constant)
• A sequence of Character consisting of
Alphabets,didgits,and special character in
double quotation mark is call String Constant
Example “Pakistan” and “Lahore-58900”
25
Const Qualifier
• The data that follow the keyword “const” cannot
change its value during execution of program.
This can be replaced by Define directive
Example : const float p=3.14

Alphabets Words Sentences Paragraphs
Alphabets
Digits
Special
Symbols
Constants
Variables
Keywords
Instructions Program
Steps in learning English Language
Steps in learning C Language
26

C Development Environment
DiskPhase 2 :
Preprocessor
program
processes the
code.
DiskCompilerPhase 3 :
Compiler
creates object
code and stores
it on Disk.
Preprocessor
DiskLinkerPhase 4 :
Linker links object
code with libraries,
Creates and
stores it on Disk.
EditorPhase 1 :
Program is
created in the
Editor and
stored on Disk.
Disk
27

LoaderPhase 5 :
:
.
Primary
Memory
Loader puts
Program in
Memory
C P UPhase 6 :
:
.
Primary
Memory
CPU takes each
instruction and
executes it, storing
new data values as
the program executes.
28

From code to executables
Electrical.cpp
Electrical.obj
Electrical.exe
Electrical.bkp
Compiler
Linker
SaveSource File
cs.LIB
Library Files
29

C Development system
1.IDE( Integrated Development Environment)
2.Command Line Development System
C Directories
• TC = The Install program puts all the subdirectories and files in
this directory
• BIN=Executable files store in this sub-directory
• INCLUDE= Header Files (.h file extension)
• LIB=Following Files
a) Library Files
b) Run-Time Object Files
c) Math Libraries
which are combines during Linking process, are stored in this
sub-directory
30

Making An Application
Write the source code
Compile the code into
object files
Link several object files
into an executable
Run the application
We’ll focus on this
part
Don’t worry about
these parts
31

Variable names- Rules
• Should not be a reserved word like int etc..
• Should start with a letter or an
underscore(_)
• Can contain letters, numbers or
underscore.
• No other special characters are allowed
including space
• Variable names are case sensitive
– A and a are different.
32

Brackets
•< > Angle Brackets
•{ } Curly Brackets
•( ) Parenthesis
•[ ] Square Brackets
33

A Simple C Program Example
#include <stdio.h>
main()
{
printf("Programming in C is easy.");
}
Sample Program Output
Programming in C is easy.
Preprocessor
Directive
Header File
Program
Statement
Function (NOTE: no semicolon with
function)
NOTE: All commands in C must be lowercase.
34

1. program execution begins at main()
2. keywords are written in lower-case
3. statements are terminated with a semi-colon
4. text strings are enclosed in double quotes
5. printf() is actually a function (procedure) in C
that is used for printing variables and text
6. The text appears in double quotes "", it is
printed without modification. There are some
exceptions however.
Summary of major points
35

Preprocessor Directives
• The first thing to be checked by the compiler.
• Starts with ‘#’.
• Tell the compiler about specific options that it
needs to be aware of during compilation.
• There are a few compiler directives. But only 2 of
them will be discussed here.
– #include <stdio.h>
• Tell the compiler to include the file stdio.h during
compilation
• Anything in the header file is considered a part of the
program
– #define VALUE 10
• Tell the compiler to substitute the word VALUE with 10
during compilation
36

Header Files
• Messages to Compiler called compiler
directives
• “.h” file extension
• Tell the compiler about definition of words or
phrases used in program
• Have prototype for library function in order to
avoid program error.
Examples:
• stdio.h →(Standard Input/output)
• conio.h →(Console Input/output)
• iostream →(Input Output Stream)
37

Header files (Cont’d)
• The files that are specified in the include
section is called as header file
• These are precompiled files that has some
functions defined in them
• We can call those functions in our program
by supplying parameters
38

Four types of Header Files:
stdio.h
conio.h
ctype.h
math.h
39

Stdio.h (Standard Input/output )
40

conio.h (console input/output)
41

Math.h
42

ctype .h
43

main () Functions
• A C program consists of one or more functions
that contain a group of statements which perform
a specific task.
• C program must at least have one function: the
function main.
• The C programs starting point is identified by the
word main()
• This informs the computer as to where the
program actually starts. The Parenthesis () that
follow the keyword main indicate that there are
no arguments supplied to this program (this will
be examined later on).
• The two braces, { and }, signify the begin and
end segments of the program.
44

main function (Cont’d)
• This is the entry point of a program
• When a file is executed, the start point is
the main function
• From main function the flow goes as per
the programmers choice.
• There may or may not be other functions
written by user in a program
• Main function is compulsory for any c
program
45

Statements
• A specification of an action to be taken by the
computer as the program executes.
• In the previous example the line that terminate with
semicolon ‘;’ is a statement.
– printf ("Programming in C is easy.");
• If there are more than one line then each line is a
statement.
46

Define & Declaration
• Declaration: specifies the type of a variable.
– Example: int local_var;
• Definition: assigning a value to the declared
variable.
– Example: local_var = 5;
• A variable can be declared globally or locally.
• A globally declared variable can be accessed
from all parts of the program.
• A locally declared variable can only be
accessed from inside the function in which
the variable is declared.
47

Example of Define & Declaration:
#include <stdio.h>
#define VALUE 10
int global_var;
void main (void)
{
/* This is the beginning of the program */
int local_var;
local_var = 5;
global_var = local_var + VALUE;
printf (“Total sum is: %dn”, global_var); // Print out the result
}
} Preprocessor
directive
Global variable declaration Comments
Local variable declaration
Variable definition
48

Comments writing in C
language ‘//’ & ‘/*’ ‘*/’
• Explanations or annotations that are included
in a program for documentation and
clarification purpose.
• Completely ignored by the compiler during
compilation and have no effect on program
execution.
• Starts with ‘/*’ and ends with ‘*/’
• Some compiler support comments starting
with ‘//’
49

THANK YOU
50