Notes of c programming 1st unit BCA I SEM

Subject: C and Data Structures
C LANGUAGE CONTENTS
CHAPTER - I
 Basic structure of C program
 C tokens
 Data types and sizes
 Declaration of variables
 Assigning values
 Operators
 Type conversions,
 Expressions and evaluation
 Input-Output statements
CHAPTER - II
 If and switch statement,
 While
 Do-While
 For statement
.CHAPTER – III
 One dimensional & two dimensional arrays
 Strings and String handling functions
 Functions, Recursive functions, Storage classes, and Scope rules
CHAPTER - IV
 Pointers, Pointers and Arrays, Pointers and function arguments,
 Pointers to functions.
 Structures
 Unions
CHAPTER – V
 Console & File I/O
PREPARED BY : Mansi Tyagi ..

UNIT-I
Introduction
Now a days computers are playing very vital role in each and
every field of problem solving. The communication medium between a computer and a
human being is a typical 'language' i.e.. Humans are able to communicate with the
computer system in some form of language. There are basically three types of languages
viz.. Machine Understandable Language. Assembly Level Language and High Level
Language. There are number of high level languages developed in the past three decades
like FORTRAN, Pascal and Basic, C Language etc. Clearly, no other language has had
so much of influence in the computing as 'C'-language. Evolution of 'C'- as a
programming language has made application development very easy.
ALGORITHM
An algorithm is a method of representing the step-by-step procedure for solving a
problem. An algorithm is useful for finding the right answer to a problem or to a difficult
problem by breaking the problem into simple cases.
An algorithm must possess the following properties:
i) Finiteness : An algorithm should terminate in a finite number of steps.
ii) Definiteness : Each step of the algorithm must be precisely stated.
iii) Effectiveness : Each step must be effective, in the sense that it should be easily
convertible into program statement and can be performed exactly in a finite amount
of time.
iv) Generality : The algorithm should be complete in itself so that it can be used to
solve all problems of a given type for any input data.
v) Input/Output : Each algorithm must take zero, one or more quantities as input data
and yield one or more output values.
Flow chart

Flow chart is diagrammatic representation of an algorithm. It is built using
different types of boxes of symbols. The operation to be performed is written in the box.
All symbols are interconnected by arrows to indicate the flow of information and
processing.
Following are the standard symbols used in drawing flowcharts. (see in next page)
Oval Terminal Start/stop/begin/end
symbol
Parallelogram Input/Output Making data available
for processing (input) or
recording of the
processed
information(output)
Rectangle Process Any processing to be
performed. An
assignment operation
normally represented by
this symbol
Diamond Decision Decision or switching
type of operations that
determines which of the
alternative paths is to be
followed.
Circle Connecter Used for connecting
different parts of flow
chart.
Arrow Flow Joins two symbols and
also represents
executions flow.
Bracket with broken
line
Annotation Descriptive comments
or explanations
Double sided
rectangle
Predefined
process
Modules or subroutines
given elsewhere

Introduction to C:
C is a programming language developed at AT& T’s Bell Laboratories of USA in
1972.It was designed and written by Dennis Ritchie. C has the features of both BASIC
and PASCAL. As a middle language, C allows the manipulation of bits, bytes and
addresses the basic elements with which computer functions.
Importance of C
1) It is a robust language, whose rich set of built-in functions and operators can
be used to write any complex program.
2) Programs written in C are efficient and fast. This is due to its variety of data
types and powerful operators.
3) C’s code is very portable, in the sense that it is easy to adapt software written
for one type of computer or operating system to another type.
4) C has very small key words (only 32). Its strength lies in its built-in
functions. These built-in functions can be used for developing programs.
5) C language is well suited for structured programming, thus requiring the user
to think of a problem in terms of functions (or) blocks. A proper collection of
these functions would make a complete program. This modular structure
makes program debugging, testing and maintenance easier.
6) Another important feature of C is its ability to extend itself.
Basically a C program is a collection of functions that are supported by
the C library. We can add our own functions to the C library. With the
availability of a large number of functions, the programming task becomes
simple.

Simple ‘C’ Program:
Before discussing any features of C, we shall look at some sample C program
and analyze and understand how they work.
Ex 1: C program to print a message.
main()
{
Printf(“welcome to GITAM”)
}
Explanation:
i) main():
i) The ‘main()’ is a special function used by the C system to tell the computer
where
the program starts.
ii) Every program must have exactly one main function.
iii) Opening brace ‘{‘ and closing brace ‘}’ are the delimiters of any function.
iv) All the statements between these two braces are called as function body.
v) The lines beginning with /* and ending with */ are known as comment lines.
These lines are not executable statements and therefore anything between /* and */ is
ignored by the compiler.
ii) printf() function:
printf is a predefined, standard C function for printing output. ‘Predefined’ means
that it is a function that has already been written and compiled, and linked together with
our program at the time of linking.
The printf function causes everything between the starting and the ending
quotation marks to be printed out. In the above example, the out put will be
welcome to RGMCET

• Every statement in C should end with a semicolon(;) mark.
Format of a simple C program:
main()-------------------- function name
{--------------------------- starting of the program
------- ---------------- program statements
-------
}--------------------------- ending of the program
Program development steps:
The following steps are used in sequence for developing an efficient program:
• Specifying the problem statement
• Designing an algorithm
• Coding
• Debugging
• Testing and validating
• Documentation and maintenance
Program execution steps:
• Creating the program (or) typing the program.
• Compiling the program (short-cut key- Alt+F9)
• Linking the program with functions that are needed from the C library.
• Running the program (short-cut key-- Ctrl +F9)

‘C’ LANGUAGE OBJECTIVES
C is a general purpose structured programming language that is powerful,
efficient and compact. C combines the features of high level language. Programming in
C has recently become more interesting.
C language provides the various operators to evaluate various
expressions. C also provides decision making and branching statements. It also
introduces us the concepts of arrays, structures, pointers and strings. Also provides how
to mange files. Also gives the idea of data structures in which the topics stacks, queues,
linked lists, sorting and searching are involved.

Program development steps:
There are two broad categories of programmer, the successful and not so-
successful. The second category people to their keyboards and begin coding i.e. the
actual writing of instructions. It is the mark of professional and successful programmers
that this is one of the last stages they undertake. There are many more important steps to
consider first.
1. Understand the problem:
Unless the problem is clearly understood. You cannot even begin to solve it.
This seems like a truism until you appreciate that a program specification seldom gives
all the fact required by the programmer. The professional programmer is a pessimist,
because from past experience there is always some importance information which is
omitted. This needs to be identified first.
2. Examine the data:
Programs are written to work on data. Unless one knows exactly how the data
is organized, what it ‘looks’ like, etc., the program which processes it cannot be written.
This fact becomes clearer the more one writes programs, but it is a fact all too frequently
overlooked by the novice.
3. Plan the output:
The output should be planned next. Not only does this help to ensure that
nothing is omitted from the program, but helps to get a clear picture of what the program
is trying to achieve and whether the programmer does understand the problem.
4. Designing the solution (Designing the algorithm) :
There are many ways of beginning solution, so much so that entire books are
devoted this subject alone. Computer scientists frequently say that programming is like
any engineering task in that the program has to be designed and constructed in much the
same way as any engineering project. A motorway is not built by starting at point A and
steadfastly pushing on to point X. rather, months are spent in planning; charts designed;
sub tasks identified as well as those which cannot begin until others have been
completed; broad designs are developed and later more detailed designs constructed. It is
only after a long planning period and most effective order of the subtasks is agreed upon

that the construction crews actually begin work. Programming requires this same pains
taking processes, with the end result standing or falling by the amount of care and
attention invested in the planning stage.
5. Selecting test data:
How can one ensure that once a program is eventually working the results it
produces are ‘correct’? The answer is simple commonsense. Try the program out on
some data to which the answers have been worked out in advance. If they match, the
program should be all right. Selecting effective test data is a serious exercise and the
more significant the program, the more care needs to the taken in the selection.
6. The actual coding (Implementation):
At this stage, one can begin to code the detailed program designs into program
instructions of a given language. If all the previous steps have been completed with due
diligence, this coding should be almost ‘automatic’. The chances are high that a fairly
successful program will result first time around. Although it may still contain bugs, these
should be fewer and relatively easy to identify and correct.
7. Testing:
The program can be tested with the test data, results checked and any errors
amended. When all is correct the program can be released and set to work on live data.

History & Evolution of ‘C’ & Basic structure of C program:
Computer languages are classified into generations. Machine language, assembly
language and high level languages are called the first, second and third generation
languages respectively.
That high level languages were designed precisely to address these problems
provided high level control structures, input/output facilities, hardware independents and
so on.
The development of a self contained set of instructions which enable a
computer to perform a specific task is programming. There are a variety of programming
languages such BASIC, COBAL, FORTRAN, PASCAL. As computers gain more
power for less money very sophisticated high level languages are developed, making
programming a creative non specialist task. And one such language developed was ‘C’.
‘C’ seems a strange name for a programming language, but is one of the most popular
computer languages today. ‘C’ was originally developed in the 1970’s by Dennis Ritchie
at Bell telephone laboratories INC. ‘C’ was an offspring of the BCPL (Basic Combined
Programming Language) called B.
The C language is often described as a middle level language, because it
combines the best features of high level languages with the control and flexibility of
assembly language.
Features and applications of C languages:
1. ‘C’ is general purpose structured programming language.
2. ‘C’ is powerful, efficient, compact and flexible.
3. ‘C’ is highly portable.
4. ‘C’ is a robust language whose rich set of built in function and operators can be
used to write any program.
5. ‘C’ is a well suited for writing systems software as well as application
programming.
6. ‘C’ has the ability to extend itself. We can continuously add our own functions to
the existing ‘C’ library functions.

7. ‘C’ programs can be run on any of the different computer with little or no
alteration.
8. ‘C’ is widely available commercial ‘C’ compilers are available on most personal
computers, mini and main frames.
9. ‘C’ language allows reference to a memory location with the help of pointer
which holds the address of the memory location.
10. ‘C’ language allows dynamic allocation of memory i.e. a program can request the
operating system to allocate/release memory.
11. ‘C’ language allows manipulations of data at the lowest level i.e. bit level
manipulation. This feature is extensively useful in writing system software
programs.
12. ‘C’ is a case sensitive language.
Basic structure of C program:
A ‘C’ program can be viewed as a group of building blocks called functions. A
function is a sub-routine that may include one or more statements designed to perform a
specific task. To write a ‘C’ program we first create functions and then put them
together. A ‘C’ program may contain a one or more sections as given below.
Main function section //Must
{
Declaration part
Executable part.
}
Documentation Section //optional
Link section //optional
Defining section //optional
Global declaration section //optional

Sub program section //optional
Function 1
Function 2
Function n
1) The documentations section consists of comment lines giving the name of the
program ,the author and other details which the programmer would like to use later.
these comments beginning with the two Characters * and ending with the characters*.
2) The link section provides to the compiler to link functions from the system library
3) The definition section defines all symbolic constants.
There are some variables that are used in one or more functions, such variables
are called global variables and are declared in the global declaration section that is
outside of all the functions.
4) Every C program must have one main () function section. This section can contain
two
parts; they are Declaration part and Execution part.
• The declaration part declares all the variables used in the executable part.
• There is at least one statement in the executable part.
• These two parts can appear between the opening and closing braces. The
program execution begins at the opening braces and ends at the closing braces.
The closing brace of the function section is the logical end of the program.
• All statements in the declaration and executable parts end with a semicolon.
• The sub program section contains all the user defined functions that are called in
the main () function. User defined functions are generally placed immediately
after the main function.
.

Simple ‘C’ Program:
/*Simple C Program */
main()
{
/*prints the string */
printf(“welcome to C worldn”);
}
• The first and fourth lines are commented lines. These are used in a program to
enhance its readability and understanding .the line beginning with * and ending
with* are known as comment lines. Comment lines are not executable
statements and anything between *and *is ignored by the compiler. These
comment lines can be inserted wherever we want, it cannot be nested i.e. cannot
have comments inside comments.
• The second line informs the system that the name of the program is main() and
the execution begins at this line. The main () is a special function by the C
system to tell the computer where the program starts. Every program must have
exactly one main function. If we use more than one main function cannot know
where the program begins.
• The opening brace “{“ in the third line marks the beginning of the function
main and the closing brace”}” in the last line indicates the end of the
function . the statements between these two braces
• The function body contains two statements, one of them is printf line is an
executable statement. It is a predefined standard C function. The printf function
to be printed out everything which appears in between quotations marks, here
the output will be ”welcome to C world”.

C Tokens
The smallest individual units are called tokens. C programs are written using
these tokens and the syntax of the language. The C has six types of tokens as shown
below:
1. key word
2. identifiers
3. constants
4. operators
5. strings
Character set:
The characters that can be used to form the words, numbers and expressions
depend upon the computer on which the program is run. The characters in C are grouped
into four categories.
1. letters
2. digits
3. special characters
4. white spaces
With these characters are combined to form data types, constants, variables and
key words

1) Key words and identifiers:
In ‘C’ every word is classified into either a key word or an identifier. All key
word have fixed meaning cannot be changed. Keywords serve as a basic building block
for program statements. All the keywords must be written in lower case.
Keywords are the tokens used in C program which have predefined meaning and
these meanings cannot be changed by the programmer. There are 32 keywords. They are
also called as Reserved words. We cannot use them for any other purpose.
Standard key words:
auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for Signed void
default goto sizeof volatile
do if static while
2) Identifiers:
Identifiers refer to the names of the variable, function and arrays. These are user
defined names and consists of sequence of letters and digits.
Rules for giving name to an identifier:
1. Identifiers can consist of letters and digits, must begin with in the alphabets or
underscore, should not contain white space.
2. Both upper case and lower case are permitted although an upper is not equal to
the corresponding lower case letter.
3. It cannot be a keyword.
4. An identifier can be of any length while most compilers of ‘C’ recognize only the
first eight characters.

3) Constants and variables:
The alphabets, numbers and special symbols are properly combines to form a
constants and variables. Let us see what are constants and variables in C.
Constants:
Constants are fixed values that do not change during the execution of program.
Several types of constants are:
Constants
Numeric Character
Integer Float single character constant String
constant
Octal Hexadecimal Decimal
For example in the equations 5x+2y=45 since 5, 2 and 45 cannot change , these are
called constants, where as the quantity X&Y can vary or change hence these are called
variables .
Numeric constants:
i) Integer constants: It refers to a sequence of digits, it has to fallow the below rules:
1. Integer constants must have at least one digit
2. It must not have a decimal point
3. It could be either positive or negative
4. If no sign precedes an integer constant it is assumed to be positive
5. No commas, blank space are allowed.
6. The allowable range for integer constants is -32768 to +32767 (16-bit machine)

integer constants can be specified in decimal, octal, or hexa decimal notation.
i) A decimal integer constant:
It consists of sequence of one or more decimal digit 0 through 9 preceded by an
optional – (or) + sign.The first digit of the sequence cannot be 0 unless the decimal
integer constant is 0.
Ex: 0 276 3412 31467 -7123
Note: Embedded spaces, commas, and non-digit characters are not permitted between
digits.
Ex: 12 727
23,879 are illegal numbers.
$1772
ii) An Octal Integer constant: It consists of any combination of digits from the set 0
through 7,with a leading 0.
Ex: 012
07134
07777
iii) A hexa Decimal integer constants:
It consists of the digit 0, followed by one of the letter x (or) X, followed by a
sequence of one more hexadecimal digits 0 through 9 or letter a through f (or) A through
F represent the numbers 10 through 15.
Ex: 0X1F
Note: we rarely use octal and hexa decimal numbers in programming.
Real Constant: A real constant are sequence of digits with a decimal point(fractional
part) like 45.382.Such numbers are called real(or floating point) constants.
Rules for constructing Real Constants:
1. A Real constant must have least one digit.
2. It must have a decimal point.
3. It could be either positive or negative.
4. Default sign is positive.

5. No commons, black space are not allowed.
Ex: 1.0 1. 0.712 34.576 -7.123
These numbers are shown in decimal notation, having a whole number fallowed
by a decimal point. It is possible to omit digits before the decimal point or digits after the
decimal point.
Ex: 215. .39 -.92 +5. are valid real numbers.
The real numbers may also be expressed in exponential (or, scientific) notation.
For example, the value 215.65 may be written as 2.1565e2 in exponential notation.(e2
means multiply by 10
The general form:
• The mantissa is either a real number expressed in decimal notation or an
integer.
• The exponent is an integer number with an optional + or – sign.
• The letter e separating the mantissa and the exponent can be written in
either lowercase or uppercase
The scientific notation is often used to express numbers that are either very
small or very large.
Ex: 7500000000 may be written as 7.5e9 or 75e8.
Similarly, -0.000000368 is equivalent to -3.68E-7.
(Coefficient) e (integer) = (coefficient) * 10(integer)
mantissa e exponent

Character constant:
Single character constants:
Rules for constructing character constants:
1. A character constant is a single alphabet, a single digit or a single special symbol
enclosed with in a pair of single inverted commas. Both the inverted commas
should point to the left. For example ‘A’ is not valid character constant where as
‘A’ is valid.
2. The maximum length of a character constant can be one character constant.
3. character constants have integer values known as ASCII values.
4. The valid range of a character constant -128 to127. it appears surprising that the
character constant should have a numeric range. Character and integer constant
are often used interchangeably. For example ‘A’ and 65 are one and the
something, since when we say ‘A’ it is replaced by ASCII value, which is 65.
Example; ‘0’ ‘A’ ‘F’ ‘Y’
String constant: A string constant is a sequence of characters enclosed with in a pair of
double inverted commas. The characters may be letters, numbers, special characters and
blank space ……
Ex: ”hello” “1999” “5+4+6” “good bye”
Backslash character constants:
C supports some special backslash character constants that are used in output
functions. Each one of them represents one character, although they consist of two
characters. These character combinations are known as escape sequences.
Constant Meaning
‘a’
‘b’
‘n’
‘’
‘”
‘v’
Alert(bell)
backspace
new line
back slash
double quotation

vertical tab etc…
Variables: A variable is a data name which can be used to store a data value and a
variable may take different values at different times, during execution.
For example, in the equation 5X+2Y = 45 since 5,2 and 45 cannot change, these
are called constants, where as the quantities X &Y can vary or change hence these are
called variables.
Rules for constructing variable names:
1. A variable name is any combination of alphabets, digits and the
underscore character. ANSI standard recognizes a length of 31 characters.
However, the length should not be normally more than 8 characters, since
only the first 8 characters are treated as significant by many compilers.
2. The first character in the variable name must be an alphabet.
3. No commas or blank spaces allowed.
4. No special symbol other than an underscore can be used
Ex: bas_pay , net_salary , month etc.
5. Uppercase and lowercase are significant. That is, the variable Amount is
not the same as amount or AMOUNT.
6. Variables name should not be a keyword.
Data types:
Each data type has predetermined memory requirement and an associated range
of legal values. Every programming language has its own data types. Storage
representations and machine instructions to handle constants differ from machine to
machine.
ANSI C supports four classes of data types.
1. primary (or fundamental) data types

2. user defined data types
3. derived data types
4. Empty data set.
1. Primary data types:
All C compilers support four fundamental data types, namely integer(int),
character(char),floating point(float), and double-precision point(double).various data
types and their terminology used to describe them are given in below fig.,.
Primary data types
Integer floating point character
Signed unsigned float double long double singed unsigned
int short int long int int short int long int
Integers:
C provides three different types of integers they are int, short int and long int. the
difference between these three integers is the number of bytes. The variables of these
types occupy and subsequently the range of values. A short int occupies 2 bytes, an int
occupies 2 bytes and the long int occupies 4 bytes.
Type Bytes required Range
Short int 2 -32768 to 32767 (-215
to 215
-
1)
int 2 -32768 to 32767 (-215
to 215
-
1)
long int 4 -2147483848 to
2147483847
unsigned short int 2 0 to 65535
unsigned int 2 0 to 65535

unsigned long int 4 0 to 4294967295
Float:
Like integers floats are divided into three types. They are float, double and long
double. The difference between these three floats are the number of bytes, the variable of
these types occupy and subsequently the range of values. A float occupies 4 bytes, a
double occupies 8 bytes and the long double occupies 10 bytes.
Type Description Size Range
Float Single precession 4 3.4E-38 to 3.4E+38
Double Double precession 8 1.7E-308 to
1.7E+308
Long double Extended precession 10 3.4E-4932 to
3.4E+4932
Characters:
A char is a data type which can store an element of machine character set. A
single character can be defined as a character (char) type data. Characters are usually
stored in 8 bits (1 byte) of internal storage. The character set is usually the ASCII. These
are two types, they are signed and unsigned characters. The differences between these
two types are the range of values. Both will occupy one byte.
Type Bytes required Range
Signed char 1 -128 to 127
Unsigned char 1 0 to 255
Declaration of variables:
This instruction is used to declare the type of variable used in the program. Any
variable used in the program must be declared before using it in any statement. The type
declaration statement is usually written at the beginning of the C program.
Syntax:
Data_type var1,var2 … var n;
Ex: int I, count;
Float price, salary;
Char c;

Scope of variables: scope of variables implies to the availability with in a program.
Variables have two types of scopes: local and global.
A variable with a global scope is accessible to all statements in a program but the
one with local scope in restricted to be accessed by only certain selected statements in
the program, in which it is defined.
Global variables are declared outside all functions where as local variables are
defined inside a function.
User-defined data type:
The users can define an identifier that represent an existing data type by a feature
known as “type definition”. The user defined data type identifier can later be used to
declare variables.
General form:
where type refers to an existing data type and identifier refers to the new name given to
the data type.
Ex:
typedef int Sno;
typedef float salary;
Here Sno symbolizes int and salary symbolizes float. These can be used to
declare variables as follows.
Sno c1,c2;
salary e1,e2;
Note: The main advantage of typedef is that we can create meaningful data type names
for increasing the readability of the program.
typedef type identifier;

Another user defined data type is enumerated data type provided by ANSI .
General form: enum identifier {value 1, value 2, ……, value n};
The identifier is a user defined enumerated data type which can be used to
declare variables that can have one of the values enclosed within the braces. After that
we can declare variables to be of this new type.
enum identifier v1, v2, ….vn;
the enumerated variables v1, v2, …..vn can only have one of the value 1, value 2, ……
value n.
Ex 1:
enum month {january, february, ….december};
enum month month_st, month_end;
(or)
enum month {january, february, …., December} month_st, month_end;
Here the declaration and definition of enumerated variables can be combined in
one statement.
Ex 2:
enum day{Monday,Tuesday……Sunday};
enum day week_st,week_end;
week_st=Monday;
week_end=Friday;
if(week_st==Tuesday)
week_end=Saturday;
The compiler automatically assigns integer digits beginning with 0 to all the
enumeration constants. That is, the enumeration constant Monday is assigned with 0,
Tuesday is assigned with 1 and so on. However, the automatic assignments can be
overridden by assigning values explicitly to the enumeration constants.

For example,
enum day{Monday=1,Tuesday, ……., Saturday};
here, the constant Monday is assigned the value 1.The remaining constants are assigned
values that increases successively by 1.
Derived data types
There are some derived data types which are supported by C such as arrays,
functions, structures, and pointers.
Empty data set
It is also known as void data types. It indicates that no other data types has been
used with the given identifier.

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