C programming .pptx

1
Programming
in
C
Presented by:
Suhaib Rehman
Trainer

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Introduction to ProblemSolving

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Stages of Problem solving
“Computer programmers are problem solvers”
Problem-Solving: It is the act of identifying the problems and implementing the best possible
solutions.
It is the job of the programmer to write down the solution
To solve a problem with one needs to pass through certain stages/steps.
Steps in Problem-Solving:
•Identify the problem
•Define the context of the problem
•Explore possible strategies
•Act on the best solution
•Coding and implementation.
•Look back and learn

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•Identify the problem
Define Problem
The first step in solving a problem is understanding what that problem actually is. You need
to be sure that you're dealing with the real problem.
To really solve the problem, it's important to find out what started it all. This is called
identifying the root cause
However, defining a problem doesn't mean deciding how to solve it straight away. It's
important to look at the issue from a variety of perspectives. If you commit yourself too early,
you can end up with a short-sighted solution
As you define your problem, you'll often discover just how complicated it is.
•Define the context of the problem

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Problem-solving steps
A.Use of specific Example:
Focusing on a particular problem can give us the foothold we need for making a start on
the solution to the general problem.
B. Similarities among problems:
 Check similarities between the current problem and past problems which we have solved
 more experience one has with tools and techniques, more efficiently he/she can tackle the given
problem.
 But sometimes it blocks us from discovering a desirable or better solution to the
problem
C. Working backward from the solution:
We have a solution to a problem and then try to work backward to the starting point.
The “Work Backward” method works well for problems where a series of operations is done on an
unknown number and you’re only given the result.
Explore the strategies

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Problem-solving steps
Working backward from the solution: Example
Sam’s mom left a plate of cookies on the counter. Sam ate 2 of them, his dad ate 3 of them and they
gave 12 to the neighbor. At the end of the day, only 4 cookies were left on the plate. How many cookies
did she make altogether?

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General Problem solving Strategies
Problem-solving strategies don’t guarantee a solution, but they do help guide you through the process
of finding a resolution.
Often we phrase a problem in one of the following strategies:
1. trial and error. In other words, you try different solutions until you find one that works.
2. Divide and Conquer: E.g Merge Sort

Representation of Algorithm
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Flow chart Pseudocode

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Coding and implementation.
A flowchart is a diagram that depicts a process, system or computer algorithm. They are widely
used in multiple fields to document, study, plan, improve and communicate often complex processes in
clear, easy-to-understand diagrams
Start/End Symbol
The terminator
symbol marks the
starting or ending
point of the
system. It usually
contains the word
"Start" or "End."
Action or Process
Symbol
A box can represent a
single step ("add two
cups of flour"), or an
entire sub-process
("make bread") within a
larger process.
Document
Symbol
A printed
document or
report
Multiple
Documents
Symbol
Represents
multiple
documents in
the process
Decision Symbol
A decision or branching
point. Lines representing
different decisions
emerge from different
points of the diamond.

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Input/Output Symbol
Represents material or
information entering or
or leaving the system,
such as customer order
order (input) or a
product (output).
Preparation Symbol
Represents a set-up to
another step in the
process.
Connector Symbol
Indicates that the flow
continues where a
matching symbol
(containing the same
letter) has been placed
Delay Symbol
Indicates a delay in the
process.
Database Symbol
Indicates a list of information with a standard
structure that allows for searching and sorting
Display Symbol
Indicates a step that
displays informatio

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What is an Algorithm?
A sequence of steps to solve a given problem is called as algorithm. Thus, an algorithm
is a step-by-step procedure developed for solving a given problem. An algorithm consists
of sequences, iterations, selections, etc
What is a Pseudocode?
Pseudocode is an informal method of developing an algorithm. Thus, computer programmers
use simple informal language to write a pseudocode. It does not have any specific syntax to
follow.
The main difference between an algorithm and a pseudocode is that an algorithm is a step-by-step
procedure to solve a given problem while a pseudocode is a method of writing an algorithm.
Yes, algorithms can be known as pseudocodes. They are sometimes considered as pseudocodes.
Whereas pseudocodes can not be considered as algorithms as they might not carry exact information
required to carryout the solution to the problem

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1. Start from the leftmost element of arr[] and one by one compare x with
each element of arr[].
2. 2. If x matches with an element, return the index.
3. 3. If x doesn’t match with any of elements, return -1.
Algorithm of linear search
Pseudocode for Linear Search :
FUNCTION linearSearch(list, searchTerm):
FOR index FROM 0 -> length(list):
IF list[index] == searchTerm THEN
RETURN index
ENDIF
ENDLOOP
RETURN -1
END FUNCTION
In here, we haven’t used any specific programming language but wrote the steps
of a linear search in a simpler form which can be further modified into a proper
program

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Algorithm vs Pseudocode vs Program:
1.An algorithm is defined as a well-defined sequence of steps that provides a
solution for a given problem, whereas a pseudocode is one of the methods that
can be used to represent an algorithm.
2.While algorithms are generally written in a natural language or plain English
language, pseudocode is written in a format that is similar to the structure of a
high-level programming language. Program on the other hand allows us to
write a code in a particular programming language.

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Test and
Debug
Debugging •Debugging: Debugging is the process of finding and resolving
defects or problems within a computer program that prevent correct
operation of computer software or a system. •

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Programming errors
Syntax errors
:
•misspelling a statement, eg writing prit instead of print
•using a variable before it has been declared
•missing brackets, eg opening a bracket, but not closing it
Logic errors
• A logic error is an error in the way a program works. The
program can run but does not do what it is expected to do.
• unintentionally creating a situation where an infinite loop may
occur
Runtime errors
A runtime error is an error that takes place during the running of
a program.
An example is writing a program that tries to access the sixth item
in an array that only contains five items. A runtime error is likely
to crash the program.

What is a programming language? 21
To communicate with a person, we need a specific
language.
Language is a mode of communication that is used
to share ideas, opinions with each other.
Language?
A programming language is a computer language that is used to
communicate with computers..
Programming Language?

What is a programming language? 22
A programming language is used to develop software programs,
or
A programming language contains sets of instructions for computers to execute.
A programming language is mainly used to develop desktop applications, websites, and
mobile applications, system programs etc.

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Types of programming language
Low level
programming language
Assembly
Language
Machine
Language
High level
programming language
Procedural
Oriented
programming
language
Object Oriented
Programming
Language
C C++ Java PHP Android Java script Python

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Machine code or object code: Computers directly understand the machine language
program.
The lowest level of software is machine code.
Other programming languages are converted to machine code before being executed
by the computer.
Machine code consists of the CPU’s directly comprehensible binary instructions.
Binary is the most common format.
Machine Code
For example, take ASCII, the ‘01000001’ bit pattern represents the ‘A’ letter.
ASCII, abbreviated from American Standard Code for Information Interchange: Character encoding standard
for electronic communication.

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The assembler language is the symbolic programming language that lies close to the
machine language in form and content. The assembler language is useful when:
->You need to control your program closely, down to the byte and even the bit level.
->Assembly Language is expressed in a more human readable form than the binary instructions
Assembly Language
.
MOV A,[1]
MOV B,[2]
ADD A,B
MULT A,B

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High-level programming language (HLL) is designed for developing user-friendly
software programs and websites.
This programming language requires a compiler or interpreter to translate the
program into machine language (execute the program).
Example: Python, Java, JavaScript, PHP, C#,
High level Programming Language

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Middle-level programming language lies between the low-level programming
language and high-level programming language.
It is also known as the intermediate programming language or pseudo-language.
A middle-level programming language's advantages are that it supports the features of
high-level programming i.e. it is a user-friendly language, and closely related to
machine language and human language.
Example: C language
Middle-level programming
language
C programming supports Inline assembly language programs. We can directly access
system registers with the help of inline assembly language feature in C.
C programming is used to access memory directly using a pointer.
The actual Linux kernel code is only in C and Assembly.

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History of C
Date Language
1960 ALGOL International group
1967 BCPL Martin Richards
1970 B Ken Thompson
1972 TRADITIONAL C Dennis Ritchie at Bell Laboratories
1978 K&R C Kernighan and Ritchie
1989 ANSI C ANSI Committee
1990 ANSI/ISO C ISO Committee
1999 C99 Standardization Committee

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ALGOL: Algorithmic Language
BCPL:Basic Combined Programming Language.
C: become more popular after the publication of the book “ The C Programming
Language” by Kernighan and Dennis Ritchie in 1978. and language was known as K&R
C.
Growth of C led to development of different version of the language that were similar but
often incompatible.
To assure that C remains standard, in 1983, American National Standards Institute(ANSI)
appointed a technical committee to define standard for C.
IT was then approved by the International Standards Organization(ISO) in 1990.
C++ and Java were evolved out of C, and then few features of C++ and Java were added
to C. This version is usually referred to as C99.
History of C

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Features of C
It is machine independent
A function can
call itself again
and again
until certain
criteria is met
Pointers are memory variables which
stores the address of another variable
instead of storing a value.
It easily manages memory during
runtime And during compile time.
It is easy to learn
It can be extended
easily to add new
features
Libraries include
number of pre-
defined functions
which can be used
directly in a
program
It’s syntax is similar to
machine
language as well as
human
language
It follows a block structured approach
in which set similar statements are written
inside two curly brackets { }
FEATURES OF C LANGUAGE

 C language is used for creating computer applications
 Used in writing Embedded software
 Firmware for various electronics, industrial and communications products which use micro-controllers.
 It is also used in developing verification software, test code, simulators etc. for various applications and hardware products.
 For Creating Compiler of different Languages which can take input from other language and convert it into lower level machine
dependent language.
 C is used to implement different Operating System Operations.
 VLC media player is an open-source software and a cross-platform media player and streaming media server. This application
is written using a combination of C, C++ and Objective – C programming languages.
 Microsoft Office Suit- Originally written in C programming language, most of it’s portion is now switched on to C++ programming
language for the object oriented programming paradigm shift.
 Adobe has rolled out some of the world-class products in animation domain. We have some amazing tools that have been
developed in C programming language such as Adobe Photoshop, Adobe Illustrator, Adobe Premier, Adobe Image Ready and
others.
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REAL WORLD APPLICATIONS OF C PROGRAMING LANGUAGE

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Structure of C program is defined by set of rules called
protocol, to be followed by programmer while writing C
program. All C programs are having sections/parts which
are mentioned below.
suitor
1. Documentation section
2. Link Section
3. Definition Section
4. Global declaration section
5. Function prototype/ declaration section
6. Main function
7. User defined function definition section
Structure OF C Program

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Structure OF C Program
Documentation Section: consists of set of comment lines, name of program, author and other details
Link Section: provides instructions to the compiler to link functions from the system library.
Definition Section: defines all symbolic constants.
Global Declaration section: Variable that are declare in the global declaration section that can be
accessed to all functions. This section also declares all the user-defined functions.
Main function: Every program must have one main() function section. This section also contains two
parts, declaration part and executable part. All the statements in the declaration and executable part end
with a semicolon ;
Subprogram section: contains all the user defined functions and are called in main function
Note: All sections , except the main function section may be absent when they are not required

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Creating the Program
Windows
Integrated development environment Software
•Save the file with “.c” extension.
•Open cmd and write “gcc first.c -o first.exe”
command.
•To execute, enter first
•Here “first.c” is the source code file name and
first.exe is the name of the exe file that the
compiler will create.
•Save the file with “.c” extension.
•Cc first.c
•The compiled and linked program is called executable object
code and is stored automatically file named a.out.
•To execute, enter command a.out
• create your own executable file:
cc –o name source-file
If you are using text
editor then install
GCC compiler first.
Add bin path to
system path
-check installed or
not enter gcc -v

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Character Set
Character set:- The character set is the fundamental raw material of any language and they are used
to represent information. These characters are used to form words, numbers and expressions.
Like natural languages, computer language will also have well defined character set, which is useful to
build the programs.

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ALPHABETS
Uppercase letters A-Z
Lowercase letters a-z
DIGITS 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
SPECIAL CHARACTERS
~ tilde % percent sign | vertical bar @ at symbol + plus sign < less than
_ underscore - minus sign > greater than ^ caret # number sign = equal to
& ampersand $ dollar sign / slash ( left parenthesis * asterisk back slash
) right parenthesis ′ apostrophe : colon [ left bracket " quotation mark ; semicolon
] right bracket ! exclamation mark , comma { left flower brace ? Question mark . dot operator
} right flower brace
WHITESPACE CHARACTERS
b blank space t horizontal tab v vertical tab r carriage return f form feed n new line
Back slash ’ Single quote " Double quote ? Question mark 0 Null a Alarm (bell)
Character Set
The characters in C are grouped into the following :

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C Token
Smallest individual units are known as tokens.
E.G in a passage of text, individual words and punctuation marks are called tokens
C programs are written using these tokens and the syntax of the language
C Tokens
Keywords Constants Strings Operators
Identifiers Special Symbols
Float
while
-15.5
100 “ABC”
+ -
amount [], {}

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Keywords: have fixed meaning and cannot be changed.
Identifiers: User-defined names (names of variables, functions, arrays)
Keywords and Identifiers
Keywords in C Programming
auto break case char
const continue default do
double else enum extern
float for goto if
int long register return
short signed sizeof static
struct switch typedef union
unsigned void volatile while
Rules of Identifiers:
 First character must be an alphabet or
underscore.
 Must consists of only letters, digits or underscore
 Cannot use a keyword
 Must not contain white space

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Constant in C refers to fixed value that do not change during the execution of a program
Constants
Numeric Constants Character Constants
Integer Constants
Real constants
Single character
Constants
String Constants
Constants
Integer Constants: Refers to sequence of digits E.g. 123
->decimal integer 0-9
-> octal integers 0-7 with leading 0 e.g. 037 0435
-> hex decimal integers 0-9, A-F. e.g. 0X9F
Note: embedded spaces, commas, and non-digit characters are not permitted. E.G. 20,000

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Real constants
Real Constants: Quantities that contain fractional parts like 17.34. Such numbers are called real or
floating point constants.
Note: Integers are inadequate to represent quantities that vary continuously such as distance ,
height ,temperature .
A real number may also be expressed in exponential (or scientific notation).
E.G. 215.45 may be written as 2.1545e2 where e2 means multiple by 102
Single character constants String constants
Character constant contains characters
closed within a pair of single quote
E.G ‘5’, ‘X’
String Constant is a sequence of
characters enclosed in double quotes
E.G “Hello”
Character constants

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Variables
A variable is a data name that may be used to store a data value.
A variable may take different values a different times during execution.
ANSI (American National Standards Institute) standard recognizes a length of 31
characters. However the length should not be more than eight characters, since only
the first eight are treated as significant by many compilers.
In c99 , at least 63 characters are significant.
-remember Abc is not same as abc
First_tag valid
Char invalid (keyword)
Prices$ invalid (Dollar sign is illegal)
Com sci  invalid (blank space)

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Data types
C language is rich in its data types.
Data type specifies the type of data that the variable can store like integer, character, floating,
double, etc.
Each variable in C has an associated data type.
Each data type requires different amounts of memory and has some specific operations which
can be performed over it.
C99 adds three more data types :- _Bool, _complex and imaginary

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Primitive/Fundamental data type: Each data type requires different amounts of
memory and has some specific operations which can be performed over it.
Derived data type : These data types are defined by user itself. User specifies the
amount of space it is going to take and the type of operation .
Derived data types are created from basic data types such as int, float, char, etc.
User Defined Data type: the programmer can invent his/her own data types in C
programming.
it is called a user-defined data type is that the variables of different types are clubbed together under a
single structure user-Defined

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Procedures for Binary Subtraction by 1’s Complement
•Write the 1’s complement of the subtrahend  change 0 to 1 and vice varsa.
•Then add the 1’s complement subtrahend with the minuend
•If the result has a carryover, then add that carry over in the least significant bit
•If there is no carryover, then take the 1’s complement of the resultant, and it is negative.
10-5 =5
Binary of 10= 1010
Binary of 5=0101
1010
- 0101
+ 101
5-10 =-5
Binary of 5= 0101
Binary of 10=1010
0101
- 1010
--------
1’s compliment of 10(subtrahend) = 1010 0101 add
this to binary of 5(minuend) 0101
5 0101
100101
+______
1010 no carry take 1’s compliment of result
and it is negative 0101 -5
Whenever a number with minus
sign is encountered, the number
(ignoring minus sign) is converted
to its binary equivalent. Then the
two’s complement of the number
is calculated. That two’s
complement is kept at place
allocated in memory and the sign
bit will be set to 1 because the
binary being kept is of a negative
number. Whenever it comes on
accessing that value firstly the
sign bit will be checked if the sign
bit is 1 then the binary will be
two’s complemented and
converted to equivalent decimal
number and will be represented

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Type Storage size Value range
char 1 byte -128 to 127 or 0 to 255
unsigned char 1 byte 0 to 255
signed char 1 byte -128 to 127
int 2 or 4 bytes -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
unsigned int 2 or 4 bytes 0 to 65,535 or 0 to 4,294,967,295
short 2 bytes -32,768 to 32,767
unsigned short 2 bytes 0 to 65,535
long 8 bytes or (4bytes
for 32 bit OS)
-9223372036854775808 to 9223372036854775807
unsigned long 8 bytes 0 to 18446744073709551615
Primary Data types

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Type Storage size Value range Precision
float 4 byte 1.2E-38 to 3.4E+38 6 decimal places
double 8 byte 2.3E-308 to 1.7E+308 15 decimal places
long double 10 byte 3.4E-4932 to 1.1E+4932 19 decimal places
Floating-Point Types
Data types

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Character Types
Void Types
Characters are usually stored in 8bits.
The qualifier signed and unsigned may explicitly applied to char
The void type has no values.
Usually used to specify the type of function.
A function is said to be void when it doesn’t return any value to the calling function
Data types

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Data type Variable_Name =constant;
Int a=100;
Char b=‘x’;
Float =75.8
The process of giving initial values to variables is called initialization.
C permits initialization of more than one variable in one statement using multiple
assignment operator E.G. a=b=c=0;
Assigning values to variables

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scanf() function
Another way of assigning values to variables is to input data from keyboard using scanf funtion
1.scanf(“control string",&variable1, &variable 2……);
The format string can be %d (integer), %c (character), %s (string), %f (float) etc.
Printing data to console
printf() function
The printf() function is used for output. It prints the given statement to the console.
The syntax of printf() function is given below:
1.printf("format string",argument_list);
The format string can be %d (integer), %c (character), %s (string), %f (float) ,%.12lf( long float to 12
decimals) etc.
Reading data from Keyboard
printf() function
The printf() function is used for output. It prints the given statement to the console.
The syntax of printf() function is given below:
1.printf("format string",argument_list);
The format string can be %d (integer), %c (character), %s (string), %f (float) ,%.12lf( long float to 12
decimals) etc.

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Type Size (bytes) Format Specifier
int at least 2, usually 4 %d, %i
char 1 %c
float 4 %f
double 8 %lf
short int 2 usually %hd
unsigned int at least 2, usually 4 %u
long int at least 4, usually 8 %ld, %li
long long int at least 8 %lld, %lli
unsigned long int at least 4 %lu
unsigned long long
int
at least 8 %llu
signed char 1 %c
unsigned char 1 %c
long double at least 10, usually 12 or 16 %Lf

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Interpreter
Language Translators
1. Scans whole program in one go
2. Errors are shown in one go
3. It does not require source code for later
execution.
4. IT takes a large amount of time for
analyzing the source code
5. Object code is generated
6. Programming languages like C, C++,
Java use compilers.
7. Compiler is based on translation
linking-loading model,
8. A linker program that takes the object
files, produced by compiler, join them
into a single executable file.
9. It is special program that takes input of
executable files from linker, loads it to
main memory, and prepares this code
for execution by computer
1. It translates only one statement of the
program at a time.
2. Errors are shown line by line.
3. It require source code for later
execution.
4. Interpreters take less time for analyzing
the source code.
5. No object code is generated
6. Debugging is easy
Programming languages like JavaScript,
Python,PHP Ruby use interpreters.
Compiler

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The compilation process in C involves four steps: pre-processing,
compiling, assembling, and linking.
All the statements starting with the # symbol in a C program are processed by the pre-processor,
and it converts our program file into an intermediate file with no # statements
Pre processing
Source Program
Expanded source
code
Assembly code Object code
Preprocessing Compiling
Linking
Exe code
assembling
first.i abc.s
first.c abc.obj/abc.o
abc.exe/abc.out

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System Ready
Enter program
Program Code
Edit Source program
C compiler
Syntax
Error
Link with system Library
Execute object code
Logic and
Data
Errors
Correct Output
Compile Source Program
System Library
Input Data
Stop
No errors
Logic errors
Data error
No
Source Program
Yes
Object Code
Executable object code
Process of compiling and running a C Program

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Comments in C
Single-line comments start with two forward slashes (//).
Multi-line comments start with /* and ends with */.
Let us play with char data type

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you must use the char type and create an array
Strings are used for storing text/characters
String in C
C does not have a String type to create string variables
char university[] = “chitkara";
printf("%c", university[0]);
char university[] = “chitkara";
printf("%s", university);

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String in C
Take Input of a String in C Without Spaces
The scanf() function is probably the easiest way to string input in C. We just need the access
specifier %s
Hence, the scanf() function should be preferred when we know the string we want to input doesn't
contain white spaces and that it will not exceed the memory buffer.
gets() function
The working of gets() is such that it keeps reading the input stream until it encounters a
newline character: n. Hence, even if the string input in C has spaces in it, all of them get
included as input until n doesn't occur.
But gets() doesn't care about the size of the character array passed to it and would lead to buffer over
flow
A buffer overflow (or buffer overrun) occurs when the
volume of data exceeds the storage capacity of the
memory buffer The gets() method is no longer a standard
function according to the C11 standard ISO/IEC
9899:2011. But it is still available in libraries
and will continue to be available for
compatibility reasons.

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String in C
Take Input of a String in C With
Spaces
fgets() can take string input in C from both the standard input stream or from
some file
fgets(char_array, size, stdin);
1.{%[^n]%*c} inside scanf
•%*[^n] scans everything until a n, but doesn't scan in
the n. The asterisk(*) tells it to discard whatever was
scanned.
•%*c scans a single character, which will be the n left
over by %*[^n] in this case. The asterisk
instructs scanf to discard the scanned character.
In scanf function you can use regular expressions to
restrict or validate the char you are going to read, here in
your question [^n] is regular expression that will
exclude n i.e in other words scanf will read all char until
you hit enter button.
Now coming to %*c , * is used to indicate don’t assign

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#include <stdio.h>
int main() {
int i = 10;
char c = 'a';
int add;
add= i + c;
printf("Value of sum : %dn", add );
}
Integer promotion:
C is converted in ascii
int main() {
char i = '1';
char c = 'a';
int add;
add= i + c;
printf("Value of sum : %dn", add );
}

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Type Casting in C
Converting the value of one data type to another type is known as type conversion.
C permits the mixing of constants and variables of different types in an expression.
C automatically converts any intermediate values to the proper type without losing any
significance._________IMPLICIT TYPE CONVERSION.
RULE: Lower type is converted into a higher type
All short and char are converted to int.
I. if one operand is long double the other will be converted long double.
II. If one operand is double the other is converted to double and result will be double.
III. --------------------float the ----------------------float and -----------------float.
IV. ---------------------long int----------------------long int and --------------long int.
The final result of an expression is converted to type of variable on the left of
assignment sign before assigning value to it.
Following changes are introduced
Float to int cause truncation of fractional part.
Double to float cause loss of rounding digits.
Long int to int cause dropping of excess higher order bits

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x= 1/i + i*f - d
int Float
int i,x;
float f;
double d;
long int 1;
int double
long
long
long float Float
int
double
int
float
float
double
An expression is a combination of operators and
operands which reduces to a single value.

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Type Casting in C
EXPLICIT TYPE CONVERSION:
When we want to force type conversion.
Ratio =quantity1/quantity2;
If quantity1 and quantity2 are declare integers then decimal part of the result would be
lost.
Ratio=(float)qualtity1/quantity2
The operator (float) converts the quantity1 number to floating point for the evaluation.
The type of quantity1 remains as int in other parts of the program.
Z=(int)3.4;
A=(int)21.3/(int)4.5

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Operators and Expressions
Operators: Operators are used in programs to manipulate data and variables.
C operators are classified into a number of categories:
1. Arithmetic operators
2. Relational operators
3. Logical operators
4. Assignment operators
5. Increment and decrement operators
6. Conditional operators
7. Bitwise operators
8. Special operators
An expression is sequence of operators and operands that reduces to
a single value. E.G 10+15;

65
Operators
Operator Meaning
+ Addition or unary plus
- Subtraction or unary minus
* Multiplication
/ Division
% Modulo Division
Operator Meaning
< Is less than
<= Is less than or equal to
> Is greater than
>= Is greater than or equal to
== Is equal to
!= Is not equal to
Arithmetic operators
Relation operators
Relational operators help
in making a relationship or
comparison between two
operands with which they
are used
An arithmetic operator is
used to perform
arithmetic/mathematical
operations on operands.

66
Operators
Operator Meaning
&& Logical AND
|| Logical OR
! Logical NOT
Operator Meaning
Syntax: V op=exp
V=variable, op= operator, exp=expression
a=a+1 a+=1
a=a-1 a-=1
a=a*(n+1) a*=n+1
a=a/(n+1) a/=n+1
a=a%b a%=b
Logical operators (used to test more than one condition)
Assignment Operators( used to assign the result of an expression to a variable)
The logical operators are
used when we want to
check or test more than
one condition and make
decisions.
An assignment operator is
used to assign values to
the operands.

67
Operators
Operator Meaning
++ ++ adds 1 to the operand
- - -- subtracts 1 from the operand
Postfix(a++) and prefix(++a)
a++(postfix) and ++a(prefix) mean the same thing but they form the
statements independently, they behave differently.
 Increment and decrement operators are unary operators.
 a=5 a=5
 b=++m b=a++
Increment and Decrement operators
Unary operators: are
operators that act upon a
single operand to produce a
new value.
Types of unary operators:
1.unary minus(-)
2.increment(++)
3.decrement(- -)
4.NOT(!)
5.Addressof operator(&)
6.sizeof()
The minus operator changes the sign of its argument. A positive number becomes negative, and a negative
number becomes positive.
unary minus is different from the subtraction operator, as subtraction requires two operands.

68
Operator Meaning
For manipulating data at bit level.
 Bitwise operators are not applied to float or double
& Bitwise AND
| Bitwise OR
^ Bitwise Exclusive OR
<< shift left
>> Shift right
Bitwise Operators
Conditional Operators
Operator Meaning
Exp1? Exp2:exp3
Exp1 is evaluated first, if it is nonzero (true) then exp2 is evaluated otherwise
exp3 is evaluated
Operators

69
Operator Meaning
,
Used to link the related
expressions together
Comma
& Address Operator
sizeof() sizeof
Special Operators
Operators
int main() {
int value;
int x,y;
value = (x=10, y=5);
printf("%d %d",x,y);
return 0;

70
Arithmetic Expression
Operator Description Associativity Rank
() Left to right 1
+,-,++,--
,!,~,*,&
sizeof(),
Right to Left 2
*,/,% Left to right 3
+ - Left to right 4
<< ,>> Left to right 5
<,<=,>,>= Left to right 6
==, != Left to right 7

71
Arithmetic Expression
Operator Description Associativity Rank
& Bitwise AND Left to right 8
^ Bitwise XOR Right to Left 9
| Bitwise OR Left to right 10
&& Logical AND Left to right 11
|| Logical OR Left to right 12
?: Conditional expression Right to left 13
=,*=,/=,%=,+=,-= Assignment operators Right to left 14
, Comma operator Left to Right 15

72
Operator Precedence in C is used to determine the sequence in
which different operators will be evaluated if two or more
operators are present in an expression.
The associativity of operators: is used to determine whether an
expression will be evaluated from left-to-right or from right-to-
left if there are two or more operators of the same precedence.
E.G c=a*5/5 ------------Here
 a-b/3+c*2-1
a=9, b=12, c=3
 a-b/(3+c)*2-1
1. Parentheses have the highest precedence among all
operators in C.
Operator Precedence

73
printf("%d", 1 == 3 != 5);
Operator Precedence
Z=++a * (3 + 8) % 35 - 28 / 7;
z = a++ + ++a;
a > b > c

74
Macros in C
The macro in C language is known as the piece of code which can
be replaced by the macro value.
The macro is defined with the help of #define preprocessor
directive and the Macro doesn’t end with a semicolon(;).
Whenever the compiler encounters the macro, it replaces the macro
name with the macro value.
e.g #define PI 3.14
#: preprocessor directive
PI macro name
3.14 Macro Value
Q: Write a program to calculate the area of a circle with a macro
definition for PI( Given that diameter of the circle is 16 cm)
#define MARKS 100
#define MIN 1
#define G 9.8

75
Sr. No. Macro Feature
1 __LINE__ Macro
It contains the current line
number on which this macro is
used.
2 __FILE__ Macro
It contains the name of the file
where the current program is
present.
3 __DATE__ Macro
It contains the current date in
MMM DD YYYY format.
4 __TIME__ Macro
It contains the current time in
HH:MM format.
5 __STDC__ Macro
It is defined as 1 when there is a
successful compilation.
Predefined Macros and their features:

76
IF Statement:
The if statement is a simple decision-making and branching
statement and it is used to control the flow of the program
execution.
IF Statement
It means depending on the condition the control is transferred either to the
true block or false block. It is also called a control statement.
Condition
check
True
False

77
if(expression)
#include<stdio.h>
int main()
{
int a=10;
float b=50;
if(a>b)
{
printf("yes %d",a);
}
return 0;
}
#include<stdio.h>
int main()
{
char a=‘1’;
float b=50;
if(a>b)
{
printf("yes %d",a);
}
return 0;
}

78
int main()
{
int a=10;
int b=50;
int c=500;
if(a>b>c)
{
printf("yes %d",a);
}
return 0;
}
#include<stdio.h>
int main()
{
int a=10;
int b=5;
int c=0;
if(a>b>c)
{
printf("yes %d",a);
}
printf("outside if statement");
return 0;

79
Types of If Statements
if statement may be implemented in different
forms depending on the complexity of testing
conditions to be evaluated.
•Simple if Statement
•if-else Statement
•Nested if-else Statement
•else-if Ladder
Condition
check
True
False
If Block
Else
block

80
Program to check whether a person is eligible to vote or not. Given that age must be
equal to or greater than 18
Q. Write a program that takes integer input from the user. Based on that input you have to
decide whether the integer input is an even or odd number
Find out the given number is even or not using Ternary Operator in C.
(num % 2 == 0)

81
If Else Ladder
if(condition) { }
else if(condition) {
// this else if will be executed when condition in if is false and //
the condition of this else if is true }....
// once if-else ladder can have multiple else if else { // at the end
we put else }
if()
{
}
Else if()
{
}
Else if()
{
}
else
Write a program to Check whether a number is positive,
negative or 0
Calculate Grade According to marks using if else ladder.
Given that:
marks less than 100 and marks greater or equal 90 --A
marks less than 90 and marks greater or equal 70 --B
marks less than 70 and marks greater or equal 50 --C
marks less than 50 and marks greater or equal 40 --D
marks less than 40 and marks greater or equal 0 --F
other than this marks are not valid

82
if (condition 1) {
//if the second condition holds
if (condition 2)
{ do something }
//if the second condition does not hold
else { do something else }
}
// if the first condition does not hold
else{ //if the third condition holds
if (condition 3)
{ do something }
//if the third condition does not hold
else
{ do something else }
}
Nested If Else Statement
Write a program to find Which number is greatest among the three numbers that
the user has received as input

83
Write a program to analyze if the number is even or odd, and then if it is even, whether it is divisible by 4
or not, and if it is odd, whether it is divisible by 3 or not
Write to program to Check if a year is a leap year
Write a program to find Which number is greatest among the three numbers that the
user has received as input
4
100
400
Write a program to multiple variable with a constant without using multiplication
operator.

84
Every year that is evenly divisible by four is a leap year except for years
that are evenly divisible by 100 and 20For example, 2014, 2015, 2017,
and 2018 are not leap years because they are not evenly divisible by
four, 2012, 2016, 2020, and 2024 are leap years because they are evenly
divisible by four and not evenly divisible by 100, 1800, 1900, 2100, and
2200 are not leap years because they are evenly divisible by 100 and not
evenly divisible by 400, and 1600, 2000, and 2400 are leap years
because they are evenly divisible by 400. All these rules makes the
average calendar year 365.2425 days, which is fairly close to the actual
time it takes for Earth to orbit the sun, which is slightly less than 365.2422
days

85
The math.h header defines various mathematical functions and one macro. All the functions
available in this library take double as an argument and return double as the result.
double ceil(double x): The C library function double ceil (double x) returns the smallest integer
value greater than or equal to x.
double floor(double x): The C library function double floor(double x) returns the largest integer
value less than or equal to x.
double fabs(double x): The C library function double fabs(double x) returns the absolute value of x
double fmod(double x, double y) : The C library function double fmod(double x, double y)
returns the remainder of x divided by y.
sqrt(double x): The C library function double sqrt(double x) returns the square root of x
double pow(double x, double y): The C library function double pow(double x, double y) returns
x raised to the power of y i.e. xy.

86
The term b2; - 4ac is known as
the discriminant of a quadratic
equation. It tells the nature of the roots.
If the discriminant is greater than 0, the
roots are real and different.
If the discriminant is equal to 0, the
roots are real and equal.
•If the discriminant is less than 0, the
roots are complex and different.
Write a program to find roots of a quadratic equations

88
#include<stdio.h>
int main()
{
int i,j;
i=10;
j=10;
if(i==1)
{
printf("how are you");
}
else if(i==10)
{
printf("yes");
}
else if(i==10)
{
printf("no");
}
return 0;
}
#include<stdio.h>
int main()
{
int i,j;
i=10;
j=10;
if(i==1)
{
}
else if(i==10)
{
printf("yes");
}
else if(j==10)
{
printf("no");
}
return 0;
}

89
C program to count the total number of notes in a given amount
Int a=5;
Printf(%d %d %d %d %d”, a,--a,--a,--a,--a);
Printf(%d %d %d %d %d”, a, a++,a++,a++,a++);
C program to swap two numbers using temporary variable?
C program to swap two numbers without using a temporary
variable?

90
Formatted output
Printf(“%d”,9876)
Printf(“%6d”,9876)
Printf(“%2d”,9876)
Printf(“%-6d”,9876)
Printf(“%06d”,9876)
9 8 7 6
9 8 7 6
9 8 7 6
9 8 7 6
0 0 9 8 7 6

91
Formatted output
Printf(“%7.4f”,98.7654)
Printf(“%7.2f”, 98.7654)
Printf(“%-7.2f”, 98.7654)
Printf(“%f”, 98.7654)
9 8 . 7 6 5 4
9 8 . 7 7
9 8 . 7 6 5 4
9 8 . 7 7

92
int main()
{
printf(" %d", printf("%s", “how are you"));
getchar();
}
int main()
{
int a ;
int z= scanf("%d ", &a);
printf(" %d",z );
getchar();
}
X=Printf(“hello”);
Printf(“%d”, x);

93
Getchar(): Reading a single character can be done using the function getchar
Variable_name=getchar();
C Supports many other similar functions which are contained in the filetype
ctype.h
#include<ctype.h>
 Isalnum(c)
 Isalpha(c)
 Isdigit(c)
 Islower(c)
 Ispunct(c)
 Isspace(c)
 Isupper(c)

94
Like getchar, there is an analogous function putchar for writing charactrs one at a time
to the terminal
Putchar(variable_name)
e.g
putchar(toupper(alphabet));
Write a program that reads a character from the keyboard and then prints the reverse case. That
is if the input is lower case output will be upper case and vice versa without using predefined
functions
Write a program that reads a character from the keyboard and then prints the reverse case. That
is if the input is lower case output will be upper case and vice versa using predefined functions

96
int main()
{
char a;
a= getch();
printf("%c", a);
return 0;
}
getch():
getch() is a nonstandard function and is present in conio.h header file which is mostly used by MS-DOS compilers
like Turbo C.
It reads also a single character from the keyboard. But it does not use any buffer, so the entered character is
immediately returned without waiting for the enter key.

97
int main()
{
char a;
a= getc(stdin);
printf("%c", a);
return 0;
}
getc():
It reads a single character from a given input stream and returns the corresponding integer value (typically
ASCII value of read character) on success. It returns EOF on failure.

98
getchar():
The difference between getc() and getchar() is getc() can read from any input stream,
but getchar() reads from standard input. So getchar() is equivalent to getc(stdin)..
int main()
{
printf("%c", getchar());
return 0;
}

99
int main()
{
char a[10];
gets(a);
puts(a);
}

100
Switch in C
The switch statement in C is an alternate to if-else-if ladder statement which allows us to execute multiple
operations for the different possibles values of a single variable called switch variable.
Switch(Expression)
{
case value1:
block1
break;
case value2:
block2
break
Default:
default block
break;
}
In a switch statement, the “case
value” can be of “char” and “int”
type

101
The expression provided in the switch should result in a constant value otherwise it would not
be valid.
For example:
Valid expressions for switch –
switch(1+2+23)
switch(1*2+3%4)
Invalid switch expressions –
switch(ab+cd)
switch(a+b+c)
The default statement is optional, if you don’t have a default in the program, it would run just
fine without any issues. However it is a good practice to have a default statement so that the
default executes if no case is matched.

102
#include <stdio.h>
int main() {
int number=1;
switch (number) {
case 1:
case 2:
case 3:
printf("One, Two, or Three.n");
break;
case 4:
case 5:
case 6:
printf("Four, Five, or Six.n");
break;
default:
printf("Greater than Six.n");}}

Create a grading system using a switch case
100-90->A
80 -90->B
60-80->C
40-60->D
30-40->E
<30->F
103

106
We consider the following program in which the user to type his class group
Number(15,17,19), if the Group ID (15,17,19)is valid it will ask him to enter his Roll NO(1-
5), if the Roll No is correct the program will print message “ Welcome to CSE” to the user,
otherwise ,the program will print Incorrect Roll NO and if the Group ID does not exist , the
program will print Incorrect Group ID.
Please Enter Your Group ID: 17
Enter your RollNO: 15
Incorrect Roll NO
Enter your RollNO: 5 Welcome to
CSE
Incorrect Group ID

107
Write a program to convert the given two-digit number into English word format with the help
of a switch case.
e.g 7-> seven
Using the switch case, write a program in which the user selects any operator among +,-,*,/ then
the program asks for two integers, and after that performs the required operation on given two
integers.

108
Necessary Use switch case and/or if else if required, Write a program that asks for two inputs
year and month number(1-12). Based on the year and month number, calculate the total number
of days from the Month Jan
E.G year:2020
month: 3
total days= 91

109
Necessary Use switch case and/or if else if required, Write a program that asks for two inputs
year and month number(1-12). Based on the year and month number, calculate the total number
of days from the Month Jan
E.G year:2020
month: 3
total days= 91

110
A computer manufacturing company has the following monthly compensation policy to
their sales persons:
Minimum base salary: 1500
Bonus for every computer sold :200
Commission on the total monthly sales :2 percent (0.02)
The sales price of each computer is fixed at the beginning of every month.
Write a program to compute a sales persons gross salary
Hint gross salary=Base salary+bonus+comissions
Test Case
Input number sold and price
5 20430.00
Bonus= 1000.00
Comission=2045
Gross salary =4545.00

111
A electric power distribution company charges its domestic consumers as follows
Consumption Units Rate of charge
0-200 Rs 0.50 per unit
201-400 Rs 100 plus Rs 0.65 per unit excess of 200
401-600 Rs 230 plus Rs 0.80 per unit excess of 400
601 and above Rs 390 plus 1.00 per unit excess of 600
Write a program that reads customer number, power consumed, and print amount paid
by customer.
Test Case:
input
Customer N0 :101
Units consumer : 202
Output :
Charges 116

113
C supports the goto statement to branch unconditionally from one point to another in the
program.
The goto statement requires a label in order to identify the places where the branch is to be
made.
The label is any valid variable name and must follow a colon:
Goto label;
Label:
Statement;
Label:
Statement;
Goto label;
Forward jump
Backward jump

114
#include<stdio.h>
int main()
{
int i=0;
count:
i=i+1;
printf("%dt",i);
if(i<100)
goto count;
return 0;
}

115
Loop
In looping, a sequence of statements is executed until some conditions for terminations of the
body of the loop and others known as control statements.
Control Statements: tests certain conditions and directs the repeated execution of the
statements contained in the body of the loop.
Test
conditions
Body of loop
Entry controlled loop
Test
condition
s
Body of loop
Exit controlled loop
entry entry
False
true
False
true
Pre-test Post test

116
Based on the nature of the control variable and the kind of value assigned to it for testing the
control expression, the loops may be classified into two general categories:
1. Counter-controlled loops: when we know in advance exactly how many times the loop will be
executed
2. Sentinel-controlled loops: a special value called sentinel value is used to change the loop
control expression from true or false

117
While(test condition)
{
Body of the loop
}
While loop is an entry controlled loop statement
Sum=0;
n=1;
while(n<=10)
{
Sum=sum+n*n;
n=n+1;
}
Printf(“sum=%d”, sum);
Character =‘’
While(character!= ‘y’)
Character=getchar();
//sentinel control loop
While Loop

118
The do-while loop is a post tested loop
do{
1.//code to be executed
2.}
3.while(condition);
1 2 3 4 5 5 7 8 9 10
----------------------
1
2
3
4
5
6
7
8
9
10
Do While Loop

119
Write a program to find the factorial of number using while loop
Write a program to reverse a given number e.g 123 -> 321
Write a program using while loop and print the following:
1 1
2 2
3 3
4 4
5 5
6 6

120
Write a program using a while loop and print the following pattern:
1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
3 6 9 12 15 18 21 24 27 30
4 8 12 16 20 24 28 32 36 40
5 10 15 20 25 30 35 40 45 50

121
Write an interactive program to demonstrate the process of multiplication. The program
should ask the user to enter two-digit integers and print the product of integers as
shown below
37x45 is ------------------------------ 45
x 37
---------
315
135
-------------
add them 1665
--------------

Jump in loops 122
Break: When a break statement is encountered inside a loop, the loop is immediately
exited and the program continues with the statement immediately following the loop
Goto: An important use of goto is to exit from deeply next loops when an error occurs. A
simple break statement would not work here.

Skipping a part in loops 125
Continue: The continue statement causes the loop to be continued with the next
iteration after skipping any statements in between
SKIP THE FOLLOWING STATEMENTS AND CONTINUE WITH NEXT ITERATIONS
continue;

126
#include<stdio.h>
int i=1;
int main()
{
while(i<10)
{
if(i==5)
{
printf("This is %dn",i);
continue;
printf("cant print it");
}
printf("hello %dn",i);
i++;
}
}
for(i=0;i<10;i++)
{
printf("the value of i is %d",i);
if(i==7)
{
printf("the value now is %d",i);
continue;
}
printf(" this should be printedn");
}
}

127
For(initialization; test-condition;increment/decrement)
{
Body of loop
}
FOR Loop
 Initialization of the control variables is done first, using an assignment statement such as i=1.
 The value of the control variable is tested using the test condition. The test condition is a
relational expression such as i<2 that determines whether the n loop terminates
 When the body of the loop is executed, the control is transferred back to for statement after
evaluating the last statement in the loop.
 Now control variable is incremented using an assignment statement such as i=i+1

128
for(x=0;x<=10;x=x+1)
{
Printf(“%d”,x)
}
FOR Loop
Additional features of For loop
 More than one variable can be initialized at a time in the for loop
for(n=0,p=1;n<10;n++)
 The test condition may have a compound relation and increment section may also have more
than one part
Sum=0;
For(i=1,j=1; i<20 &&sum<100; ++i,++j)
{
sum=sum+I;
j=j+I;
printf(“%d %d ”,j,sum);
}

129
FOR Loop
Additional features of For loop

m=5;
for( ; m!=50 ;)
we can omit one or more sections of for loop if necessary

130
{
{
}
}
for(i=1; i<=5;++i)
{
for(j=1; j<=5;++j)
{
}
}
Nested FOR Loop

131
{
{
{
}
}
}
for(i=1; i<=5;++i)
{
for(j=1; j<=5;++j)
{
for(z=1; z<=5;++z)
{
}
}
}
Nested FOR Loop

132
For Columns loop2
For
Rows
Loop1
For Pattern printing loop3

133
12345678910 11111
22222
33333
44444
55555
1
2
3
4
5
6
7
8
9
10
*****
*****
*****
*****
12345
12345
12345
12345
12345
987654321
*
* * *
* * * * *
* * * * * * *
1
12
123
1234
12345
12345
1234
123
12
1
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1
1 1
1 1 1
1 1 1 1
1 1 1 1 1
* * * * * * *
* * * * *
* * *
*
1 2 3 4 5 6 7
1 2 3 4 5
1 2 3
1
- - - -1
- - - 2 3
- - 3 4 5
- 4 5 6 7
5 6 7 8 9
LEVEL 1
LEVEL 2
LEVEL 3
S S S S S
S S
S S
S S
S S S S S

134
Write a function in c that Converts Binary Numbers to Decimal
Write a program to find Prime Numbers Between Two Integers
 Pre-condition check:
 if number 1> number 2 swap the two numbers.

135
Write a program to check whether a number is a prime number or not
*without using function*
Write a program to find Prime Numbers Between Two Integers
 Pre-condition check:
 if number 1> number 2 swap the two numbers.
Write a program to find whether a number is an Armstrong number or not
Write a program to print Fibonacci Series
 User specifies the total number of elements to
be printed
The Fibonacci numbers are the numbers in the following integer
sequence.
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144,

ARMSTRONG NUMBER
136
1634, 8208, 9474
Write a program to find whether a number is an Armstrong number or not

137
C Program to draw pascal triangle
LAB WORK

138
FIND ODD NUMBER BETWEEN 1 AND 100
FIND THE SUM OF N NATURAL NUMBERS
FIND THE SUM OF THE FIRST N ODD NUMBERS
FIND THE SUM OF FIRST N EVEN NUMBERS
LAB WORK
C Program to convert decimal numbers to binary
C Program to Convert Binary Numbers to Decimal

140
User Defined Functions
C functions can be classified into two categories, namely:
 Library functions
 User-defined functions
*main is an example of user-defined functions.
If a program is divided into functional parts, independently codes a program called subprograms, in C such
subprograms are called functions.
Function: A function is a self-contained block of code that performs a particular task.
Once a function has been designed it is treated as a black box that takes some data from the main
program and returns a value.
The inner details of operations are invisible to the rest of the program

141
Elements of User DefinedFunctions
 Like variables functions have types (such as int) associated with them
 Like variables, function names and their types must be declared and defined before they are used in the
program.
We need to established three elements that are related to functions
 Function definition
 Function call
 Function declaration
Void printl(void); /*declaration */
Main()
{
printl();
}
Void printl(void)
{
statements……….
------------------------
}

142
Functions definitions
Function definition: A function definition, also known as function implementation shall include the
following elements.
 Function name;
 Function type;
 List of parameters
 Local variables declarations
 Function statements
 Return statement.
Function_type function_name(parameter list)
{
Local variables declaration;
Executable statement;
-------------------
------------------
Return statement;
}

143
Function type
Function type specifies the type of value(like float and double) that the function is expected to return to
the program calling the function.
 if the return type is not explicitly specified , C will assume that it is a integer type.
 if function is not returing anything then we need to specify the return type as
void
Void is one of the fundamental data type in C.

144
Formal parameters List
The parameter list declares the variables that will receive the data sent by the calling program.
They serve as input data to the function to carry out the specified task.
Since they represent actual input values they are called as formal parameters.
The parameters list contains the declaration of variables separated by commas and surrounded by
parentheses.
Float quadratic(int a, int b, int c)
double power(double x, int n)
float mul(float x,floaty)
int sum(int a, int b)
Int sum(int a,b)
Is illegal

145
void
If function has no formal parameters, to indicate the parameter list is empty, we use keyword void
between the parentheses as in
Void printl(void)
{
}
Many compilers accept an empty set of parentheses, without specifying anything as in
void printl()
But is a good programming style to use void to indicate a nill parameter list

146
Function Body
The function body contains:
 Local declaration that specifies the variables
 Function statements
 A return-type statement
*if the function can’t return we can omit the return statement. However, its return type should be
specified as void.
When a function reaches its return statement, the control is transferred back to the calling
program,-----------in Absence of a return statement, the closing brace acts as a void return;
A local variable is a variable that is defined inside a function and used without having any role in the
communication between functions.
Float mul(float x, float y)
{
Float result; /*local variable*/
Result=x*y;
Result(result);
}

147
Return Values and their types
The return type can take one of the following forms:
1) Return; -----------Doesn’t return any value and acts much as closing brace of the function
in C99, if a function is specified as returning a value, the return value must have value associated
with it
Or
2)Return (expression)
The function can return only one value per call
Int product (void)
{
Return (2.33* 5.1)
}
will return the value of 7 (automatically casted to function type)

148
Function calls
A function can be called by simply using the function name followed by list of actual prameters
(or arguments)
Int main()
{
Int y;
Y=mul(5,3);
}
Int mul(int x, int y)
{
Int z;
Z=x*y;
Return (z);
}
Printf(“%d”, mul(p,q));
A function that return values can
be used in expressions like:
If(mul(p,q)>total)

149
Function declaration
All functions in a c program must be declared before they are involved.
A prototype declaration may be placed in two places in a program
 Above all the functions including the main(global prototype)
 Inside a function definition. (local prototype)
The place of declaration of a function defines a region in a program in which the function may
be used by other functions. This region is known as the scope of the functions.

char pri(void);
int main()
{
char x;
x= pri();
printf("%c",x);
}
char pri(void)
{
return 'a';
}
150
int main()
{
char x;
pri();
printf("Fine");
}
void pri(void)
{
}

#include<stdio.h>
void swap(int,int);
void main( )
{
int n1,n2;
printf("Enter the two numbersn");
scanf("%d%d",&n1,&n2);
printf("nThe values of n1 and n2 before calling the swap function
are n1=%d n2=%d",n1,n2);
swap(n1,n2);
printf("nThe values of n1 and n2 after calling the swap function
are n1=%d n2=%d",n1,n2);}
151

152
void swap(int n1,int n2)
{
int temp;
temp=n1;
n1=n2;
n2=temp;
printf("nThe values of n1 and n2 after swapping are n1=%d
n2=%d",n1,n2);
}

153
#include<stdio.h>
void prn(int,int);
;
int main()
{
int a,b
int x=10,y=12;
printf("a= %d and b= %d",x,y);
prn(x,y);
}
void prn(int x , int y)
{
a=x+1;
b=y+1;
printf("value of a=%d and value of b=",a,b);
}

154
Write a user-defined function to calculate the Volume of the cylinder where another user-
defined function returns the square of the net radius.
Given that the outer radius is the cylinder is 16cm and the inner radius is 8cm and the height of the
cylinder is 25cm
Write a user-defined function that returns the age in years of a person.
Enter Date of birth details
Day:
month:
Year:
Enter current day:
Enter current month:
Enter current year:

156
Storage classes
In some programming languages, variable retains its value throughout the program like BASIC
PROGRAM.
But that is not the case with C programming
It depends on the storage class a variable may assume.
In C , variable not only have data types but the storage classes.
Following are the storage classes , relevant to functions
1. Automatic variables
2. Register variables
3. Static variables
4. External variables

157
Storage classes
Variable have scope, visibility and longevity
Scope: determines over what region of the program a variable is actually available
The scope of a variable is determined at compile-time only
In Simple words, if you use a variable out of its scope compiler will throw an error
Longevity: refers to the period during which a variable retains a given value during execution of a
program
Visibility refers to the accessibility of a variable from the memory
Default definition value:
Memory allocation does not happen in the declaration whereas in definition memory gets
allocated to the variable.

158
Variable declaration is useful when the programmer uses multiple files and when he defines
the variables in one of the files. They are available when linking the program. He can use the
variable in any place. Even though it is possible to declare a variable multiple times in
it only once such as in a file or a function.
What is a Definition in C
The definition of a variable indicates the compiler where and how much storage to create for
the variable. A variable definition defines the data type and a set of one or more variables of
that type. Below is an example of a declaration.
int a, b;

159
Automatic Variables
Automatic Variables: are declared inside a function in which they are utilized,
They are created and destroyed automatically when the function is exited.
They are also called local or internal variables
A variable declared inside a function without storage class specification is by default an automatic
variable
Main()
{
Int number
}
_____________________________________________________________
Main()
{
Auto number
}
#include<stdio.h>
auto int max; //Error, illegal to declare auto with global scope.
int main()
{
auto int min; // Legal syntax
}

10
100
1000
160
Void fun1(void);
Void fun2(void);
Main()
{
Int m=1000;
Fun2();
printf(%d ,m);
}
Void fn1(void)
{
Int m=10;
Printf(“%d”,m);
}
Void fun2(void)
{
Int m=100;
Fun1();
Printf(“%d”, m);
}

161
Register Variables
Register Variables: tells the compiler that the variable should be kept in one of the machine’s registers,
instead of kept in the memory(where normal variables are stored). Since register access is faster than
memory access, keeping the frequently accessed variables (e.g loop variables in the register will lead to
faster execution of programs.
Register int count;
Some compilers allow only int and char variables but ANSI standard doesn’t restrict its
application
C will automatically convert register variables into non-Register variables once the limit is reached

162
Static Variables
Static Variables: the value of static variables persists until the end of the program.
A static variable is declared using static keyword
Static int x;
Static float y;
Internal Static variables are similar to auto variables except they remain in existence (alive)
through out the remainder of the program.
internal static variable can be used to retain values between function calls.

163
#include<stdio.h>
static int out;
// Global static variable implicitly initialized to 0.
void main()
{
static int in = 10;//local static variable explicitly initialized to 10
printf("global: %d, local: %d", out, in);
}
two static variables with the same definition in two different functions refer to two
different memory locations and hence they are not be assumed as a single variable.
For example in the below code,
void fun1()
{ static sInt = 100; }
void fun2()
{ static sInt = 10; }

164
Void stat(void);
Int main()
{
Int I;
For(i=1;i<=3;i++)
{
stat();
}
}
Void stat(void)
{
Int x=0;
x=x+1;
Printf(“%dn, x);
}
Void stat(void);
Int main()
{
Int I;
For(i=1;i<=3;i++)
{
stat();
}
}
Void stat(void)
{
Static Int x=0;
x=x+1;
Printf(“%dn, x);
}

165
#include<stdio.h>
void stat(void);
int main()
{
int i;
for(i=1;i<=3;i++)
{
stat();
}
printf("%d",x);
}
void stat(void)
{
int x=0;
x=x+1;
printf("%dn", x);
}
#include<stdio.h>
void stat(void);
int main()
{
int i;
for(i=1;i<=3;i++)
{
stat();
}
printf("%d",x);
}
void stat(void)
{
static int x=0;
x=x+1;
printf("%dn", x);
}

166
External Variables
External variables: variables that are both alive and active throughout the entire program are known as
external variables. They are also known as global variables.
In case a local variable and global variable have the same name, the Local variable has precedence over
the global variable.
Int fun1(void);
Int x; /*global */
Main()
{
X=10;
Printf(“%d”,x);
Printf(“%d,fun1());
}
Fun1(void)
{
x=x+10;
}

167
External Variables
Global variables available only from the point of declaration to the end of the program.
• Main()
• {
• y=5;
• }
• Int y; /*global declaration*/
• func1()
• {
• y=y+1;
• }
Global variables are initialized with
zero by default

168
Extern Variables
Declare the storage class with the extern.
Main()
{
Extern int y;
}
IT informs the compiler that y is an integer type defined somewhere else in the program
extern declaration doesn’t allocate storage space for variable
Extern keyword:
The extern keyword is used to declare a global variable, it is just a reference to the compiler
that the variable definition is somewhere in the program or in another file

169
#include<stdio.h>
void main() {
extern int m;
m=15;
printf("%d",m);
}
int max;
Extern variables are useless when used in the same
file. They are mainly designed to export global
variables from another file.

#include<stdio.h>
int x;
int main()
{
int y;
printf(“%d %d”, x, y);
}
170

171
#include<stdio.h>
Void main()
{
Extern int i=10;
Printf(“%d”,i);
}
#include<stdio.h>
void main()
{
extern i;
i=10;
printf("%d",i);
}
int i=20;
#include<stdio.h>
void main()
{
extern i;
printf("%d",i);
}
int i=20;

172
Storage Class Scope Lifetime Initial Value
Storage
Location
Auto
Within the
block, in which
it is declared.
Within the
block, in which
it is declared.
Initialized with
garbage value.
RAM
Register
Within the
block, in which
it is defined.
Same as auto,
within the
block in which
it is declared.
Initialized with
garbage value.
Register
Static
Within the
block, in which
it is defined.
Throughout
the main
program.
Zero. RAM
Extern
Global scope,
unbound by
any function.
Same as static,
till the end of
the main
program.
Zero. RA

173
Arrays
C Supports derived data type called array that can be used to store, process ,
print and manipulate large amount of data.
Array is a fixed-sized sequenced collection of elements of the same data type.
The array is classified as one of the data structures in the C
A data structure is a specialized format for organizing, processing, retrieving and storing data.

174
Arrays
Declaration of Array : int number[10]; This declaration is also called as vector
The computer reserves five storage locations:
3
4
1
2
8
Number[0]
Number[1]
Number[2]
Number[3]
Number[4] Subscripts of an array begin with 0 and can
be integer constant, inter variables, or
expression that yields to integers
An array is allocated block of memory for the specified no.
of elements in contiguous or continuous locations by the
compiler.

175
Arrays
Any reference to the array outside the declared limits would not necessarily cause an error. Rather
it might result in unpredictable program results.
C language treats character strings simply as an array of characters.
Char name[10];
“Welcome to”
‘W’ ‘E’ ‘L’ ‘C’ ‘O’ ‘M’ ‘E’ ‘ ’ ‘T’ ‘O’ ‘/0’
float marks[5] = {67, 89.5, 45.8, 60, 48.6};
/* marks contains 5 floats */
Let’s see how these 5 floats are organised in marks,
marks[0] = 67;
marks[1] = 89.5;
marks[2] = 45.8;
marks[3] = 60;
marks[4] = 48.6;

176
Initialization Arrays
Array can be initialized at either of following stages:
At compile time
At run time
Compile Time Initialization
Int number[5]={1,2,3,4,5};
Float marks[5]={1.2,3.5,5.5} // the remaining two elements to
zero in case of number and null in case of character array
The size may be omitted, in such cases, the compiler allocates enough space for all
initialized elements.
int number[ ]={1,2,3,};

177
Char name[ ]={‘c’,’h’,’I’,’t’,’k’,’r’,’a’};
An alternative way is char name [ ]=“chitkara”;
Int number [3]={10,20,30,40};
#include<stdio.h>
int main()
{
char number[3]={'j','o','m','p','i'};
printf("%c",number[3]);
}

178
#include<stdio.h>
int main()
{
int number[3]={1,2};
printf("%d",number[2]);
}
#include<stdio.h>
int main()
{
int number[3]={1,2};
printf("%d",number[3]);
}
#include<stdio.h>
int main()
{
char number[3]={'j','o'};
printf("%c",number[2]);
}
#include<stdio.h>
int main()
{
char number[3]={'j','o'};
printf("%s",number[2]);
}

179
Run Time Initialization

Passing array to a function 180
#include <stdio.h>
void display(int r1, int r2)
{
printf("%dn", r1);
printf("%dn", r2); }
int main()
{
int rollno[] = {2, 8, 4, 12}
display(rollno[0], rollno[1]);
return 0;
}

181
float calculateSum(float num[]);
int main()
{
float rollno[] = {2, 5, 6, 3, 4, 8};
result = cadd(rollno);
}
float calculateSum(int abc[])
{
}

WRITE A PROGRAM TO SORT AN N-ELEMENTS ARRAY
182
WRITE A C PROGRAM FOR LINEAR SEARCH IN C
FIND THE LARGEST ELEMENT IN AN ARRAY
FIND THE SUM OF ALL THE ELEMENTS IN AN ARRAY
NOTE : PASS ARRAY TO A FUNCTION WHICH CALCULATES THE SUM OF THE ARRAY
STORE THE ELEMENTS OF ONE ARRAY IN OTHER ARRAY BUT IN REVERSE
ORDER
C PROGRAM TO INSERT AN ELEMENT IN AN ARRAY

183
String in C
The string can be defined as the one-dimensional array of characters terminated by a
null ('0’).
There are two ways to declare a string in c language.
1.By char array
char ch[8]={‘C', ’h', ’i’, ’t', ’k', ’a', ’r', ’a', '0'};
By string literal
Char ch[]=“chitkara”;
We need to add the null character '0' at the end of the array by ourself whereas, it is appended
internally by the compiler in the case of the character array.

184
String functions (strlen)
strlen() function:The strlen() function returns the length of the given string
#include<stdio.h>
#include <string.h>
int main(){
char ch[20]={'c', 'h', 'i', 't', 'k', 'a', 'r', 'a','0', 'n'};
printf("Length of string is: %d",strlen(ch));
return 0;
}

185
String functions (strcpy) and
strncpy
The strcpy(destination, source) function copies the source string in destination.
1.#include<stdio.h>
2.#include <string.h>
3.int main(){
4. char name[4]={‘c’,’a’,’n’,’t’};
5. char name2[4];
6. strcpy(name2,name);
7. printf("Value of second string is: %s",name2);
8. return 0;
9.}
strncpy
strncpy(s1, s2, n) copies the first ‘n’ characters of the second string s2 to the first string s1

186
String functions (strcat)
The strcat(first_string, second_string) function concatenates two strings and result is returned
to first_string
#include<stdio.h>
#include <string.h>
int main(){
char ch[6]={'h', 'e', 'l', 'l', 'o'};
char ch2[3]={'c','i'};
strcat(ch,ch2);
printf("Value of first string is: %s",ch);
return 0;
}

187
String functions (strncat)
strncpy
strncpy(s1, s2, n) copies the first ‘n’ characters of the second string s2 to the first string s1.
char s2[ ]= "Hello";
char s1[10];
strncpy(s1, s2, 2);

188
String functions (strcmp)
strcmp
strcmp(s1, s2) compares two strings and finds out whether they are same or different.
It compares the two strings character by character till there is a mismatch.
If the two strings are identical, it returns a 0.
If not, then it returns -1.
strncmp
strncmp(s1, s2, n) compares the first ‘n’ characters of s1 and s2.
If the two strings are identical, it returns a 0.
If not, it may return the difference between the ASCII values of the first non-matching pair of
characters.

189
#include <stdio.h>
#include <string.h>
int main()
{
char s1[ ]= "Healo";
char s2[ ]= "Hebld";
int i, j;
i = strcmp(s1, "Hello");
j = strncmp(s1,s2,3);
printf("%d n %dn", i, j);
return 0;
}
-1
-1
#include <stdio.h>
#include <string.h>
int main()
{
char s1[ ]= "Heblo";
char s2[ ]= "Heald";
int i, j;
i = strcmp(s1, "Hello");
j = strncmp(s1,s2,3);
printf("%d n %dn", i, j);
return 0;
}
-1
1

190
String functions __
The strrev(string) function returns reverse of the given string.
The strlwr(string) function returns string characters in lowercase. Let's see a simple example
of strlwr() function.
The strupr(string) function returns string characters in uppercase. Let's see a simple example
of strupr() function.

Memory Layout of C program
191

193
C program contains five segments
these are :
text segment.
DS (Data Segment) and
BSS (block started by symbol),
heap segment,
the stack segment

194
Text Segment
 A text segment, also known as a code segment or simply as text, which contains executable
instructions.(compiled program instructions)
 text segment may be placed below the heap or stack(low memory address) in order to
prevent heaps and stack overflows from overwriting it.
 the text segment is sharable so that only a single copy needs to be in memory for frequently
executed programs, the text segment is often read-only, to prevent a program from
accidentally modifying its instructions

195
Data Segment
DS(Initialized data segment):
•It contains the explicitly initialized global and static variables.
•The size of this segment is determined by the size of the values in the program’s source code and does
not change at run time.
•It has read-write permission so the value of the variable of this segment can be changed at run time.
int global_var = 50; //read write permission
const int global_var2 = 30 //read-only permission

196
BSS Segment
BSS _[block staring segment](Uninitialized data segment): //block starting symbol
•It contains all uninitialized global and static variables.
•All variables in this segment initialized by the zero(0) and pointer with the null pointer.
•The program loader allocates memory for the BSS section when it loads the program.

197
Heap Segment
Heap:
•It is used to allocate the memory at run time.
•Heap area managed by the memory management functions like malloc, calloc, free, etc which may
internally use the brk and sbrk system calls to adjust its size.

198
Stack Segment
•It is located at a higher address and grows and shrinks opposite to the heap segment.
•The stack contains local variables from functions and related book-keeping data.
•Each function has one stack frame.
•Stack frames contain the function’s local variables arguments and return value.
•The stack contains a LIFO structure. Function variables are pushed onto the stack when called and
functions variables are popped off the stack when return.
•SP(stack pointer) register tracks the top of the stack.

199
#include<stdio.h>
int main()
{
return 0;
}
Text Segment

200
#include<stdio.h>
int main()
{
return 0;
}
Text Segment

201
#include<stdio.h>
int x=10;
int main()
{
return 0;
}
Data segment

202
#include<stdio.h>
Int y;
int x=10;
int main()
{
return 0;
}
BSS segment

203
Stack
Heap
Bss Segment
Data segment
Text segment
#include<stdio.h>
int a=10;
int b=10;
int c=10;
int main()
{
int vol=volume();
printf("the volume =%d“,vol);
}
int volume()
{
int ar=area(a,b);
int volume= ar*c;
return volume;
}
int area(int x, int y)
{
int area=x*y;
return area;
}
a=10
b=10
C=10
Main()
Int vol
Printf()
return
Volume()
ar, volume
return
area()
X,y,area
return

205
 Pointer is a derived data type
• Pointer contains the memory addresses
• Pointer are used to manipulate the data stored in the memory
Pointers are most efficient in handling arrays
Pointers can be used to return multiple values from a function via function arguments.
Pointers allow c to support dynamic memory allocation
Pointers reduce the length and complexity of programs.
They increase execution speed
Each cell , commonly known as byte has
number called address

206
Int quantity =179;
The system finds a location for the integer variable quantity and puts the value
179 in that location
let us suppose system chose the address 5000 for quantity
179
quantity
5000
v
a
r
i
a
b
l
e
a
d
d
r
e
s
s
v
a
l
u
e
Same like house name with house number
We can access
value with
quantity or
address

207
Since memory address is like number we can assign it to variable and save it in memory.
Such variable that hold memory address are called pointer variables
A pointer variable is a variable that holds the address, which is
the location of another variable in memory
variable value address
quantity 179 5000
p 5000 5078
Since the value of variable p is the address of the variable
quantity we may access the value of quantity by using the
value of p
The variable p points to variable quantity thus p gets the name
pointer

208
Pointer constant: Memory address within a computer are called pointer
constant. We can not change them; we can use them to store data values
Pointer values: we can not save the value of memory address directly. We
can obtain value through variable stored there using address operator &.
The value thus obtained is called pointer value
Pointer Variable: After getting pointer value, it can be stored into another
variable called pointer variable

209
Accessing the Address of a variable
1. The actual location of a variable is machine dependent
p=&quantity
Would assign the address(say 5000) to p
& operator can be used with simple variables or the element of an array.
Illegal use of & operator:
1. &125
2. Int x[30]
&x;
3. &(x+y)
Program………

210
Declaring a pointer variable
1. Every variable must be declared for its type.
1. Pointer variable contains the address that belong to separate data type they must be
declared as pointer.

211
Datatype *pointer_name;
Int *p;
declares the variable p as a pointer variable that points to an integer data type
Important: int refers to the data type of the variable being pointed to by p
Float *x;
X as a pointer to floating point variable;
The declaration cause the compiler to allocate memory locations for the pointer variables p and x.
since the memory location have not been assigned any values, these location may contain some
unknown values

212
Int *p p
? Unknown location
Int* p;
Int *p;
Int * p;

213
Initialization of pointer variable
1. The process of assigning the address of a variable to a pointer variable is called
initialization.
Int *p;
p=&quantity;
Or
Int *p=&quantity;

214
Float a,b;
Int x, *p;
p=&a //wrong
We declare pointer as int type, the system assumes that any address that the pointer will hold
will point to an integer variable.
Compiler doesn’t detect such errors. So be careful to avoid wrong pointer assignment
We can also define
pointer variable with NULL
or 0.
Int *p=NULL
Or
Int *p=0;

215
Accessing a variable through its pointer
1. How to access the value of the variable using pointer?
This can be done using unary operator *(asterisk)
Int quantity, *p, n;
Quantity=10;
p=&quantity;
n=*p
n=*&quantity

216
Symbol Name Description
& Address of operator
Used to find the
address of a variable
∗ Indirection operator
Used to access the
value at an address

217
#include<stdio.h>
int main()
{
int x,*p1, **p2;
x=100;
p1=&x;
p2=&p1;
printf("%dn",p1);
printf("%d",*p2);
printf("%d",**p2);
}

218
Chain of pointers
It is possible to make a pointer to point to another pointer, thus creating a chain of pointers.
Address
2
Address
1
value
p2 variable
p1
This is knows a multiple indirections
Int **p2
This declaration tells the compiler that p2 is a pointer
to a pointer of int type. P2 is pointer to a integer but
pointer to an integer pointer

219
Pointer Expression
Like other variables , pointe variables can be used in
expression, e.g if p1 and p2 are properly initialized
then
Y=*p1 * p2;
Z=*p2/ *p1;
C allows us to add and subtract integers from pointers.
 P1+4;
 P2-2;
 P1-p2 are allowed if both pointer are of same array.
-then p1-p2 gives the number of elements b/w p1
and p2;
P1>p2 or p1==p2, are allowed , if they don’t refer to separate and
un realted variables.
P1/p2 or p1*p2 or p1/5 are
not allowed

a=2
b7=
Z=8
220
Write a program to illustrate the use of pointer in arithmetic operations
int main()
{
int a, b, *p1, *p2, x,y,z;
a=12;
b=4;
p1=&a;
p2=&b;
x=*p1 * *p2 -6;
y= 4* -*p2/ *p1 +10;
*p2=*p2+3;
*p1=*p2 -5;
z=*p1 * *p2 -6;
printf( "a= %d ,b =%dn",a,b);
printf("z=%d",z);
}

221
Pointer increment and Scale factor
P2=P2+2;
P1=p1+1;
It will cause the pointer say p1 to next value of its type,
e.g if p1 has value 62280 the after increment by 1 new value will be
62284;
Its value is increase by length of data type called the scale factor

222
#include<stdio.h>
int main()
{
int a, b, *p1, *p2, x,y,z;
a=12;
b=4;
p1=&a;
p2=&b;
x=*p1 * *p2 -6;
y= 4* -*p2/ *p1 +10;
*p2=*p2+3;
*p1=*p2 -5;
z=*p1 * *p2 -6;
printf( "a= %d ,b =%dn",a,b);
printf("z=%d",z);
printf("-------------------------n");
printf("%dn",p1);
p1=p1+1;
printf("%dn",p1);
}

223
Pointers and Arrays
When array is declared, the compiler allocates a base address and sufficient amount of
storage to contain all the elements of the array in contiguous memory locations.
The base address is the location of first element
1 2 3 4 5 6 7
1000 1004 1008 1012 1016 1020 1024
Address of x[4]=Base address + (4 X scale of data type)
1000+4X4= 1016;
Now instead of using index we
can use now pointer to access
the array elements;
P+4;
Which is faster than using
indexing

#include<stdio.h>
int main()
{
int *p ,sum;
int x[5]={5,9,6,3,7};
int i=0;
p=x;
printf("Elements value address");
while(i<5)
{
printf("x[%d] %d %un",i,*p,p);
sum=sum + *p;
i++,p++;
}
printf("n sum= %dn",sum);
printf("n x[0]= %un",&x[0]);
printf("p= %u",p);
ret
224
Write a program using pointers to compute the sum of all elements stored in an array

225
Pointers and character Strings
String are treated like character arrays and therefore they are declared and initialized as follows :
Char str[5]=“hello” ;
Compiler automatically inserts null character ‘0’ at end of string.
Alternative method C supports :
Char *str=“good”;
IT stores address in the pointer variable str.
H E L L O 0
str

226
Run time Assignment:
Char *string1;
String1=“good”;
To print the content of string String1:
Printf(“%s”,string1)
No need to used indirection operator * here

#include<stdio.h>
int main()
{
char *name;
int length;
name="hello";
char *cptr=name;;
printf("%sn",name);
printf("%dn",name);
printf("%dn",cptr);
while(*cptr != '0')
{
printf("%c is stored at %un",*cptr,cptr);
cptr++;
}
length=cptr-name;
printf("n length of string =%d",length);
return 0;
}
227
With the help of pointers, sort an array?
5,7,3,8,9,2
Write a program using pointers to determine the length of characters In string

228
int main()
{int prime[5] = {2,3,5,7,11};
printf("Result using &prime = %dn",&prime);
printf("Result using prime = %dn",prime);
printf("Result using &prime[0] = %dn",&prime[0]);
}
int main()
{
int prime[5] = {2,3,5,7,11};
printf("Result using &prime = %dn",&prime + 1);
printf("Result using prime = %dn",prime + 1);
printf("Result using &prime[0] = %dn",&prime[0] + 1);
}

229
Pointer as function arguments
When we pass the address to a function, the parameters receiving the addresses should be pointer.
The process of calling a function using pointers to pass the address of variable is known as call by
reference.
The function which is called by reference can change the value of the variable used in the
call
Int main()
{
Show(&x);
}
Change(int *p)
{
}

#include<stdio.h>
int main()
{
int x,y;
x=100;
y=200;
printf("before exhange x=%d,y=%dn",x,y);
swap(&x,&y);
printf("After exhange x=%d,y=%dn",x,y);
}
void swap(int *a, int *b)
{
int temp =*a;
*a=*b;
*b=temp;
}
Write a function using pointer to exchange the values stored in two location in memory
230

Function returning pointers
THE FUNCTION CAN RETURN MULTIPLE VALUES THROUGH POINTER PARAMETER. WE
CAN FORCE A FUNCTION TO RETURN A POINTER TO THE CALLING FUNCTION
231
Main()
{
Int a=10;
Int b=20;
Int *p;
P=larger(&a,&b)
Print(“%d”,*p);
Int *larger(int *x , int *y)
{
If(*x>*y)
Return x ; //address of x
}
Else
Return y; //address of y

#include <stdio.h>
void greatestOfAll( int *p){
int max = *p;
for(int i=0; i < 5; i++){
if(*(p+i) > max)
max = *(p+i);
}
printf("The largest element is %dn",max);
}
main(){
int myNumbers[5] = { 34, 65, -456, 0, 3455};
greatestOfAll(myNumbers);
/* Prints :The largest element is 3455" */
}
232
Create a function and Find the largest element in the array by passing address of array to the function(take help of
pointer/s. Also find the size of array both in main function using sizeof operator

234
Write a program in c That passes array as a parameter to function and then adds value
3 to the each element in array using pointers and then updated array is printed in
the main function
Int main()
{
Define array
Call function(array name)
Prints updated array;
}
Function(-------)
{
Adds 3 to each element
}
Given that Elements of array are: 5 6 4 3 2 7
After adding 3: 8,9,7,6,5,10

235
Use sizeof operator find the size of an integer array

236
Pointers to Functions
#include <stdio.h>
int main()
{
printf("Address of main() function is %p",&main);
return 0;
}

237
Pointers to Functions
A function like variable has type and address location in the memory.
it is possible to declare a pointer to a function, which can then be used as a
argument in another function
A pointer to function is decalred as:
Type (*fptr) ();
This tells compiler that fptr is a pointer to a function, which return type value. The
parentheses around around *fptr are necessary .
Statement type *large() would declare large as function returning a pointer to
type

238
int mul(int, int);
Int (*p) ();
P1=mul; //p1 to point mul
We can use the pointer p1 with list of parameters that is
(*p1)(x,y); is same as mul(x,y)

239
1.include <stdio.h>
2.void func1(void (*ptr)());
3.void func2();
4.int main()
5.{
6. func1(func2);
7. return 0;
8.}
9.void func1(void (*ptr)())
10.{
11. printf("Function1 is called");
12. (*ptr)();
13.}
14.void func2()
15.{
16. printf("nFunction2 is called");
17.}
Passing a function's address as an argument to other function

240
#include<stdio.h>
#define PI 3.14
double y(double);
double table(double(*f)(),double, double,double);
int main()
{
printf("Table of y(x)=2*x*x-x+1nn");
table(y,0.0,2.0,0.5);
table(cos,0.0,PI,0.5);
}
double table(double (*f)(), double min, double max,double step)
{
double a,value;
for(a=min; a<=max;a+=step)
{
value=(*f)(a);
printf("%lfn",value);
}
}
double y(double x)
{
return (2*x*x-x+1);
}

241
#include<stdio.h>
int length(int (*fp)(),int l,int b);
int volume();
int main()
{
int l=10;
int b=20;
length(volume,l,b);
}
int length(int (*fp)(),int l,int b)
{
int z=(*fp)();
printf("%d",z*l*b);
}
int volume()
{
return 30;
}

242
#include<stdio.h>
int *add(int*, int*);
int main()
{
int a=10;
int b=12;
int* (*fp)();
fp=add;
int *z=(*fp)(&a,&b);
z=z+20;
printf("%d",z);
}
int *add(int *x, int *y)
{
*x=*x+*y;
printf("%dn",*x);
return x;
}

243
Create a function and swap two arrays with the help of pointers

244
const Pointer in C
A constant pointer in C cannot change the address of the
variable to which it is pointing, i.e., the address will remain
constant. Therefore, we can say that if a constant pointer is
pointing to some variable, then it cannot point to any other
variable.
int *const ptr;
1. int *const ptr;
2. ptr=&a;
3. ptr=&b

245
Pointer to Constant
A pointer to constant is a pointer through which the value of the variable that the
pointer points cannot be changed. The address of these pointers can be changed,
but the value of the variable that the pointer points cannot be changed.
1.const int* ptr;
2. ptr=&b;
3. *ptr=10;

246
Constant Pointer to a Constant
A constant pointer to a constant is a pointer, which is a combination
of the above two pointers. It can neither change the address of the
variable to which it is pointing nor it can change the value placed at
this address.
1. const int* const ptr=&a;
2. *ptr=12;
3. ptr=&b;
4. printf("Value of ptr is :%d",*ptr);

247
void pointer in C
if we declare the int pointer, then this int pointer cannot point to the float variable or some other type of
variable
A pointer to void means a generic pointer that can point to any data type
•Dereferencing a void pointer in C
we print the value of the variable which is pointed by the void pointer 'ptr' by using the
statement given below:
*(int*)ptr;

5 marks question
248
The company was established in 2010 and it was decided that 5 employees were going
to work in the company, So a programmer hired at that time to develop a program for
the company decided to declare an array of size 5 that contains the integer employee id
greater than zero, but, only 3 persons joined the company having employee id 12,13,14
and the vacancy of two employees is still pending. As now you are hired in the same
company as a programmer you are requested to display the current content of the
same array and also the total number of elements(current employees) without
modifying the previous array(size/empid)
Given :
Int empid[5]={12,13,14}
Constraint: As the vacancy of two employees is pending, if they joined their entry is to be done in the same
array and your program must display all the empid’s and count(i.e 5) without changing any line of code.
10 marks question

249
Q1 Write a c program to copy one array to another using pointers
Q2 Write a program to find the reverse of a string using pointers;
Q3 A company needs a program that can manage its inventory of products. Each product has a
name, ID number, price, and quantity in stock. Write a C program that can perform the
following tasks:
1. Add a new product to the inventory by accepting input for the name, ID number, price, and
quantity in stock.
2. Display the current inventory by listing all products and their corresponding information. 3.
Search for a product by ID number and display its information.
4. Exit the program

250
suppose the input list contains the following integer values:
[10, 20, 30, 20, 40, 10, 50, 30]
The program should recognize that the values 10, 20, and 30 are duplicates, and discard all
but one of them, resulting in the following list:
[10, 20, 30, 40, 50]
suppose the input list contains the following integer values:
[10, 20, 30, 20, 40, 10, 50, 30]
The program should recognize that the values 10, 20, and 30 are duplicates, and discard all
of them, resulting in the following list:
[30, 40, 50]

252
2D array will store the data in table form like matrix
consisting of rows and columns
Type Array_name[row size][column size]

253
12 [0][0] 14[0][1] 12[0][2]
34[1][0] 45[1][1] 67[1][2]
23[2][1] 45[2][1] 67[2][1]
Col 0 Col 1 Col 2
Row 0
Row 1
Row 2

254
Initialization of 2D Array in C
int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};
int c[2][3] = {{1, 3, 0}, {-1, 5, 9}};
int c[][3] = {{1, 3, 0}, {-1, 5, 9}};
int c[2][3] = {1, 3, 0, -1, 5, 9};

255
1.Int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};
2.for(i=0;i<4;i++){
3. for(j=0;j<3;j++){
4. printf("arr[%d] [%d] = %d n",i,j,arr[i][j]);
Write a program that do the Sum of two matrices of
size 2x2 and stores the result in third matrix

256
Write a program and Transport the matrix
1 2 3
4 5 6
7 8 9
1 4 7
2 5 8
3 6 9

258
For example:
#include <stdio.h>
int main(void) {
int m,n; int arr[] = {4, 3, 1, 2};
int *p = arr;
}
Now suppose we want a pointer to point to a 2D array. We saw a single pointer can point to
an entire 1D array. So all we need to do is create a pointer for each row/column of the 2D
array.
#include <stdio.h>
int main(void) {
int arr[2][3] = {{3, 2, 1}, {8, 9, 10}};
int *p[2];
p[0] = arr[0]; //Pointer points to first row of 2D array
p[1] = arr[1]; //Pointer points to second row of 2D array
}
Address of 3 Address of 4
3 2 1 4 3 1 2

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