1 Introduction to C Programming.pptx

VELAMMAL ENGINEERING COLLEGE
An Autonomous Institution, Affiliated to Anna University Chennai, &
Approved by AICTE Delhi
Course Title : PROGRAMMING FOR
PROBLEM SOLVING IN
C
Course Code : 19CS101T
1
UNIT I

COURSE OBJECTIVES
• This course aims at giving adequate exposure to students on the
principles of procedural programming language
• The course is intended to introduce the students to computational
thinking and make the students develop C Programs using basic
programming constructs.
• The course will enable the students to apply the fundamentals of C
programming to solve Engineering problems.
UNIT I 2

COURSE OUTCOMES
CO. No. Course Outcome
CO 1 Acquire knowledge on different problem solving techniques.
CO 2 Use appropriate data types and control structures for solving a given problem.
CO 3 Execute different array and string operations.
CO 4 Experiment with the usage of pointers and functions.
CO 5 Organize data using structures and unions.
CO 6 Demonstrate data persistency using files.
UNIT I 3

SYLLABUS
• UNIT-I INTRODUCTION TO PROBLEM SOLVING AND C PROGRAMMING
• Algorithms, building blocks of algorithms (Statements, State,
Control flow, Functions), notation (Pseudo code, Flow Chart,
Programming language), algorithmic problem solving, simple
strategies for developing algorithms (iteration, recursion).
Introduction to C Programming – Data types - Operators and
Expressions – Data Input and Output – Decision making and Looping
Statements.
UNIT I 4

SYLLABUS
• UNIT-II ARRAYS AND STRINGS
• Defining an array – Processing an Single and Two Dimensional array –
Multidimensional Arrays, Character Arithmetic – Defining a string – NULL
character – Initialization of Strings – Reading and Writing Strings – Processing
Strings –Searching and Sorting of Strings.
UNIT I 5

SYLLABUS
• UNIT-III FUNCTIONS AND STORAGE CLASSES
• Defining a function – Accessing a function – Function prototypes – Passing
arguments to a function – Passing arrays to functions – Function with string -
Recursion – Storage classes
UNIT I 6

SYLLABUS
• UNIT-IV POINTERS
• Pointer Fundamentals – Pointer Declaration – Passing Pointers to a Function –
Pointers and one dimensional arrays – operations on pointers– Dynamic memory
allocation.
UNIT I 7

SYLLABUS
• UNIT-V STRUCTURES, UNIONS AND FILES
• Structures and Unions: Defining a Structure – Processing a Structure – User
defined data types (Typedef) – Unions, Files: Opening and Closing a Data File –
Reading and writing a data file – Processing a data file – Unformatted data files –
Concept of binary files – Accessing a file randomly using fseek() & ftell().
UNIT I 8

TEXT BOOKS
• Sumitabha Das, “Computer Fundamentals & C Programming”, Mc
Fraw Hill, 2018.
• Pradip Dey and Manas Ghosh, “Programming in C”, Second Edition,
Oxford University Press, 2011.
UNIT I 9

Introduction
• Computer
• Device capable of performing computations and making logical decisions
• Computers process data under the control of sets of instructions called
computer programs
UNIT I 10

Computer Organization
• Five logical units in every computer:
• Input unit
• Obtains information from input devices (keyboard, mouse)
• Output unit
• Outputs information (to screen, to printer, to control other devices)
• Memory unit
• Rapid access, low capacity, stores input information
• Arithmetic and logic unit (ALU)
• Performs arithmetic calculations and logic decisions
• Control unit
• Supervises and coordinates the various components of the computer

Operation Steps:
• A : The type of operation that the ALU needs to perform is determined by signals from the control unit .
• B: The data can come either from the input unit, or
• C: from the memory unit.
• D: Results of the operation can either be transferred back to the memory unit or
• E: directly to the output unit .
• F : Control signal (a read or a write operation).
• G : A location in memory
• H : Input to memory data lines when the control signal J is enabled.
• I : Memory to the output unit when the control signal L is enabled.
• The instruction word(s) stored at the memory location specified by the address is then transferred to the control unit (K).

Storage Capacities
• bit – smallest capacity (0 or 1)
• nibble = 4 bits
• byte = 2 nibbles = 8 bits
• storage for one character
• 1 kilobyte (KB) = 1024 bytes
• 1 megabyte (MB) = 1024 KB
• 1 gigabyte (GB) = 1024 MB

Programming Language : Definition
• A vocabulary and set of grammatical rules for instructing a computer
to perform specific tasks.
• Programming – the creation of an ordered set of instructions to solve
a problem with a computer.

Evolution of Programming languages
• First Generation : Machine languages
• Strings of numbers giving machine specific instructions
• Example:
+1300042774
+1400593419
+1200274027
• Second Generation : Assembly languages
• English-like abbreviations representing elementary computer operations (translated via assemblers)
• Example:
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY
• Third Generation : High-level languages
• Codes similar to everyday English
• Use mathematical notations (translated via compilers)
• Example: grossPay = basePay + overTimePay

• Programming makes your jobs easy…
UNIT I 17

UNIT-I INTRODUCTION TO PROBLEM
SOLVING AND C PROGRAMMING
Algorithms, building blocks of algorithms (Statements, State, Control flow,
Functions), notation (Pseudo code, Flow Chart, Programming language),
algorithmic problem solving, simple strategies for developing algorithms
(iteration, recursion). Introduction to C Programming – Data types - Operators
and Expressions – Data Input and Output – Decision making and Looping
Statements.
UNIT I 18

What is an Algorithm?
• Computer scientist Niklaus Wirth stated that
Program = Algorithms + Data
• Algorithm-
⮚part of the plan for the computer program
⮚
UNIT I 19

Example of an algorithm-step form :
Making a pot of Tea
1. If the kettle does not contain water, then fill the kettle.
2. Plug the kettle into the power point and switch it on.
3. If the teapot is not empty, then empty the teapot.
4. Place tea leaves in the teapot.
5. If the water in the kettle is not boiling, then go to step 5.
6. Switch off the kettle.
7. Pour water from the kettle into the teapot.
UNIT I 20

BUILDING BLOCK OF ALGORITHMS
Statements- A single action in a computer.
⮚ input data-information given to the program
⮚ process data-perform operation on a given input
⮚ output data-processed result
State
⮚Transition from one process to another process under specified condition within a time
UNIT I 21

Control flow - Executing the individual statements in a given order
1. Sequence(Process)
2. Decision(Selection)
3. Repetition(Iteration or looping)
UNIT I 22

Control flow
1. Sequence (Process)
▪ Each step or process in the algorithm is executed in
the specified order.
▪ All the instructions are executed one after another is
called sequence execution
Example
Add two numbers:
Step 1: Start
Step 2: get a,b
Step 3: calculate c=a+b
Step 4: Display c
Step 5: Stop
UNIT I 23

Control flow
2.Decision(Selection)
▪ A selection statement causes the program control
to be transferred to a specific part of the program
based upon the condition.
▪ Outcome of a decision is either true or false
▪ Outcome is based on some conditions
▪ Decision Constructs: if ... then,
if ... then ... else ...
General form:
if proposition then process
(or)
if proposition
then process1
else process2
UNIT I 24
Example
Algorithm to check whether eligible to
vote?
Step 1: Start
Step 2: Get age
Step 3: if age >= 18
print “Eligible to vote”
Step 4: else
print “Not eligible to vote”
Step 5: Stop

Control flow
3. Repetition(Iteration or looping)
• Iterate or repeat a process or sequence of
processes until some condition becomes
true.
▪ Repetition Constructs: repeat loop
while loop
if.. then .. goto .. loop.
General form1 : Repeat loop
Repeat
Process1
Process2
……………
…………..
ProcessN
Until proposition
UNIT I 25
Example using repeat loop
Repeat
Fill water in kettle
Until kettle is full
Drawback: If the
kettle is already
full at the start of
the Repeat loop,
then filling more
water will lead to
an overflow

General form 2 : while loop
while proposition
begin
Process 1
Process 2
………..
………...
Process N
end
UNIT I 26
Example for repetition using while
loop
while kettle is not full
fill water in kettle
Note :
1. Finds out whether some
condition is true before repeating a
process or a sequence
of processes.
2. If the condition is false, the
process or the sequence of
processes is not executed

General form 3 : if .. then goto ..
Process1
Process2
……….
……….
ProcessN
if proposition then goto Process1
UNIT I 27
Example for repetition using
if .. then goto ..
In the kettle example, this construct
would be implemented as follows:
1. Fill some water in kettle
2. if kettle not full then goto 1
Note : used to repeat a process
or a sequence of processes until the
given proposition is false.

Subroutines
• Method, procedure or function
• Sub program which consists of block of code(set of instructions) that
performs a particular task.
• For complex problems, the problem is been divided into smaller and
simpler tasks during algorithm design.
• Can be called many times with a “CALL” Statement
UNIT I 28

Subroutines-
Advantages:
• Reduction in line of code
• Code reuse
• Better readability
• Information hiding
• Easy to debug and test
• Improved maintainability
Disadvantages:
• Requires computational overhead
UNIT I 29

Questions
• Define an algorithm.
• Building blocks of an algorithm.
• Define subroutine or function.
UNIT I 30

Representation of Algorithm
1. Step-form
2. Pseudo-code
3. Flowchart
UNIT I 32

Representation of Algorithm
• Step-form
⮚ Stated with written statements
⮚ Each statement solves a part of the problem and these together complete the solution
⮚ uses just normal language
• Pseudo-code
⮚ Also written form representation of the algorithm
⮚ Uses a restricted vocabulary (therefore precise)
• Flowchart & Nassi-Schneiderman
⮚ Graphically oriented representation forms.
⮚ Use symbols and language to represent sequence, decision, and repetition actions
UNIT I 33

What are data and variables ?
1.Data is a symbolic representation of value.
numeric data, e.g., 12, 11.45, 901, etc.
alphabetic or character data such as ‘A’, ‘Z’, or ‘This is alphabetic’
logical data, that is, propositions with true/false values
2. A variable, which has a name, is a container for a value that may vary during
the execution of the program.
Variable names are shorter than the original name(Ex:kettle_empty)
UNIT I 34

Ex 1: Write the algorithm for finding the sum of
any two numbers
Solution: Let the two variables be A and B and let their sum be equal to C.
Then, the desired algorithm is given as follows:
1. START
2. PRINT “ENTER TWO NUMBERS”
3. INPUT A, B
4. C A+B
5. PRINT C
6. STOP
UNIT I 35

Ex 2:Construct the algorithm for interchanging the numeric values of two
variables.
Solution :Let the two variables be A and B. Consider C to be a third variable that is used to
store the value of one of the variables during the process of interchanging the values.
1. START
2. PRINT “ENTER THE VALUE OF A & B”
3. INPUT A, B
4. C A
5. A B
6. B C
7. PRINT A, B
8. END
UNIT I 36

Ex 3:Write an algorithm that compares two numbers and prints
either the message identifying the greater number or the message
stating that both numbers are equal.
1. START
2. PRINT “ENTER TWO NUMBERS”
3. INPUT A, B
4. IF A > B THEN
5. PRINT “A IS GREATER THAN B”
6. IF B > A THEN
7. PRINT “B IS GREATER THAN A”
8. IF A = B THEN
9. PRINT “BOTH ARE EQUAL”
10.
UNIT I 37

Ex 4:Write an algorithm for calculating the
factorial of a given number N.
1. START
2. PRINT “ENTER THE NUMBER”
3. INPUT N
4. F 1
5. C 1
6. WHILE C <= N
7. BEGIN
8. F F * C
9. C C + 1
10. END
11. PRINT F
UNIT I 38

FLOWCHARTS
It is a graphical representation of a computer
program in relation to its sequence of
UNIT I 39

FLOWCHARTS
• Program design tool
• Developed in the early stages of formulating computer solutions.
• Set of various standard shaped boxes that are interconnected by flow
lines.
• Flow lines have arrows to indicate the direction of the flow of control
between the boxes.
• Besides flowlines, connector symbols that are used to indicate that the
flow of control continues elsewhere, for example, the next page.
• Better documentation of a complex program
UNIT I 40

FLOWCHART
SYMBOLS
UNIT I 41
Flowchart Symbols

ADVANTAGES
• Communication
• Effective analysis
• Proper documentation
• Efficient coding
• Proper debugging:
• Flowcharts help in the debugging process.
• Efficient program maintenance: UNIT I 42

LIMITATIONS
• Complex logic
• Alterations and modifications
• Reproduction
• Loss of objective
UNIT I 43

FLOWCHART TO FIND SUM OF TWO
NUMBERS
UNIT I 44

FLOWCHART TO FIND SUM OF TWO NUMBERS(SEQUENCE)
START
STOP
COMPUTE
C A+B
PRINT
C
UNIT I 45
INPUT
A,B

FLOWCHART TO FIND MAXIMUM OF TWO
NUMBERS(DECISION)
START
IS
A>B
UNIT I 46
READ A,B
PRINT A PRINT B
STOP
Y N
DECLARE
VARIABLES A,B

FLOWCHART TO FIND SUM OF FIRST N 50 NUMBERS
.
START
STOP
SUM=0
N=0
N=N+1
SUM=SUM+N
IS
N=50?
PRINT
N
Y
N
UNIT I 47

PSEUDOCODE
Pseudocode is an informal way of programming
description that does not require any strict
programming language syntax.
UNIT I 48

Guidelines for writing pseudo code:
❖ Write one statement per line
❖ Capitalize initial keyword
❖ Indent to hierarchy
❖ End multiline structure
❖ Keep statements language independent
UNIT I 49

Common keywords used in pseudocode
1. //: This keyword used to represent a comment.
2. BEGIN,END: Begin is the first statement and end is the last statement.
3. INPUT, GET, READ: The keyword is used to inputting data.
4. COMPUTE, CALCULATE: used for calculation of the result of the given expression.
5. ADD, SUBTRACT, INITIALIZE used for addition, subtraction and initialization.▪
6. OUTPUT, PRINT, DISPLAY: It is used to display the output of the program.
7. IF, ELSE, ENDIF: used to make decision.
8. WHILE, ENDWHILE: used for iterative statements.
9. FOR, ENDFOR: Another iterative incremented/decremented tested automatically.
UNIT I 50

• Problem:
• Addition of two numbers:
EXAMPLE: PSEUDO CODE
UNIT I 51

• Solution:
• BEGIN
• INPUT a,b
• ADD c=a+b
• PRINT c
• END
EXAMPLE: PSEUDO CODE
UNIT I 52

Write a pseudocode for the following:
• Greatest of two numbers
• Factorial of a given number
UNIT I 53

STRATEGY FOR DESIGNING
ALGORITHM
• INVESTIGATION STEP
Determines the requirements for the problem solution
• TOP DEVELOPMENT STEP
• plans out the way the solution has to be done by breaking it into smaller
modules and establishing a logical connection among them.
• STEPWISE REFINEMENT
• decomposes the modules, defines the procedure in it and verifies the
correctness of it.
UNIT I 54

RECURSION
A recursive function is one that calls itself directly
or indirectly to solve a smaller version of its task
until a final call which does not require a self-
call.
UNIT I 55

RECURSION
• Top–down approach to problem solving
• Divides the problem into pieces or selects one key step, postponing the rest.
• Decomposition into smaller problems of same type
• Recursive calls must diminish problem size
• Necessity of base case(An instance of a problem the solution of which requires no further recursive calls)
• Base case must be reached
• It acts as a terminating condition. Without an explicitly defined base case, a recursive function would call itself
indefinitely.
• It is the building block to the complete solution.
UNIT I 56

SYNTAX FOR RECURSION
if(this is a base case) then
solve it directly
else
redefine the problem using recursion.
UNIT I 57

Questions
• What is mean by flowchart?
• What is mean by pseudocode?
UNIT I 58

Introduction to C
Programming
UNIT I 59

What is C?
•Programming language
•Written by Dennis Ritchie
•Developed at AT & T’s Bell Lab
•Country : USA
•Year :

Features of C
•General purpose language
•Portability
•Code re-usability & ability to customize and extend
•Limited number of keyword
•Structured language

What is C used for?
Systems programming:
• OSes, like Linux
• microcontrollers: automobiles and airplanes
• embedded processors: phones, portable electronics, etc.
• DSP processors: digital audio and TV systems

Version of C:
Year Version
1972 Invention of C
1978 K & R C
1983 ANSI established a committee to standardize the C language
1989 ANSI C / C89
1990 ANSI or ISO C90
1999 ANSI or ISO C99
2011 *ANSI or ISO C11
UNIT I 63
*ANSI (American National Standard Institute)
ISO (International Organization for standardization)

Writing C programs
• Save c program with .c extension (Ex: add.c)
• C program must be created in two stages:
• Run your program
Source Code : the program is written in the form of text files
Note: A computer cannot execute source code directly (aaa.c)
Executable code (Object file) : the completed source code is processed with a compiler.
(aaa.obj)
Stage 1
Stage 2
Compiler
a=b+c;
101001110…

Errors
• Errors are mistakes that programmers make in their code.
• Two kinds of errors:
• Compile-time errors
• caught by compiler
• Syntax errors
• Ex: missing semicolon
• run-time errors
• Errors that occur in a compiled and running program
• Ex: division by zero error
Syntax refers to the protocols to be
followed while writing a program.

Questions
• Author of C programming language?
• What is a compiler?
• What are the kinds of error that can occur in a program?
• If you had some C source code that you wished to call “addition”,
under what name would you save it?
• What would be the name of the executable file for the program in the
last question?

KEY WORDS
• ASCII : It is a standard code for representing characters as numbers that is used on most microcomputers,
computer terminals, and printers. In addition to printable characters, the ASCII code includes control characters to
indicate carriage return, backspace, etc. Ex: A -> 65 -> 0100 0001
• Assembler :The assembler creates the object code.
• Associativity :The associativity of operators determines the order in which operators of equal precedence are
evaluated when they occur in the same expression. Most operators have a left-to-right associativity, but some have
right-to-left associativity. Ex: 10 + 20 * 30
100 / 10 * 10
UNIT I 67

For example: Solve
100 + 200 / 10 - 3 * 10
• = 100 + 200 / 10 – 3 *10
• = 100 + 20 – 3 * 10
• = 100 + 20 – 30
• = 120 – 30
•
UNIT I 68

KEY WORDS
• Compiler: A system software that translates the source code to assembly code.
• Constant :A constant is an entity that doesn’t change. Ex: pi = 3.14
• Data type: The type, or data type, of a variable determines a set of values that the
variable might take and a set of operations that can be applied to those values.
• Ex: integer, float, char
• Debugger: A debugger is a program that enables you to run another program step-
by-step and examine the value of that program’s variables.
• Identifier: An identifier is a symbolic name used in a program and defined by the
programmer. Ex: mark = 90
UNIT I 69

KEY WORDS
• IDE :An Integrated Development Environment or IDE is an editor which offers a
complete environment for writing, developing, modifying, deploying, testing, and
debugging the programs. Ex: Dec
• Identifier: An identifier or name is a sequence of characters invented by the programmer
to identify or name a specific object.
• Keyword: Keywords are explicitly reserved words that have a strict meaning as
individual tokens to the compiler. They cannot be redefined or used in other contexts. Ex:
if, else, for, while, …
UNIT I 70

KEY WORDS
• Linker: If a source file references library functions or functions defined in other
source files, the linker combines these functions to create an executable file.
• Precedence :The precedence of operators determines the order in which different
operators are evaluated when they occur in the same expression. Operators of
higher precedence are applied before operators of lower precedence.
• Pre processor :The C pre processor is used to modify the source program before
compilation according to the pre processor directives specified.
Ex: #include<stdio.h>
UNIT I 71

KEY WORDS
• Lvalue: An lvalue is an expression to which a value can be assigned. Ex: x = y + z
• Rvalue: An rvalue can be defined as an expression that can be assigned to an lvalue.
• Token: A token is one or more symbols understood by the compiler that help it
interpret your code.
• Word: A word is the natural unit of memory for a given computer design. The word
size is the computer’s preferred size for moving units of information around;
technically it’s the width of the processor’s registers. (32 or 64)
UNIT I 72

KEY WORDS
• Whitespace Space, newline, tab character and comment are collectively known as whitespace.
• Variable: A variable is a named memory location. Every variable has a type, which defines the possible
values that the variable can take, and an identifier, which is the name by which the variable is referred.
Ex: int mark = 90;
• Bug:Any type of error in a program is known as bug. There are three types of errors that may occur:
⮚ Compile errors,
⮚ Linking errors,
⮚ Runtime errors
UNIT I 73

Steps in learning in C
• Steps in learning English language:
• Steps in learning C:
Alphabets Words Sentences Paragraphs
Alphabets
Digits
Special Symbols
Constants
Variables
Keywords
Instructions Program

C Character Set
• A character denotes any alphabet, digit, or special symbol used to
represent information.

Constants
• A constant is an entity that does not change.
• Examples:
• 100
• 3.14
• ‘A’
• “welcome”

Variables
• A variable is an entity that may change during execution of the
program.
• Example:
• X=10;
•
Address Data Name of the
variable
100
101
102
103
104
….
variable
100
101
102 10 X
103
104
….
variable
100
101
102 20 X
103
104
….

Variable names
Naming rules:
• Variable names can contain letters, digits and _
• Variable names should start with letters or underscore.
• Keywords (e.g.,for, while etc.) cannot be used as variable names
• Variable names are case sensitive. int x; int X declares two different variables.
• Total$marks – incorrect
• Total_marks - correct

Declaration of variables
• Must declare variables before use
• Syntax:
Example:
int mark;
char grade;
flat average;
int a, b, c;
datatype_name variable_name1, variable_name2,…,variable_name n;

Initialization
• Variables initialized via assignment operator
• Syntax:
Example:
int mark = 80;
char grade = ‘A’;
flat average = 75.8;
int a, b, c=10, d=5;
datatype_name variable_name = value;

Keywords
• Keywords are the words whose meaning has already been explained to
the C compiler.
• 32 keywords available in C.
• Reserved words

Identify the parts of a program:
UNIT I 82

Basic Structure of C program
1. /*
2. Documentation section
3. C programming structure
4. Author: XYZ
5. */
6. #include <stdio.h> // Link section
7. int subtract = 0; // Global declaration, definition section
8. void main () // Main function
9. {
10. int a=20, b=10; // Declaration part
11. subtract= a – b; // Executable part
12. printf ("Subtraction of the two numbers : %d n", subtract);
13. }

ILLUSTRATED VIRSION OF A PROGRAM
UNIT I 85

• The header files, usually incorporate data types, function declarations and macros,
resolves this issue. The file with .h extension is called header file, because it’s usually
included at the head of a program.
• Every C compiler that conforms to the international standard (ISO/IEC 9899) for the
language will have a set of standard header files supplied with it.
• The header files primarily contain declarations relating to standard library functions
and macros that are available with C.
Header File
UNIT I 88

• During compilation, the compilers perform type checking to ensure that the calls to
the library and other user-defined functions are correct. This form of checking helps
to ensure the semantic correctness of the program.
STANDARD HEADER FILES
UNIT I 89

• main() is a user defined function. main() is the first function in the program which gets called when the
program executes. The start up code c calls main() function. We can’t change the name of the main()
function.
• main() is must.
• According to ANSI/ISO/IEC 9899:1990 International Standard for C, the function called at program start
up is named main. The implementation declares no prototype for this function. It can be defined with no
parameters:
int main(void) { /* ... */ }
• or with two parameters (referred to here as argc and argv) :
• int main(int argc, char *argv[ ]) { /* ... */ }
PHILOSOPHY : MAIN
UNIT I 90

STRUCTURE : C PROGRAM
UNIT I 91

• Declaration means describing the type of a data object to the compiler but not allocating any
space for it.
⮚ A declaration announces the properties of a data object or a function. If a variable or function is declared
and then later make reference to it with data objects that do not match the types in the declaration, the
compiler will complain.
⮚ data_type variable_name_1,
• Definition means declaration of a data object and also allocating space to hold the data object.
⮚ A definition, on the other hand, actually sets aside storage space (in the case of a data object) or
indicates the sequence of statements to be carried out (in the case of a function).
DECLARATION & DEFINITION
UNIT I 92

• All variables have three important attributes:
⮚A data type that is established when the variable is defined, e.g., integer, real,
character. Once defined , the type of a C variable cannot be changed.
⮚ A name of the variable.
⮚ A value that can be changed by assigning a new value to the variable. The
kind of values a variable can assume depends on its type. For example, an
integer variable can only take integer values, e.g., 2, 100, –12.
VARIABLES:ATTRIBUTES
UNIT I 93

CLASSIFICATION :DATA TYPE
UNIT I 95

Primary Data Types in C
• int: It is responsible for storing integers. In general, int data type occupies 4 bytes of memory
when working with a 32-bit compiler.
Ex: 1324, +500
• float: It is responsible for storing fractions or digits up to 7 decimal places. It occupies 4 bytes of
memory. Ex: 35.78
• char: It can be used to store a set of all characters which may include alphabets, numbers and
special characters. It occupies 1 byte of memory. Ex: ‘A’, ‘a’
• double: It is responsible for storing fractions or digits up to 15-16 decimal places. It occupies 8
bytes of memory. Ex: 4.1e8
• void (Null) data type: It indicates zero or no return value. It is generally used to assign the null
value while declaring a function.

• 16 bit computer:
• 32 bit computer:
BASIC DATA TYPES:SIZE & RANGE
UNIT I 97

• In addition, C has four type specifiers or modifiers and three type qualifiers.
⮚Each of these type modifiers can be applied to the base type int.
⮚The modifiers signed and unsigned can also be applied to the base type char.
⮚In addition, long can be applied to double.
⮚When the base type is omitted from a declaration, int is assumed.
⮚The type void does not have these modifiers.
SPECIFIER OR MODIFIERS
UNIT I 98

Questions
• What are the basic data types in C?
• How many bytes are occupied by basic data types in C?
UNIT I 99

• The specifiers and qualifiers for the data types can be broadly classified into three types:
⮚ Size specifiers— short and long
⮚ Sign specifiers— signed and unsigned
⮚ Type qualifiers— const, volatile and restrict
SPECIFIERS : DATA TYPES
UNIT I 100

• A statement is a syntactic constructions that performs an action when a program is
executed. All C program statements are terminated with a semi-colon (;).
PROGRAM STATEMENTS
UNIT I 102

• Declaration :It is a program statement that serves to communicate to the language
translator information about the name and type of the data objects needed during
program execution. Ex: int x;
• Expression statement: It is the simplest kind of statement which is no more than an
expression followed by a semicolon. An expression is a sequence of operators and
operands that specifies computation of a value . Example : x = 10 + 20;
• Compound statement is a sequence of statements that may be treated as a single
statement in the construction of larger statements.
• Labelled statements can be used to mark any statement so that control may be
transferred to the statement by switch statement.
Cont.
UNIT I 103

• Control statement is a statement whose execution results in a choice being made as
to which of two or more paths should be followed. In other words, the control
statements determine the ‘flow of control’ in a program.
⮚Selection statements allow a program to select a particular execution path from a set of one
or more alternatives. Various forms of the if..else statement belong to this category.
⮚Iteration statements are used to execute a group of one or more statements repeatedly. “while,
for, and do..while” statements falls under this group.
⮚Jump statements cause an unconditional jump to some other place in the program. Goto
statement falls in this group
Cont.
UNIT I 104

• Storing unsigned integers is a straightforward process . The number is changed to the
corresponding binary form & the binary representation is stored.
HOW THE INTEGERS ARE STORED IN
MEMORY
UNIT I 105

• For signed integer types, the bits of the object representation shall be divided into three
groups: value bits, padding bits, and the sign bit. There need not be any padding bits;
there shall be exactly one sign bit (if there are M value bits in the signed type and N in the
unsigned type, then M ≤ N). If the sign bit is zero, it shall not affect the resulting value. If
the sign bit is one, the value shall be modified in one of the following ways:
⮚ the corresponding value with sign bit 0 is negated(sign and magnitude);
⮚ the sign bit has the value −(2N) (2’s complement);
⮚ the sign bit has the value −(2N − 1) (1’s complement).
HOW THE INTEGERS ARE STORED IN
MEMORY
UNIT I 106

INTEGER STORING:PROCESS
UNIT I 107

• Compiler vendors (like Microsoft, Borland ,etc.) provide their own keywords apart from
the ones mentioned below. These include extended keywords like near, far, asm, etc.
KEY WORDS
UNIT I 108

• A constant is an explicit data value written by the programmer. Thus, it is a value
known to the compiler at compiling time.
• In ANSI C, a decimal integer constant is treated as an unsigned long if its
magnitude exceeds that of the signed long. An octal or hexadecimal integer that
exceeds the limit of int is taken to be unsigned; if it exceeds this limit, it is taken to
be long; and if it exceeds this limit, it is treated as an unsigned long.
• An integer constant is regarded as unsigned if its value is followed by the letter
‘u’ or ‘U’, e.g.,0x9999u; it is regarded as unsigned long if its value is followed by
CONSTANT
UNIT I 109

SPECIFICATIONS OF DIFFERENT
CONSTANTS
UNIT I 110

OPERATORS AND EXPRESSIONS
UNIT I 111

CLASSIFICATION:OPERATORS IN C
UNIT I 112

DIFFERENT OPERATORS
UNIT I 113

• There are three types of arithmetic operators in C:binary,unary, and ternary.
• Binary operators: C provides five basic arithmetic binary operators.
⮚Arithmetic binary operators:
ARITHMETIC OPERATOR
UNIT I 114

• Unary operators: The unary ‘–’ operator negates the value of its operand (clearly, a
signed number). A numeric constant is assumed positive unless it is preceded by the
negative operator. That is, there is no unary ‘+’. It is implicit. Remember that -x does not
change the value of x at the location where it permanently resides in memory.
• Unary increment and decrement operators ‘++’ and ‘--’ operators increment or
decrement the value in a variable by 1.
• Basic rules for using ++ and – – operators:
⮚The operand must be a variable but not a constant or an expression.
⮚ The operator ++ and -- may precede or succeed the operand.
UNARY OPERATION
UNIT I 115

Postfix:
• (a) x = a++;
⮚ First action: store value of a in memory location for variable x.
⮚ Second action: increment value of a by 1 and store result in memory location for variable a.
• (b) y = b––;
⮚ First action: put value of b in memory location for variable y.
⮚ Second action: decrement value of b by 1 and put result in memory location for variable b.
POSTFIX
UNIT I 116

Prefix :
• (a) x = ++a;
⮚ First action: increment value of a by 1 and store result in memory location for variable a.
⮚ Second action: store value of a in memory location for variable x.
• (b) y = ––b;
⮚ First action: decrement value of b by 1 and put result in memory location for variable b.
⮚ Second action: put value of b in memory location for variable y
PREFIX
UNIT I 117

• C provides six relational operators for comparing numeric quantities. Relational operators evaluate to 1, representing the true outcome, or 0, representing the
false outcome.
RELATIONAL OPERATORS
UNIT I 118

• C provides three logical operators for forming logical expressions. Like the
relational operators, logical operators evaluate to 1 or 0.
⮚Logical negation is a unary operator that negates the logical value of its single operand. If its
operand is non-zero, it produces 0, and if it is 0, it produces 1.
⮚Logical AND produces 0 if one or both its operands evaluate to 0. Otherwise, it produces 1.
⮚Logical OR produces 0 if both its operands evaluate to 0. Otherwise , it produces 1.
LOGICAL OPERATORS
UNIT I 119

• C provides six bitwise operators for manipulating the individual bits in an integer
quantity . Bitwise operators expect their operands to be integer quantities and treat
them as bit sequences.
⮚Bitwise negation is a unary operator that complements the bits in its operands.
⮚Bitwise AND compares the corresponding bits of its operands and produces a 1 when both bits are
1, and 0 otherwise.
⮚ Bitwise OR compares the corresponding bits of its operands and produces a 0 when both bits are 0,
and 1 otherwise.
⮚Bitwise exclusive or compares the corresponding bits of its operands and produces a 0 when both
bits are 1 or both bits are 0, and 1 otherwise.
BIT WISE OPERATORS
UNIT I 120

Questions
• Types of operators in C
UNIT I 121

• The conditional operator has three expressions.
⮚ It has the general form expression1 ? expression2 : expression3
⮚First, expression1 is evaluated; it is treated as a logical condition.
⮚If the result is non-zero, then expression2 is evaluated and its value is the final result. Otherwise,
expression3 is evaluated and its value is the final result.
• For example,int m = 1, n = 2, min;
min = (m < n ? m : n); /* min is assigned a value 1 */
• In the above example, because m is less than n, m<n expression evaluates to be true,
therefore, min is assigned the value m, i.e., 1.
CONDITIONAL OPERATOR
UNIT I 122

• This operator allows the evaluation of multiple expressions, separated by the comma,
from left to right in order and the evaluated value of the rightmost expression is
accepted as the final result. The general form of an expression using a comma
operator is
• Expression M = (expression1, expression2, …,expression N);
• where the expressions are evaluated strictly from left to right and their values
discarded, except for the last one, whose type and value determine the result of the
overall expression.
COMMA OPERATOR
UNIT I 123

• C provides a useful operator, sizeof, for calculating the size of any data item or type. It takes a single operand that may be a type name (e.g., int) or an expression (e.g.,100) and returns the size of the specified
entity in bytes .The outcome is totally machine-dependent.
⮚ For example:
SIZEOF OPERATOR
UNIT I 124

• Evaluation of an expression in C is very
important to understand. Unfortunately there is
no ‘BODMAS’ rule in C language as found in
algebra.
• The precedence of operators determines the
order in which different operators are evaluated
when they occur in the same expression.
Operators of higher precedence are applied
before operators of lower precedence.
EXPRESSION EVOLUATION: PRECEDENCE &
ASSOCIATIVITY
UNIT I 125

EXAMPLE : OPERATOR PRECEDENCE
UNIT I 126

• An lvalue is an expression to which a value can be assigned .
• An rvalue can be defined as an expression that can be assigned to an lvalue.
• The lvalue expression is located on the left side of an assignment statement, whereas an
rvalue is located on the right side of an assignment statement.
• The address associated with a program variable in C is called its lvalue; the contents of
that location are its rvalue, the quantity that is supposed to be the value of the variable.
• The rvalue of a variable may change as program execution proceeds; but never its lvalue.
The distinction between lvalues and rvalues becomes sharper if one considers the
assignment operation with variables a and b.
LVALUES AND RVALUES
UNIT I 127

• For example :
⮚a = b;
⮚b, on the right-hand side of the assignment
operator, is the quantity to be found at the
address associated with b, i.e., an rvalue. a is
assigned the value stored in the address
associated with b. a, on the left-hand side, is
the address at which the contents are altered as
a result of the assignment. a is an lvalue. The
assignment operation deposits b’s rvalue at a’s
LVALUES AND RVALUES
UNIT I 128

• Though the C compiler performs automatic type conversions, the programmer should be aware of
what is going on so as to understand how C evaluates expressions.
⮚ When a C expression is evaluated, the resulting value has a particular data type. If all the variables in the expression
are of the same type, the resulting type is of the same type as well. For example, if x and y are both of int type , the
expression x +y is of int type as well.
⮚ The smallest to the largest data types conversion with respect to size is along the arrow as shown below:
TYPE CONVERSION
UNIT I 129

⮚float operands are converted to double.
⮚ char or short (signed or unsigned) are converted to int
(signed or unsigned).
⮚ If any one operand is double, the other operand is also
converted to double, and that is the type of the result; or
⮚If any one operand is long, the other operand is treated as
long, and that is the type of the result;
⮚ If any one operand is of type unsigned, the other operand is
converted to unsigned, or the only remaining possibility is
that Both operands must be int, and that is also the type of
the result.
RULE:TYPE CONVERSION
UNIT I 130

• A complex number is a number with a real part and an imaginary part. It is of the form a + bi where i is the square
root of minus one, and a and b are real numbers. a is the real part, and bi is the imaginary part of the complex
number. A complex number can also be regarded as an ordered pair of real numbers (a, b).
• According to C99, three complex types are supported:
⮚ float complex
⮚ double complex
⮚ long double complex
• C99 implementations support three imaginary types also :
⮚ float imaginary
⮚ double imaginary
⮚ long double imaginary
COMPLEX NUMBERS
UNIT I 131

• To use the complex types, the complex.h header file must be included. The
complex.h header file defines some macros and several functions that accept
complex numbers and return complex numbers.
• To use the complex types, the complex.h header file must be included. The
complex.h header file defines some macros and several functions that accept
complex numbers and return complex numbers. In particular, the macro I represents
the square root of –1. It enables to do the following:
⮚double complex c1 = 3.2 + 2.0 * I;
⮚float imaginary c2= -5.0 * I;
COMPLEX NUMBERS
UNIT I 132

DATA INPUT AND
OUTPUT
UNIT I 133

Input and Output
• C has no built-in statements for input or output.
• A library of functions is supplied to perform these operations. The I/O
library functions are listed the “header” file <stdio.h>.
• You do not need to memorize them, just be familiar with them.
UNIT I 134

Streams
• All input and output is performed with streams.
• A "stream" is a sequence of characters organized into lines.
• Each line consists of zero or more characters and ends with the "newline"
character.
• ANSI C standards specify that the system must support lines that are at
least 254 characters in length (including the newline character).
UNIT I 135

Types of Streams in C
• Standard input stream is called "stdin" and is normally connected to the
keyboard
• Standard output stream is called "stdout" and is normally connected to
the display screen.
• Standard error stream is called "stderr" and is also normally connected to
the screen.
UNIT I 136

Input/Output in C
getchar ( ) ;
• This function provides for getting exactly one character from the
keyboard.
• Example:
char ch;
ch = getchar ( ) ;
UNIT I 137

Input/Output in C
putchar (char) ;
• This function provides for printing exactly one character to the screen.
• Example:
char ch;
ch = getchar ( ) ; /* input a character from kbd*/
putchar (ch) ; /* display it on the screen */
UNIT I 138

Formatted Input with scanf()
scanf ( ) ;
• This function provides for formatted input from the keyboard. The syntax is:
scanf ( “format” , &var1, &var2, …) ;
• The “format” is a listing of the data types of the variables to be input and the & in front
of each variable name tells the system WHERE to store the value that is input. It
provides the address for the variable.
• Example:
float a; int b;
scanf (“%f%d”, &a, &b); UNIT I 139

Formatted Output with printf
printf ( ) ;
• This function provides for formatted output to the screen. The syntax is:
printf ( “format”, var1, var2, … ) ;
• The “format” includes a listing of the data types of the variables to be output and, optionally, some
text and control character(s).
• Example:
float a ; int b ;
scanf ( “%f%d”, &a, &b ) ;
printf ( “You entered %f and %d n”, a, b ) ;
UNIT I 140

Formatted Output with printf
• Format Conversion Specifiers:
d -- displays a decimal (base 10) integer
l -- used with other specifiers to indicate a "long"
e -- displays a floating point value in exponential
notation
f -- displays a floating point value
g -- displays a number in either "e" or "f" format
c -- displays a single character
s -- displays a string of characters
UNIT I 141

DECISION MAKING AND LOOPING
STATEMENTS.
UNIT I 142

CONTROL STATEMENTS INCLUDE
Selection
Statement
s
• if
• if-else
• switch
Iteration
Statement
s
• for
• while
• do-while
Jump
Statement
s
• goto
• break
• continue
• return
UNIT I 143

PROGRAM CONTROL
STATEMENTS/CONSTRUCTS IN ‘C’
Program Control
Statements/Constructs
Selection/Branching
Conditional Type
if if-else if-else-if switch
Unconditional Type
break continue goto
Iteration/Looping
for while
do-
while
UNIT I 144

CONDITIONAL EXECUTION AND
SELECTION
•Selection Statements
•The Conditional Operator
•The switch Statement
UNIT I 145

SELECTION STATEMENTS
One-way decisions using if statement
Two-way decisions using if-else statement
Multi-way decisions
Dangling else Problem
UNIT I 146

ONE-WAY DECISIONS USING IF STATEMENT
Flowchart for if construct
if(TestExpr)
stmtT TestExpr
stmtT
UNIT I 147

WRITE A PROGRAM THAT PRINTS THE LARGEST AMONG
THREE NUMBERS.
Algorithm C Program
1. START #include <stdio.h>
int main()
{
int a, b, c, max;
printf(“nEnter 3 numbers”);
scanf(“%d %d %d”, &a, &b, &c);
max=a;
if(b>max)
max=b;
if(c>max)
max=c;
printf(“Largest No is %d”, max);
return 0;
}
2. PRINT “ENTER THREE
NUMBERS”
3. INPUT A, B, C
4. MAX=A
5. IF B>MAX THEN MAX=B
6. IF C>MAX THEN MAX=C
7. PRINT “LARGEST
NUMBER IS”, MAX
8. STOP
UNIT I 148

TWO-WAY DECISIONS USING IF-ELSE STATEMENT
Flowchart of if-else construct
The form of a two-way
decision is as follows:
if(TestExpr)
stmtT;
else
stmtF;
TestExpr
stmtT stmtF
UNIT I 149

WRITE A PROGRAM THAT PRINTS THE LARGEST AMONG
THREE NUMBERS.
Algorithm C Program
1. START #include <stdio.h>
int main()
{
int a, b, c, max;
printf(“nEnter 3 numbers”);
scanf(“%d %d %d”, &a, &b, &c);
max=a;
if(b>max)
max=b;
if(c>max)
max=c;
printf(“Largest No is %d”, max);
return 0;
}
2. PRINT “ENTER THREE
NUMBERS”
3. INPUT A, B, C
4. MAX=A
5. IF B>MAX THEN MAX=B
6. IF C>MAX THEN MAX=C
7. PRINT “LARGEST
NUMBER IS”, MAX
8. STOP
UNIT I 150

MULTI-WAY DECISIONS
if-else-if ladder
if(TestExpr1)
stmtT1;
else if(TestExpr2)
stmtT2;
else if(TestExpr3)
stmtT3;
.. .
else if(TestExprN)
stmtTN;
else
stmtF; General format of switch
statements
switch(expr)
{
case constant1: stmtList1;
break;
break;
break;
………………………….
………………………….
default: stmtListn;
}
UNIT I 151

FLOWCHART OF AN IF-ELSE-IF
CONSTRUCT
TestExpr
TestExpr
2
TestExpr
N
TestExpr3
stmtT2
stmtTN
stmtT3
stmtTF
stmtT1
UNIT I 152

THE FOLLOWING PROGRAM CHECKS WHETHER A NUMBER GIVEN BY THE
USER IS ZERO, POSITIVE, OR NEGATIVE
#include <stdio.h>
int main()
{
int x;
printf(“n ENTER THE NUMBER:”);
scanf(“%d”, &x);
if(x > 0)
printf(“x is positive n”);
else if(x == 0)
printf(“x is zero n”);
else
printf(“x is negative n”);
return 0;
}
UNIT I 153

NESTED IF
• When any if statement is
written under another if
statement, this cluster is
called a nested if.
• The syntax for the
nested is given here:
Construct 1 Construct 2
if(TestExprA)
if(TestExprB)
stmtBT;
else
stmtBF;
else
stmtAF;
if(TestExprA)
if(TestExprB)
stmtBT;
else
stmtBF;
else
if(TestExprC)
stmtCT;
else
stmtCF;
UNIT I 154

A PROGRAM TO FIND THE LARGEST AMONG THREE
NUMBERS USING THE NESTED LOOP
#include <stdio.h>
int main()
{
int a, b, c;
printf(“nEnter the three numbers”);
scanf(“%d %d %d”, &a, &b, &c);
if(a > b)
if(a > c)
printf(“%d”, a);
else
printf(“%d”, c);
else
if(b > c)
printf(“%d”, b);
else
printf(“%d”, c);
return 0;
}
UNIT I 155

SOLUTIONS TO DANGLING ELSE PROBLEM
• Use of null else
• Use of braces to enclose the
true action of the second if
With null
else
With braces
if(TestExprA
)
if(TestExprB
)
stmtBT;
else
;
else
stmtAF;
if(TestExprA
)
{
if(TestExprB
)
stmtBT;
}
else
stmtAF;
UNIT I 156

THE CONDITIONAL OPERATOR
An Example
• It has the following simple format:
expr1 ? expr2 : expr3
It executes by first evaluating expr1,
which is normally a relational
expression, and then evaluates either
expr2, if the first result was true, or
expr3, if the first result was false.
#include <stdio.h>
int main()
{
int a,b,c;
printf(“n ENTER THE TWO
NUMBERS:”);
scanf(“%d %d”, &a, &b);
c=a>b? a : b>a ? b :-1;
if(c==-1)
printf(“n BOTH NUMBERS ARE
EQUAL”);
else
printf(“n LARGER NUMBER IS %d”,c);
return 0;
}
UNIT I 157

THE SWITCH STATEMENT
The C switch construct
The general format of a switch
statement is
switch(expr)
{
break;
break;
break;
………………………….
………………………….
default: stmtListn;
}
UNIT I 158

SWITCH VS NESTED IF
⮚The switch differs from the else-if in that switch can test only for
equality, whereas the if conditional expression can be of a test
expression involving any type of relational operators and/or logical
operators.
⮚A switch statement is usually more efficient than nested ifs.
⮚The switch statement can always be replaced with a series of else-if
statements.
UNIT I 159

ITERATION AND REPETITIVE EXECUTION
• A loop allows one to execute a
statement or block of statements
repeatedly. There are mainly two
types of iterations or loops –
unbounded iteration or unbounded
loop and bounded iteration or
bounded loop.
• A loop can either be a pre-test
loop or be a post-test loop as
illustrated in the diagram.
UNIT I 160

“WHILE” CONSTRUCT
Expanded Syntax of “while” and its
Flowchart Representation
while statement is a pretest
loop. The basic syntax of the
while statement is shown
below:
UNIT I 161

AN EXAMPLE
#include <stdio.h>
int main()
{
int c;
c=5; // Initialization
while(c>0)
{ // Test Expression
printf(“ n %d”,c);
c=c-1; // Updating
}
return 0;
}
This loop contains all the parts of a
while loop. When executed in a
program, this loop will output
5
4
3
2
UNIT I 162

TESTING FOR FLOATING-POINT
‘EQUALITY’
float x;
x = 0.0;
while(x != 1.1)
{
x = x + 0.1;
printf(“1.1 minus %f equals %.20gn”, x, 1.1 -x);
}
The above loop never terminates on many computers, because 0.1 cannot
be accurately represented using binary numbers.
Never test floating point numbers for exact equality, especially in
loops.
The correct way to make the test is to see if the two numbers are
‘approximately equal’. UNIT I 163

“FOR” CONSTRUCT
• The general form of the for statement is as follows:
for(initialization; TestExpr; updating)
stmT;
for construct
flow chart
UNIT I 164

EXAMPLE
#include <stdio.h>
int main()
{
int n, s=0, r;
printf(“n Enter the Number”);
scanf(“%d”, &n);
for(;n>0;n/=10)
{
r=n%10;
s=s+r;
}
printf(“n Sum of digits %d”, s);
return 0;
}
UNIT I 165

8.3 “DO-WHILE” CONSTRUCT
The C do-while loop
The form of this loop construct is
as follows:
do
{
stmT; /* body of statements would be
placed here*/
}while(TestExpr);
UNIT I 166

POINT TO NOTE
With a do-while statement, the body of the loop is executed first and the
test expression is checked after the loop body is executed. Thus, the do-
while statement always executes the loop body at least once.
UNIT I 167

AN EXAMPLE
#include <stdio.h>
int main()
{
int x = 1;
int count = 0;
do {
scanf(“%d”, &x);
if(x >= 0) count += 1;
} while(x >= 0);
return 0;
} UNIT I 168

GOTO STATEMENT
The control is unconditionally
transferred to the statement
associated with the label specified
in the goto statement. The form of
a goto statement is
goto label_name;
The following program is used to find the factorial of a
number.
#include <stdio.h>
int main()
{
int n, c;
long int f=1;
printf(“n Enter the number:”);
scanf(“%d”,&n);
if(n<0)
goto end;
for(c=1; c<=n; c++)
f*=c;
printf(“n FACTORIAL IS %ld”, f);
end:
return 0;
}
UNIT I 169

SPECIAL CONTROL STATEMENTS
⮚“return” statements
⮚“break” statements
⮚“continue” statements
UNIT I 170

“BREAK” AND “CONTINUE”
STATEMENTS
break continue
1. It helps to make an early
exit from the block where it
appears.
1. It helps in avoiding the
remaining statements in a
current iteration of the loop
and continuing with the next
Iteration
2. It can be used in all control
statements including switch
construct.
2. It can be used only in loop
constructs.
UNIT I 171

NESTED LOOPS
⮚A nested loop refers to a loop
that is contained within another
loop.
⮚If the following output has to be
obtained on the screen
1
2 2
3 3 3
4 4 4 4
then the corresponding program
will be
#include <stdio.h>
int main()
{
int row, col;
for(row=1;row<=4;++row)
{
for(col=1;col<=row;++col)
printf(“%d t”, row);
printf(“n”);
}
return 0;
}
UNIT I 172

COMMON PROGRAMMING ERRORS
⮚Writing expressions like a<b<c or a==b==c etc.
⮚Use of = instead of ==
⮚Forgetting to use braces for compound statement
⮚Dangling else
⮚Use of semicolon in loop
⮚Floating point equality UNIT I 173

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