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UNIT I
1
STRUCTURE OF C PROGRAM
Unit Structure
1.0 Objectives
1.1 Introduction
1.2 C header and body
1.3 Comments
1.4 Interpreters v/s Compilers
1.5 Python v/s C
1.6 Program Compilation
1.7 Formatted Input Output Functions
1.8 Summary
1.9 Unit End Questions
1.0 OBJECTIVES  Understa nding the structure of c programming language
 Understanding the working of header files
 How to use comments in a c program
 Understanding the concept of interpreters and compilers
 Working with compilation and execution of program
 Understanding the structure of formatted input and output functions
1.1 INTRODUCTION History of C language :
C programming language was developed by Dennis Ritchie in the year
1972 at AT & T Bell laboratories. It is a general purpose, imperative and
procedural language. Mainly this language was invented to write UNIX
operating system. It means UNIX is totally written in C. C was initially
used for making up the operating systems because it produces the code
which runs as fast as assembly language.
There is a similarity between any l anguages eg. English language and any
programming language. Because when we learn English language We start
learning alphabets first then we start forming words then small sentences
and then we write paragraphs. Similarly when we are considering C
languag e first we start learning alphabets, digits and special characters
then we come to know keywords, constants and variables then in next munotes.in

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2 Structure of C Program phase we do follow instructions and the last phase where we are able to
write the program.
What is Program:
So when we tr y to define the word Program we can define it as “A set of
instructions to be followed with rules in a sequential manner to get the
desired output”. To understand this definition in a very well manner we
have to keep in mind certain things such as
1. It is a set of instructions (not just a single instruction) .
2. While writing a program rules related to it must be followed .
3. Sequence of the instructions must be taken care of. If sequence is
broken it will not give us the expected output.
To understand the import ance of sequence of instructions we will consider
the simple example of tea preparation
Eg: If Tea preparation is our program in that case we have to follow
following instructions:
1. Switch on the fire and put a vessel on it
2. Add water
3. Add sugar and tea pow der
4. Let it boil
5. Add milk and let it boil for a while
So in these 5 steps we will get our expected output i.e. tea. But if
suppose we are following the instructions such as:
1. Add sugar and tea powder
2. Let it boil
3. Add milk and let it boil for a while
4. Add w ater
In this second case we can see that we have followed all the instructions
but not in a proper sequence and hence we will not get the desired
output.so one can understand that sequence is most important in any
program. The word “ कार्यक्रम” is most suit able for program. As “कार्य”
means work or function and “ क्रम” means sequence. Hence it says
program means the work to be done in a sequence.
Features of C:
C is widely used language and it has following features : munotes.in

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3 Programming With C


1. Simple : The language is simple and ea smy to understand as it
provides structural approach i.e. it used to break the program in
various parts
2. Portable : C is a machine independent and portable language and it
can be compiled and run on different machine with some changes.
3. Extensible : Program s written in C language can be extended means
in existing feature and operations of a program new features and
operations can be added.
4. Fast and Efficient : C language is having lessor inbuilt functions as
compared to languages like python and hence overhe ad is less as well
as it directly interact with computer hardware and hence leads to
increase in speed
5. Statically typed : Whenever a programmer types a program he /she
has to mention types of variables used because types of variables are
checked at compile time and not run time. Hence it is a statically
typed language.
6. Rich function library : C provides lot of inbuilt functions which
results in fast development
7. Mid Level Language : C is intended to do low level programming
such as developing system applicatio n as well as it also support high
level language features and hence it is called as mid level language
8. Memory Management: C language support dynamic memory
allocation. The allocated memory can be made free whenever we need
using free() function.
9. Reusabilit y: C enables the feature of function call inside the function
i.e. recursion which leads to code reusability through backtracking . munotes.in

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4 Structure of C Program 1.2 C HEADER AND BODY To write a C program one must follow the given below rules:


1. Inclusion of Header Files : The header f iles in C contains C function
declaration and macro definitions which are to be shared between
several source files. Header files serve two purposes.
 System header files declare the interfaces to parts of the operating
system. Whenever they are included in the program they supply the
definitions and declarations to invoke system calls and libraries.
 When we create our own header files containing declarations for
interfaces between the source files of your program. Each time a
group of related declarations and macro definitions all or most of
which are needed in several different source files, in such cases
instead of writing all those declarations again and again it is a good
idea to create a header file for them.
These header files are always included in the C program with a pre -
processor directive „# include‟.
Conventionally the C header files are having an extension .h and name of
the file can contain o nly letters, digits, dashes, and underscores and at
most one dot.


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5 Programming With C Examples of header files are: Sr.No. Header File Type of Functions 1 Diagnostics Functions 2 Character Handling Functions 3 Localization Functions 4 Mathematics Functions 5 Nonlocal Jump Functions 6 Signal Handling Functions 7 Variable Argument List Functions 8 Input/Output Functions 9 General Utility Functions 10 String Functions 11 Date and Time Functions
2. Inclusion of main() function :
main () is the only function in C language which is self executable in
nature. It is a primary function and acts a starting point for program
execution. All the instructions of a program sh ould be enclosed within the
scope of main() function only. A program usually starts its execution in
the beginning of main() and stops the execution at the end of main(). This
is the reason we never write main(); means we are not putting (;) after
main() . Because if we put (;) after main() it will terminate the main()
function and thereby will not be able to execute the instructions written
inside main().
We either can write main() or void main(). However if we just write
main() in that case we should r eturn some value at the end. Whereas when
we are writing void main() we are making it clear to main() function that
there is no need to return any value.
3. Variable Declaration :
The next thing what we have to after opening main() function is
declaration of variables. In C language compulsorily the variables are to
be declared explicitly with its datatypes before using them. We can declare
and use the variable at the same time as we can do in various high level
languages.
4. Use of ; (semicolon) :
Every languag e is having its own grammar synonymously in programming
languages we used to call it as syntax. As per the syntax every instruction
in c language is terminated with the help of (;) semicolon. However some
exceptional statements are there which must not b e terminated using
semicolon. Eg : main() function , conditions, loops etc. These are the
statement on which something is dependent and if they are terminated the
dependent statements can not be executed. So the statements on which
something is dependent can not be terminated using (;) semicolon. munotes.in

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6 Structure of C Program 5. Use of lower case coding :
C is not a loosely typed language it directly interacts with hardware and so
all the instructions in C language must be compulsorily to be typed in
small case only. Certain things such a s name of the variables or messages
which are to be printed can be in capital case.
1.3 COMMENTS Comments are non executable statements used as annotation or
explanation of the source code which is readable by the programmer only.
C language provides two different types of comments:
1. Single line comment : For a single line commet // (double slash) can be
used.
Eg: // Comment goes here
2. Multiline comment : For multiline comments we use /* symbol for
starting and */ for ending the comment
Eg: /* comments are non executable statements
Comment goes here */
1.4 INTERPRETERS V/S COMPILERS Compilers and interpreters are programs that enables to conversion of
source code into machine code. Computer programs are normally written
in high level language ie. Human un derstandable language whereas
computers understand only machine language ie. Binary language ie. 0
and 1 only. So to enable the communication between human being (high
level language) and computer (machine language) there is a need of
language translator s. Interpreters and compilers both are working as
language translators. However the functioning of both is different.
Working of Interpreters:
An interpreter is a software program which transl ates a program source
code into a machine language ie 0 and 1 . However, the source code is
interpreted line-by-line whle running the program. If there is any error in
any line it leaves that line and moves to the next line and try to interpret it.
At the end whichever lines it has interpreted successfully on that basis it
generates the output and shown to the user.





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Working of Compilers :
A compiler is also a software program that follows the syntax rule of
programming language to convert a source code to machine code. It
cannot fix any error if present in a program; it generates an error message,
and it has to be corrected by the programmer in the program's syntax. If
the written program is errorless then the compiler converts entire source
code into machine code. A compiler converts complete source code into
machine code at once. And finally, the program get executed.


Interprter v/s Compiler : Sr.No. Interpreter Compiler 1 The program code is interpreted one line at a time The program is compiled at one stretch 2 Line by line code is scanned and encountered errors are shown All the errors are shown at the end of scanning process 3 Requires more time for execution Time required for execution is vey less 4 Doesn‟t convert source code into object code Converts source code into object code 5 Examples :Python, Ruby, Perl, MATLAB Examples : C, C++, C# munotes.in

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8 Structure of C Program 1.5 PYTHON V/S C C and python are very similar languages and are used for development of
various applications. Sometimes it becomes very difficult to decide when
to use python and when to use C. Whereas the difference between c and
python is that c is a structured programming language widely used for
hardware related applications such opera ting system development and
python is a multi paradigm general purpose language used for machine
learning, natural language processing and web development.
Following table will illustrate the difference between python and C in a
more easy way: Sr.No. Python C 1 Python is an interpreted, high-level, general-purpose programming language C is a general -purpose,
procedural computer
programming language. 2 Interpreted programs execute slower as compared to compiled programs. Compiled programs execute
faster as compared to interpreted
programs 3 It is easier to write a code in Python as the number of lines is less comparatively Program syntax is harder than Python 4 There is no need to declare the type of variable. Variables are untyped in Python. A given variable can be stuck on values of different types at different times during the program execution In C, the type of a variable must be declared when it is created, and only values of that type must be assigned to it. 5 Error debugging is simple. This means it takes only one in instruction at a time and compiles and executes simultaneously. Errors are shown instantly and the execution is stopped, at that instruction In C, error debugging is difficult as it is a compiler dependent language. This means that it takes the entire source code, compiles it and then shows all the errors 6 Supports function renaming mechanism i.e, the same function can be used by two different names. C does not support function renaming mechanism. This means the same function cannot be used by two different names munotes.in

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9 Programming With C 7 Syntax of Python programs is easy to learn, write and read The syntax of a C program is harder than Python 8 Python uses an automatic garbage collector for memory management In C, the Programmer has to do memory management on their own. 9 Python is a General-Purpose programming language C is generally used for hardware related applications 10 Python has a large library of built-in functions C has a limited number of built-in functions 11 Gives ease of implementing data structures with built-in insert, append functions Implementing data structures requires its functions to be explicitly implemented 12 No pointers functionality available in Python Pointers are available in C
1.6 PROGRAM COMPILATION Installation Process : C software can be downloadable freely and easily
available.
Link to download C software : https://developerinsider.co/download -
turbo -c-for-windows -7-8-8-1-and-windows -10-32-64-bit-full-screen/
Steps for installation :
1. Download the software using above link
2. Extract downloaded “Turbo C++3.2.zip” file
3. Run the setup.exe file
4. Follow the setup instructions
After following all the instructions fo llowing icon will get ceated on
desktop:

Steps for program compilation and execution :
1. Double click on Turbo C++ icon and then click on start Turbo C++
a text editor will open like this:

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10 Structure of C Program


2. Click on File option New menu following screen will appear. It is
nothing but a text editor where actually can write the source code. The
default name is „NONAME00‟ and extension is „.cpp‟. However since
we are writing program for C, extension should be given as „ c‟.


3. Write a source code here and save it with pro gram name. Extension.
By default the C programs used to get stored on the path
C:\Turboc3 \Bin . Here name of the prog ram is sample and extension is
c.
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11 Programming With C
4. Compile the program by pressing the shortcut key Alt + F9. The
Following screen will appear. He re it is showing success and hence we
can execute this program.


5. To execute the program press Ctrl + F9. It wil l display the output as
follows:



1.7 FORMATTED INPUT OUTPUT FUNCTIONS C provides standard functions scanf() and printf(), for performing
formatted input and output .These functions accept, as parameters, a
format specification string and a list of variables.
The format specification string is a character string that specifies the data
type of each variable to be input or output and the s ize or width of the
input and output.
Formatted input function :
The scanf() function is used for inputs formatted from standard
inputs and provides numerous conversion options for the printf()
function.
Syntax:
scanf(format_specifiers, &data1, &data2,……) ; // & is address operator munotes.in

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12 Structure of C Program The scanf() function reads and converts the characters from the
standard input according to the format specification string and stores
the input in the memory slots represented by the other arguments.
Example:
scanf(“%d %c”,&dat a1,&data2); In the case of string data names, the data name is not prefixed with
the &.
Formatted Output Function:
The printf() function is used for output formatted as the standard
output according to a format specification. The format specification
strin g and the output data are the parameters of the printf() function.
Syntax:
printf(format_specifiers, data1, data2,…..... ); Example :
printf(“%d %c”, data1, data2); The character specified after % is referred to as a conversion
character because it al lows a data type to be converted to another
type and printed.
1.8 SUMMARY C is a mother of all languages. It is a general purpose imperative and
procedural language. C was initially used for making up the operating
systems.
Program is “A set of instructio ns to be followed with rules in a sequential
manner to get the desired output”.
C is simple, portable, extensible, fast as well as efficient. It has a rich
library of functions.
While writing a c program 5 rules are to be kept in mind such as including
header files, including main() function, variable declaration , using lower
case coding and for statement terminaton semicolon is used.
Single line comments are denoted by // symbol and multiline comments
are denoted by /* */ symbol
Interpreters are t he language translators which interprets the code line by
line
Compilers are the language translators which compiles the source code at
a single stretch
Printf() is a formatted output function and scanf() is a formatted input
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13 Programming With C 1.9 UNIT END QUESTION S 1. Explain feature of C
2. Explain in brief the rules to be followed while writing a C program
3. What are header files? Explain its use also list out the header files
used in C
4. Write short note on interpreters
5. Write short note on compiler
6. Write difference betw een interpreter and compiler
7. Compare Python v/s C
8. Write short note of formatted input and output functions





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2
DATATYPES IN C
Unit Structure
2.0 Objectives
2.1 Introduction
2.2 Keywords and Identifiers
2.3 Variables and Constants
2.4 Datatypes in C
2.5 Python Datatypes v/s C datatypes
2.6 Type Checking C v/s Python
2.7 Summary
2.8 Unit End Questions
2.0 OBJECTIVES  Understanding variables and constants
 Understanding the concept of keyword and identifiers
 Working with datatypes and their conversion characters
 Comparing python and C datatypes
 C and python type checking
2.1 INTRODUCTION This chapter mainly focuses on the concept of variables, c onstants,
reserved keywords, identifiers and datatypes of C language. Variables are
nothing but names allocated to storage areas and are declared with the help
of datatypes. There are various categories of datatypes and these datatypes
are working with the help of their conversion characters. We will also
come to know how C and python datatypes are different form each other
and type checking in C as well as python.
2.2 KEYWORDS AND IDENTIFIERS Identifiers :
C identifiers are the names of variables, functio ns, arrays, structures,
unions, and labels in C program. An identifier is composed of uppercase,
lowercase letters, underscore, digits. Whereas starting letter should be
either an alphabet or an underscore. The identifiers are of two types i.e.
Internal id entifier and external identifier. If the identifier is not used in the
external linkage, then it is called as an internal identifier. If the identifier is
used in the external linkage, then it is called as an external identifier. munotes.in

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15 Programming With C Rules for constructing C identifiers :
1. The first character of an identifier should be either an alphabet or an
underscore and can be followed by character, digit or an underscore.
2. It must not begin with any digit
3. Commas and blank spaces are not allowed within the identifier
4. Keywor ds cannot be used as identifiers
5. The length of identifiers must not be more than 31 characters
Keywords :
Keywords are predefined reserved words which has special meaning
defined by the compiler. In C language there are 32 keywords as listed
below : auto double Int Struct break else long Switch case enum register Typedef char extern return Union continue for signed Void do if static While default goto sizeof Volatile const float short Unsigned
Literals :
Literals are the constant values assigned to t he constant variables. Literals
represent the fixed values which can not be modified. It contains memory
but does not have references as variables.
Types of Literals :



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16 Datatypes In C Integer literal :
It is a numeric literal that represents only integer type values. I t represents
the value neither in fractional nor exponential part.
An integer literal is suffixed by following two sign qualifiers:
L or l: It is a size qualifier that specifies the size of the integer type as
long.
U or u: It is a sign qualifier that repr esents the type of the integer as
unsigned. An unsigned qualifier contains only positive values.
Float literal :
It is a literal that contains only floating -point values or real numbers.
These real numbers contain the number of parts such as integer part, r eal
part, exponential part, and fractional part. The floating -point literal must
be specified either in decimal or in exponential form.
Decimal form :
The decimal form must contain either decimal point, exponential part, or
both. If it does not contain eith er of these, then the compiler will throw an
error. The decimal notation can be prefixed either by '+' or ' -' symbol that
specifies the positive and negative numbers.
Exponential Form :
The exponential form is useful when we want to represent the number,
which is having a big magnitude. It contains two parts, i.e., mantissa and
exponent. For example, the number is 2340000000000, and it can be
expressed as 2.34e12 in an exponential form.
2.3 VARIABLES AND CONSTANTS Variables:
The meaning of word variable enca psulated in it. If we segregate the word
Variable into two parts i.e. Vari (Vary) and Able it means capacity to
change. So the values of variables can be changed as and when required in
the program. Variables are the names given to the data storage areas used
for program manipulation . Each and every variable in C has its own
specific type and size, layout of memory allocation and range of values
that can be stored within that memory.
The rules regarding variable declaration are same as we have already see n
in rules for dec laration of identifiers such as:
1. Variable name must start with and alphabet only and can be followed
by digit and can have an underscore
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17 Programming With C 3. C language is case sensitive so same names of variabl es in uppercase
and lowercase will be treated as different.
Constants:
As we have seen the meaning of word variable is capacity to change and
hence we can state that value of the variable can be changes as and when it
is required in the program. However t he constants have the feature not to
changes its value anywhere in the program. It remains fixed in the whole
program.
The define a constant #define preprocessor can be used.
Eg : #define PI 3.14;
Here the constant PI is having value 3.14 and it cant be ch anged anywhere
in the program.
2.4 DATATYPES IN C


The above mentioned diagram reflects the datatypes in C. There are 4
categ ories of datatype and that are :
1. Basic: Basic datatypes are divided into two types :
a. Numeric : It contains the datatypes such as i nteger, float, long and
double
b. Non numeric : it contains single character and string


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18 Datatypes In C Following table illustrates the basic datatypes in depth : Sr. No Datatype Conversion Character Storage Size Declaration Method 1 Int %d 2 bytes Int a=10; 2 Float %f 4 bytes Float a=10.87; 3 Double %ld 8 bytes Double a=98.65 4 Char %c 1 byte Char a=’N’; 5 String %s As per the size Char a[10]=”Nisha”; Sr. No Datatype Conversion
Character Storage Size Declaration Method 1 Int %d 2 bytes Int a=10; 2 Float %f 4 bytes Float a=10.87; 3 Double %ld 8 bytes Double a=98.65 4 Char %c 1 byte Char a=’N’; 5 String %s As per the size Char a[10]=”Nisha”;
2 Derived : Derived datatypes include Arrays, pointer, structures, unions
and functions.
a. Arrays are group of similar datatype values stored in contiguous
memory locations sharing the same name. It can store primitive
datatypes such as int, char, double, float etc. Arrays also can store the
collection of derived datatypes such as structures, pointers etc. The
array is a simplest data structure where each of its element can be
accessed with the help of its index number.
b. A pointer is such a variable which stores address of another variable.
This variable can be of any type such as int, char, array, function or
any other pointer.
c. Structure is a user defined datatype which is like arrays only but the
main difference between structure and array is that structures can
store multiple values of different datatypes sharing same name. It can
be declared using the keyword struct. Structures are normally used to
represent records
d. Union is same as structure which allo ws to store multiple datatypes
but in same memory location. Union can be defined with many
members but one member can be accessed at a time. Union is an
efficient way to use same m emory location for multiple purpose.
2. Enumerated : These are the arithmetic types used to define variables
which can assign constant integer values throughout the program. It
makes the program easy to read and maintain. It can be defined using
keyword enum. Common examples are days or week i.e. Sunday, munotes.in

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19 Programming With C Monday,…. Saturday or compass directions such as North, South, East,
West etc.
3. Void : These are the types where no value is specified that means it is
empty datatype without a value. When we don’t want to retur n any
value to the calling function we use void keyword before the name of
that function.
2.5 PYTHON DATATYPES V/S C DATATYPES Python is a dynamically typed language so its not necessary to define type
of a variable while declaring. The interpreter impli citly binds the value
with its type.
Already we have seen datatypes in C language. However pyth on provides
following datatypes:


1. Numeric : In Python, numeric data type represent the data which has
numeric value. Numeric value can be integer, floating number or
even complex numbers. These values are defined as int, float and
complex class in Python.
a. Integers : This value is represented by int class. It contains positive
or negative whole numbers (without fraction or decimal). In Python
there is no lim it to how long an integer value can be.
b. Float : This value is represented by float class. It is a real number with
floating point representation. It is specified by a decimal point.
Optionally the character e or E followed by a positive or negative
intege r may be appended to specify scientific notation.
c. Complex Numbers : Complex number is represented by complex
class. It is specified as (real part) + (imaginary part) I for example -
2+3j
Note : Type() function is used to determine the type of data type:
2. Dictionary : Python’s dictionaries are kind of Hash table type. They
work like associative arrays or hashes found in perl and consist of
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20 Datatypes In C are usually numbers or strings values, on the other hand can be any
arbitrary Python object
3. Boolean : Python boolean type is one of the built -in data types
provided by Python, which represents one of the two values i.e. True
or False. Generally, it is used to represent the truth values of the
expressions. Fo r example, 1== 0 is True whereas2<1 is False. We
can evaluate values and variables using the Python bool() function.
This method is used to return or convert a value to a Boolean value
i.e., True or False, using the standard truth testing procedure.
4. Set: The collection of unique items that are not in order ae called as
sets. { } braces are used to define a set and , comma is used to
separate the set values. The items in set are unordered in nature.
Duplicate values are not allowed in sets. Operations li ke union and
intersection can be performed on two sets.
5. Sequence Type : In python sequence type can be categorized in 3
parts i.e. strings, list and tuple
a. Strings : A String is a sequence of Unicode characters. In Python,
String is called str. Strings are represented by using Double quotes or
single quotes. If the strings are multiple, then it can be denoted by the
use of triple quotes “”” or ”’. All the characters between the quotes
are items of the string. One can put as many as the character they
want w ith the only limitation being the memory resources of the
machine system. Deletion or Updation of a string is not allowed in
python programming language because it will cause an error. Thus,
the modification of strings is not supported in the python
progra mming language.
b. List: An ordered sequence of items is called List. It is a very flexible
data type in Python. There is no need for the value in the list to be of
the same data type. The List is the data type that is highly used data
type in Python. List da tatype is the most exclusive datatype in Python
for containing versatile data. It can easily hold different types of data
in Python. t is effortless to declare a list. The list is enclosed with
brackets and commas are used to separate the items.
c. Tupl e: A Tuple is a sequence of items that are in order, and it is not
possible to modify the Tuples. The main difference list and tuples are
that tuple is immutable, which means it cannot be altered. Tuples are
generally faster than the list data type in Pyth on because it cannot be
changed or modified like list datatype. The primary use of Tuples is to
write -protect data. Tuples can be represented by using parentheses (),
and commas are used to separate the items
2.6 TYPE CHECKING C V/S PYTHON Type checking is nothing but checking that each operation should receive
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21 Programming With C types of checking such as static type checking and dynamic type checking.
However Python uses dynamic type checking and C uses static type
checking
1. Static type checking : Static checking is done at complete time.
Information needed at compile time is provided by declaration by
language structures. The information includes
a. For each operation : The number, order, and data type of it s arguments
b. For each variables : Name and data type of data object
c. For each constant : Name, data type and value
Advantages:
a. Compiler saves information : If the type of data is according to the
operation then compiler saves that information for checking la ter
operations which further no need of compilation
b. Checked execution paths : As static type checking includes all
operations that appear in program statement, all possible execution
paths are checked and further testing for type error is not needed. So no
type tag on data objects on run time are not required and no dynamic
checking is needed.
Disadvantages:
a. Declarations
b. Data control structures
c. Provisions of compiling separately some subprograms
2. Dynamic type checking : Dynamic type checking is done at ru n time
and it uses concept of type tag which is stored in each data objects that
indicates the data type of the object
Advantages:
a. It is much flexible in designing programs
b. In this declarations are not required
c. In this type may be changed during execution
d. In this program are free form most concern about data type
Disadvantages:
c. Difficult to debug : We need to check program execution paths for
testing and in dynamic type checking, program execution path for an
operation is never checked.
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22 Datatypes In C e. Hardware Support : As hardware seldom support the dynamic type
checking so we have to implement in software which reduces execution
speed.
2.7 SUMMARY C identifiers are the names of variables, functions, arrays, structures,
unions, and labels.
Internal :
identifier and external identifier are the two types of indetifiers
Keywords are predefined reserved words which has special meaning
defined by the compiler.
Literals are the cons tant values assigned to the constant variables
variables have the capacity to change whereas constants remains fixed.
C language works with 4 different types of datatypes ie basic, derieved,
enumerated and void.
Type checking is nothing but checking that e ach operation should receive
proper number of arguments with proper data type
C uses static type checking and python uses dynamic type checking
2.8 UNIT END QUESTIONS 1. Explain keyword with its list
2. Write the difference between variable and constant
3. write sh ort note on c datatypes write the difference between static
type checking and dynamic type checking



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23
3
C VARIABLES
Unit Structure
3.0 Objectives
3.1 Introduction
3.2 Variable Declaration
3.3 Scope of Variables
3.4 Hierarchy Of Of Datatypes
3.5 Type of Declaration C V/S Python
3.6 Summary
3.7 Unit End Questions
3.0 OBJECTIVES  Understanding vari able and its scope
 How to use datatypes considering their hierarchy
 Getting knowledge about type of declaration in C and Python
3.1 INTRODUCTION A variable is simply something which is having the capacity to vary. Each
and every variable is having its own datatype. This datatype can either be
predefined or can be user defined. Specifically variables represent an
objects that can be measured, counted, controlled or manipulated.
However scope is that region or area of the program where the variables
can be ac cessed after its declaration.
3.2 VARIABLE DECLARATION In earlier chapter we have learnt that a variable is nothing but a storage
location in which values are stored. Each variable is having specific type
which determines the size and layout of the variab le’s memory. The names
of variables can be composed of letters, alphabets, digits, and an
underscore. Whereas uppercase and lowercase characters are considered
as different from each other as C is a case sensitive language.
Here we will see how the variabl es can be declared:
int a=10;
float b=20.30;
char c='T'; munotes.in

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24 C Variables double d=66.678;
char str[10]="nisha";
Here variables a,b,c,d and str are declared as well as defined with
datatypes such as int, float, char double and string and with values 10,
20.30, T, 66.678 an d nisha respectively.
A variable declaration provides the surety to the compiler that a variable is
in existence with a given type and name so that the compiler can proceed
for further compilation process without knowing the completer details of
the variab le. At the time of compilation process only the variable
definition gets its meaning which is required for linking of the program.
3.3 SCOPE OF VARIABLES These variables can be declared in one file and can be accessed in multiple
blocks, functions or file s just we need to define the scope of the variable.
To know the scope of variable first it is required to know where the
variable is exactly got stored. In this case storage classes play a vital role.
These storage classes in C are used to determine the v isibility, persistence,
initial value and memory location of a variable. There are 4 different types
of storage classes in C that are auto, extern, static and register. Following
diagram gives more clear picture about the storage classes.


1. Automatic: If we do not define any variable using any specific storage
class then by default it is automatic storage class. They are stored in
The scope and visibility of these types of variables is limited to the
block in which that variable is defined. The initial by default value can
not be predicted means it is a garbage value. The keyword used for
variable declaration is auto. munotes.in

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25 Programming With C Declaration method:


Output:


Here we c an see that value of variable a is a garbage value.
Now we will see scope of automatic type of variables with the help of
following example :


In this program initially the value of variable a is defined as 10. Whereas
the first printf statement will allow to print the value of a by incrementing
it by 1 and hence it will show the value of a as 11. Here is the scope of
variable a which we have declared as 10 is started. However in the next munotes.in

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26 C Variables line when we are writing int a=20 and then we are opening a for loop and
printing the value of a three times and then closing the for loop. In this
case the scope of variable a having value 20 will be in persistence within
the block of for loop only. As soon as we come out of for loop once again
the variable a will regain its original value as 11. So we will be able to see
the following output.
Output :


2. static : The variables which are declared with static storage class are
allowed to hold their values in multiple function calls. A static variable
can be declared multiple times but can be assigned with any value only
once. The values static local type of variables are accessible only in the
function or block in which they are defined. Whereas the values of
static global type of variables are accessible in the whole file in which
it is defined. The default initial value of integer type of variables is zero
and for other types it will be null.
Example:


In this program we have declared 3 different static global variables i.e. c, i,
f where c is a non numeric type of variable and i and f are numeric types
of variables. So whenever we will see their default initial v alue, for
numeric type it will be zero and for non numeric type it will be null.
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27 Programming With C Output :


The below example will illustrate the scope of variable and how it
holds the value in multiple function calls


In this program there are two functions i.e. sum( ) and the another one is
main(). Now in main() function we have called sum() function 3 times
using for() loop. However in the definition of function sum() we have
defined the initial values of variable a and b as 10 and 24 respectively. So
when we are sa ying that the function sum() is called 3 times in that case
for the first call of the sum() function the value of a and b will be printed
as 10 and 24 and will be incremented by 1. Now when the function sum()
is called second time, the incremented values o f a and b will be considered
as the static type of variables are having the capacity to hold the values
between different function calls and hence in the second iteration the
values of variables a and b will be printed as 11 and 25 and then these
values wi ll again be incremented by 1 and in the third iteration the values
of a and b will be printed as 12 and 26.
Output :

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28 C Variables 3. Extern : The external storage class tells the compiler that the variable
declared using extern are having external linkages elsewhere in the
program. These type of variables are global and cannot be initialized
within any block or function. They can be declared multiple times but
can be initialized only once. The default initial value of extern numeric
types of variables is zero and for non numeric types it is null. If a
variable is declared as external then the compiler searches for that
variable to be initialized somewhere in the program which may be
extern or static, but if it is not initialized then the compiler shows an
error.
Following examples will illustrate the working of extern types of
variables :
Example 1:


In the above example in the message section it is showing the error that a
is not defined because extern type of variables should be declared globally
i.e. outside the main() however in the given program we have declared it
inside the main() and hence compiler cant recognize the definition of
variable a anywhere.
Example 2 :
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29 Programming With C Now here since the variable a is declared outside the main() it will be
recognized and since the variab le a is of integer type it will show its
default value as 0
Output:


Example 3:


In this example we are trying to initialize the variable a with value 20
inside the main() which is not valid and hence it will show the error that
extern variable can n ot be initialized.
Example 4:
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30 C Variables In this program the variable a is declared globally with value 10 and will
print the value as 10.
Example 5 :


However when we will compare example no 4 and example no 5 we can
see that when we want to define variable a wit h value 20 after main()
function it is showing us an error as extern types of variables can not be
defined multiple times.
4. Register: We have seen all the other types of variables i.e. auto, static
and extern are getting stored in computer’s memory whereas the
variable declared with register used to get store in cpu register
depending upon the size of the memory remaining in the CPU. These
types of variables cannot be dereferenced means we can not use &
(address operator) for such type of variables. Since th ese types of
variables are stored in CPU register their access time is faster. The
keyword register is used to store the variable in CPU register however
its compiler’s choice whether to store then in register or not. The
default initial value of register variables is a garbage value
Following example will illustrate the working of register types of
variables:
Example 1:
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31 Programming With C In this program it will show the garbage value of a.
Output:


3.4 HIERARCHY OF DATATYPES Already we have seen the topic datatype i n earlier chapter. C provides 4
basic categories of datatypes such as basic, derived, enumeration and void.
However the hierarchy of these datatypes can be explained with the help
of following diagram .


The hierarchy of primary datatypes will be as follo ws:
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32 C Variables Following table will help us to understand more about all the above
mentioned datatypes :
Data type Memory Size Range Char 1 byte −128 to 127 signed char 1 byte −128 to 127 unsigned char 1 byte 0 to 255 Short 2 byte −32,768 to 32,767 signed short 2 byte −32,768 to 32,767 unsigned short 2 byte 0 to 65,535 Int 2 byte −32,768 to 32,767 signed int 2 byte −32,768 to 32,767 unsigned int 2 byte 0 to 65,535 short int 2 byte −32,768 to 32,767 signed short int 2 byte −32,768 to 32,767 unsigned short int 2 byte 0 to 65,535 long int 4 byte -2,147,483,648 to 2,147,483,647 signed long int 4 byte -2,147,483,648 to 2,147,483,647 unsigned long int 4 byte 0 to 4,294,967,295 Float 4 byte Double 8 byte long double 10 byte
3.5 TYPE OF DECLARATION C V /S PYTHON Type declaration in C:
Type definition is a feature of C programming language which allows a
programmer to define an identifier which represents existing data types of
a variable. The user defined identifier can be used later in the program to
declare variables.
Syntax :
typedef type identifier; Here, type is an existing data type and identifier is the name given to the
data type.
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33 Programming With C Example:
typedef int age; typedef float weight; Here we can observe that age represents integer type of data and we ight
represents float type of data.
age boy1,boy2; weight b1,b2; Here, boy1 and boy2 are declared as as integer data type and b1 & b2 are
declared as floating integer data type.
The main advantage of using user -defined type declaration is that we can
create meaningful data type names for increasing the readability of a
program.
Another user -defined data type is enumerated data type. The general
syntax of enumerated data type is:
enum identifier {value 1,value 2,...value n}; Here, identifier is a user -defined enumerated data type which can be used
to declare variables that can have one of the values enclosed within the
braces. The values inside the braces are known as enumeration constants.
After this declaration, we can declare variables to be of this ‘new ’ type as:
enum identifier v1, v2, ... vn; The enumerated variables v1, v2, … vn can only have one of the values
value1, value2, … valuen. The following kinds of declarations are valid:
v1=value5; v3=value1; User -defined Type Declaration Example :
enum mnth {January, February, ..., December}; enum mnth day_st, day_end; day_st = January; day_end = December; if (day_st == February) day_end = November;
The compiler automatically assigns integer digits begriming with 0 to all
the enumeration constants. That is, the enumeration constant value1 is
assigned 0, value2 is assigned 1, and so on. However, the automatic
assignments can be overridden by assigning values explicitly to thee
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34 C Variables For example:
enum mnth {January = 1, February, ..., December }; Here, the constant January is assigned value 1. The remaining values are
assigned values that increase successively by 1.
The definition and declaration of enumerated variables can be combined in
one statement. For example;
enum mnth {January, ... Decem ber} day_st, day_end; Type declaration in Python :
Now we all know that in C variables can be declared as:
Int x,y,z; Whereas in python it can be declared as :
X=0 Y=0 Z=0
In python types of variables and functions can be declared in following
way
explicit _number: type or,
def function(explicit_number: type) -> type: pass
Following example will illustarate how to use static type checking in
python :
from typing import Dict def get_first_name(full_name: str) -> str: return full_name.split(" ")[0] fallback_name: Dict[str, str] = { "first_name": "UserFirstName", "last_name": "UserLastName" } raw_name: str = input("Please enter your name: ")
first_name: str = get_first_name(raw_name) # If the user didn't type anything in, use the fallback name if not first_name: first_name = get_first_name(fallback_name) print(f"Hi, {first_name}!") munotes.in

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35 Programming With C 3.6 SUMMARY A variable is simply something which is having the capacity to vary and it
represents an objects that can be measured, counted, controlled or
manipulated.
A variable declaration provides the surety to the compiler that a variable is
in existence with a given type and name
Storage classes allows to understand the scope of variables
There are 4 types of storage classes such as auto, static, exter n and
register.
C datatypes work with a specific hierarchy and includes primitive
datatypes, compound datatypes, library datatypes and user defined
datatypes
3.7 UNIT END QUESTIONS 1. Write short note on variables
2. Explain datatypes in c in detail
3. Explain hie rarchy of datatypes in c
4. Write the difference between type checking in c and python
Book References
Let us C – Yashwant P Kanetkar – BPB Publication
Web References
https://www.javatpoint.com/data -types-in-c
https://www.tutorialspoint.com/cprogramming/index.htm


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36
4
TYPES OF OPERATORS
Unit Structure
4.0 Objectives
4.1 Types Of Operators
4.2 Precedence & Order Of Evaluation
4.3 Statement & Expressions
4.4 Automatic & Explicit Type Conversion
4.5 Miscellaneous Programs
4.6 Summary
4.7 Unit End Questions
4.0 OBJECTIVES This chapter would make you understand the following concepts :
 To design programs to perform basic calculations .
 To compare two entity and implement decision making order of
evaluation of operators .
4.1 TYPES OF OPERATORS C Programming lan guage supports a set of built -in operators. An operator
is a symbol that operates on the operands and instructs the compiler to
perform certain operations. Operands can be any variables that hold value.
The various types of Operators are as follows:
1. Arith metic Operator
2. Relational Operator
3. Logical Operator
4. Compound Assignment Operator
5. Increment/Decrement Operator
6. Conditional & ternary Operator
7. Bitwise & comma operator
4.1.1 Arithmetic Operator:
This operator supports performing basic mathematical operations .
Following are the operators used for arithmetic operations:
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37 Programming With C Symbol Description Example Assume a=10 and b=5 + Addition of two operand values a+b Output: 15 - Subtraction of two operand values a-b Output: 5 * Multiplication of two operand values a*b Output: 50 / Division (Quotient) of two operand values a/b Output: 2 % Modulus (Remainder) of two operand values a%b Output: 0 (Since a is divisible by b)
Example:
Program to calculate Simple Interest
#include
void main()
{
int p, n;
float rat e, Simple_interest;
p=10000;
n=10;
r=5.5;
Simple_interest = (p* n * r)/100;
printf(“Simple Interest = %f”,Simple_interest);
getch();
}
4.1.2 Relational Operator:
Relational operator is also known as Comparison operator. It performs
comparison between tw o operand values :
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38 Types Of Operators Operator Description Example Assume a=10 and b=5 == Check if two operand values are equal a==b Output: false != Checks if two operands values are not equal a!=b Output: true > Checks if left operand value is greater than right operand value a>b Output: true < Checks if left operand value is smaller than right operand value a= checks if left operand value is greater than or equal to right operand value a>=b Output: true <= Check if left operand value is smaller than or equal to right operand value a<=b Output: false
Example:
#include
void main()
{
int a, b;
a=10;
b=20;
printf(“Value = %d”, a<=b);
printf(“Value = %d”, a==b);
printf(“Value = %d”, a>b);
printf(“Value = %d”, a!=b);
getch();
}
Output :
Value = 1
Value = 0
Value = 0
Value = 1 munotes.in