Introduction to C programming

Introduction to C-programming
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Session Objectives
• To Learn the elements of C program
• To Learn about variable declarations and data types
• To about Operators and Expressions
• To know about input output operations
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Session Topics
• Introduction to C programming
• History of C
• Operators and Expressions
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• Data Input and Output

Introduction to C
•C is a general purpose computing
programming language.
•C was invented and was first
implemented by Dennis Ritchie
with the Unix Operating System in
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Dennis Ritchie
1972.
•C is often called a middle level
computer language.
•C is a Structured Language.

History of the C language
• ALGOL 60 (1960): the first programming language with block
structures, control constructs, and recursion possibilities.
• BCPL (Basic Combined Programming Language) (1967),
developed by Martin Richards at Cambridge which built a
foundation for many C elements.
• B (1970), developed by Ken Thompson at the Bell Laboratories
for the first UNIX system.
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for the first UNIX system.
• BCPL and B are type less languages whereas C offers a variety
of data types.
• C (1972), written by Dennis Ritchie at Bell Labs for the
implementation of UNIX. With the publication of “The C
Programming Language” in 1978 by Kernighan and Ritchie
evolved into the standard for C.JJ

Usage of C
• C's primary use is for system programming, including
implementing operating systems and embedded system
applications.
• C has also been widely used to implement end-user applications,
although as applications became larger much of that development
shifted to other, higher-level languages.
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shifted to other, higher-level languages.
• One consequence of C's wide acceptance and efficiency is that the
compilers, libraries, and interpreters of other higher-level
languages are often implemented in C.
• You will be able to read and write code for a large number of
platforms – even microcontrollers.

Characteristics of C
• Portability
Portability means it is easy to adapt software written for one type of
computer or operating system to another type.
• Structured programming language
It make use of subroutines by making use of temporary variables.
• Control the memory efficiently
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• Control the memory efficiently
It makes the concept of pointers.
• Various application
Wide usage in all upcoming fields.

4 steps of development of C- program
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Compilers
• Commercial Compilers:
– Microsoft Visual C++
– Borland C++ Builder
• Freeware Compilers:
– Borland C++ 5.5 Compiler,
also called Turbo C
– Dev-C++, free IDE
(Integrated Development
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(Integrated Development
Environment) and
compiler for C and C++
– DJGPP, a DOS based
Compiler for C, C++ and
Pascal
– LCC-Win32, free compiler
for Windows
– GCC, the most famous
compiler

The Simplest C Program
• Let's start with the simplest possible C program and use it both to
understand the basics of C and the C compilation process.
• Type the following program into a standard text editor. Then save
the program to a file named samp.c. If you leave off .c, you will
probably get an error when you compile it, so make sure you
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remember the .c.
#include <stdio.h>
int main()
{
printf(“First program!n");
return 0;
}

Compilation using gcc
1. Use the command mkdir to create a new
directory.
2. Use the text editor vi followed by the name of
the file.Ex: vi sample.c
3. Use the insert mode to type the text.Use the
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3. Use the insert mode to type the text.Use the
Insert key or ‘I’.
4. Save the file using :wq. The file is now saved.
5. Compile using gcc followed by the name of the
file. Ex: gcc sample.c
6. View the output using a.out file. Type ./a.out.

Language
• Means of Communication
• Chinese – Chinese, English – Chinese,
Nepali-Chinese
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Nepali-Chinese

General Structure of a C Program
• Opening comment block
– Should always contain author’s name, name of the file, and
purpose of the program
• Preprocessor directives
– include all header files for needed libraries
– define any useful constants
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• Function prototypes
– Must be declared before the function is called
• Main function
– Program execution begins at the start of main() and ends when it
reaches the end of main()
– Any additional functions called main are ignored.
• Other function definitions

Internal Structure of a C Program
A C source program is a collection of one or more directives,
declarations, and statements contained in one or more source
files.
– Statements: Specify the action to be performed.
– Directives: Instruct the preprocessor to act on the text of the
program.
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program.
– Declarations: Establish names and define linkage
characteristics such as scope, data type, and linkage.
– Definitions: Are declarations that allocate storage for data
objects or define a body for functions. An object definition
allocates storage and may optionally initialize the object.

General Programming Rules
• All C Statements are free-form
– Can begin and end on any line and in any column
• C statements are always terminated with a semicolon “;”.
• Blank lines are ignored
• White space (blanks, tabs and new lines) must separate keywords from
other things
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other things
• Comments –
All text enclosed within “/* ----- */”
Text on the same line following “//”
Examples:
// This is a comment
/* So is
this. */

C Tokens
• Character Set :
– Letters : A..Z, a...z and Digits : 0...9
– Special characters : , . : ; ? ’ “ ! | / ~ -_ $ % # & ^ * + - < > ( ) { } [ ]
– White space : blank space, horizontal tab, vertical tab,carriage return, new
line, form feed.
• C tokens : individual units.
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– Keyword – float, while, for, int,….
– Identifier – main( ) , amount, sum, …
– Constants – -13.5, 500, …
– Strings – “ABC”, “MCA”, …
– Operators – + - * % …
– Special Symbols – [ ] { }…

C Tokens
• There are several rules that you must follow when naming constants and
variables:
Names... Example
CANNOT start with a number 2i
CAN contain a number elsewhere h2o
CANNOT contain any arithmetic operators... r*s+t
CANNOT contain any other punctuation marks... #@x%£!!a
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CANNOT contain any other punctuation marks... #@x%£!!a
CAN contain or begin with an underscore _height_
CANNOT be a C keyword struct
CANNOT contain a space im stupid
CAN be of mixed cases XSquared
• All variables must be declared before using them in a program and Variable
declarations can also be used to initialize the variable. (not good practice)
• We can declare variables in a single statement with the list of variables
separated by commas. Eg. int lower, upper, step;

Keywords used in C
auto double int struct
break else long switch
case enum register typedef
• Fixed meaning, cannot be changed
• Basic building block
• Lowercase
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case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Identifiers, Constants & Variables
Identifiers
• Refers to names of variables, functions,…
• User defined names.
• Uppercase and lowercase.
Constants
• Fixed values.
• Does not changes during execution of program.
• Numeric constant – Integer (decimal, octal,hexadecimal) and Real
• Character constant :
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• Character constant :
• Single character constant
• String constant
• Backslash character constant
Variables
• Data name used to store data value.
• May take different values at different times during execution.
• Chosen by the programmer.
• Letters, digits and ‘_’ are allowed.

Data types
•Primary data types
•User defined data type
•Derived data type (array, function,
structure,..)
•Empty data set
Type Size (bits) Range
char or signed char 8 -128 to 127
unsigned char 8 0 to 256
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unsigned char 8 0 to 256
int or signed int 16 -32768 to 32767
unsigned int 16 0 to 65535
short int or signed short int 8 -128 to 127
unsigned short int 8 0 to 255
long int or signed long int 32 -2147483648 to 1247483647
unsigned long int 32 0 to 4294967295
float 32 3.4 E –38 to 3.4 E + 38
double 64 1.7 E –308 to 1.7 E + 308
long double 80 3.4 E –4832 to 1.1 E +4932

Variable Declarations in C
• All variables must be declared before using them in a program.
• Variable declarations can also be used to initialize the variable.
• We can declare variables in a single statement with the list of variables
separated by commas.
– int lower, upper, step;
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– float fahr, celsius;
– int i=0;
– char backslash = ‘’

Characters Representation
• Characters are represented at the machine level as an integer
• Computers use ASCII (American Standard Code for Information
Interchange) code
• The values used as code range from 0 to 255
• A-Z (upper case) are represented by 65-90
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• A-Z (upper case) are represented by 65-90
• a-z (lower case) are represented by 97-122
• Constants can be defined using the #define construct (symbolic
constant)
• #define LOWER 0
– #define UPPER 300
– #define STEP 20

Test your basic knowledge
• C is ??? Programming language
High level, mid-level, Low-level
• C was invented by ??? In 1972
Madonna, Dennis Taylor, Guy Ritchie, Dennis Ritchie, Dennis the Menace
• Computer understands C.
TRUE or FALSE
• Which language does not have syntax similar to that of C?
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C++, JavaScipt, Perl, Visual Basic, Java
• C is not case sensative.
TRUE or FALSE
• Which is a valid C commnet?
/*/*…*/*/, /*…*/, <!… >, ‘…., //….
• Which is a correct sequence?
coding linking compiling, coding compiling linking, linking compiling coding,
linking coding compiling, compiling coding linking

Test your basic knowledge
• Which is a valid Hello World program?
#include<stdio.c>
int main(){
printf(“Hello
World”);
#include<stdio.h>
int main(){
print(“Hello
World”);
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World”);
return 0; }
World”);
return 0; }
#include<stdio.h>
int main()
printf(“Hello
World”);
return 0; }
#include<stdio.h>
int main(){
printf(“Hello
World”);
return 0; }

Operators in C
Arithmetic operators
–+ Addition
–- Subtraction
–* Multiplication
–/ Division
–% Modulus
Comparison Operators
• > Greater than
• >= Greater than or equal
to
• < Less than
• <= Less than or equal to
• == Identically equal to
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–% Modulus
(remainder) • == Identically equal to
• != Not identically equal
All arithmetic operators
have higher precedence than
the comparison operators.
The top four have higher
precedence (priority of evaluation
order) than the "equal to" and "not
equal to" operators.

Boolean Values in C
– There is no separate Boolean data types in C
– Any variable can be treated as a Boolean value
– Rules of evaluation
• A numerical value of 0 (zero) represents FALSE.
• A numerical value other than zero represents TRUE.
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• A numerical value other than zero represents TRUE.
– When a Boolean expression is evaluated, it returns:
• 0 for FALSE
• 1 for TRUE

Logical Operators
• NOT reverses the truth value of its operand:
Expression Return Value
!1 0
!0 1
• AND returns 1 if both operands return non zero values Expression
Return Value
1 && 1 1
1 && 0 0
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1 && 0 0
0 && 1 0
0 && 0 0
• OR only returns 0 if both operands return zero:
Expression Return Value
1 || 1 1
1 || 0 1
0 || 1 1
0 || 0 0
NOT has higher
precedence than AND,
which has higher
precedence than OR.

Bitwise Logical operator
-- & bit wise AND: 9 & 23 =01001 & 10111=00001
– | bit wise inclusive OR 9|23=01001|10111=11111
– ^ bit wise exclusive OR 9 ^ 23=01001^ 10111=11110
– << left shift - add zeros to the right bit, a << b returns a*2b, 4 <<
2=4*22 = 16
– >> right shift - takes away bit on the right a >> b = a/ 2b 8 >> 2 = 8 /
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– >> right shift - takes away bit on the right a >> b = a/ 2b 8 >> 2 = 8 /
22 =2
– ~ one’s complement-
9 is 0000 0000 0000 1001
~9= 1111 1111 1111 0110 in unsigned int is 65536 and in signed short
int is –10 (convert 1111 1111 1111 0110 using 2’s compliment
notation)
Remember that in signed short int mode, ~x is -1 - x !

Bitwise Logical operator
• The Conditional Operator - It's possible to say: "If this condition is
true, do this.... , otherwise, do this .... " all in one line. This can be
achieves using the CONDITIONAL OPERATOR, which is represented
by is represented by ? :
– It may look a bit odd at first, but it takes 3 expressions as operands, like
this: a ? b : c; a should be a condition you want to test for. b is an
expression that is evaluated if a returns a non zero value (in other words, if
a is true), else expression c is evaluated.
– For example: x<1 ? printf("x<1") : printf("x>=1");
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– For example: x<1 ? printf("x<1") : printf("x>=1");
– Note the 3 separate operands are expressions - the whole line is a
statement. It's a common mistake to put a semi colon in the middle
expression like this:
x<1 ? printf("x<1"); : printf("x>=1"); - this will generate an error when you
compile!
• Increment and decrement
– ++n pre-increment n++ post increment
– --n pre-decrement n-- post decrement

Operators in C
• Assignment operations
– True for the following operators
+ - * / % << >> & ^ |
– Expression of the form: e1 op = e2 is equivalent to e1 = e1
op e2
– Examples
• j += 4; is the same as j = j + 4;
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• j += 4; is the same as j = j + 4;
• x *= y+1; is equivalent to x = x*(y+1)
• What will the value of x be after executing the
following code?
a = 5; b = 6
if (a = b) x = 1;
else x=2;

Rules of Associativity
Operator Associativity
( ) [ ] -> Left to right
! ~ ++ -- - (type) * & sizeof() Right to left
* / % Left to right
+ - Left to right
<< >> Left to right
< <= > >= Left to right
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< <= > >= Left to right
== != Left to right
& Left to right
| Left to right
^ Left to right
&& Left to right
|| Left to right
?: Right to left
= += -= /= %= &= |= ^= Right to left
, Left to right

Mathematical functions
• C compiler support basic math functions like cos, sin,
sqrt,..
– #include<math.h>
• Functions-
– log(x) , acos(x), asin(x), atan(x), cos(x), sin(x), log10(x), pow(x,y),
sqrt(x), csoh(x), sinh(x), tann(x), ceil(x), floor(x), exp(x), fabs(x) ,
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sqrt(x), csoh(x), sinh(x), tann(x), ceil(x), floor(x), exp(x), fabs(x) ,
fmad(x,y)
• Redundant parenthesis do not cause errors or slow down
the execution of an expression
• Use parenthesis to clarify the exact order of evaluation

Console Input/Output Functions
I/O Functions
Console I/O Functions Disk I/O Functions
Unformatted I/O Formatted I/O
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getch( ) putch( )
getche( ) getche( )
getchar( ) putchar( )
gets( ) puts( )
scanf( ) printf( )

Disk Input/Output Functions
I/O Functions
Console I/O Functions Disk I/O Functions
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Character I/O Numeric I/O
String I/O
getc
putc
getw
putw
fscanf
fprintf

Formatted Input Function
scanf( )
int scanf(char *format, args....) -- reads from stdin and puts input in address of
variables specified in argument list.
Returns, number of charecters read.
The address of variable or a pointer to one is required by scanf.
Example: scanf(``%d'',&i);
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Example: scanf(``%d'',&i);
We can just give the name of an array or string to scanf since this
corresponds to the start address of the array/string.
Example:
char string[80];
scanf(``%s'',string);

Formatted Output Function
printf()
• The printf function is defined as follows:
int printf(char *format, arg list ...) --
prints to stdout the list of arguments according specified format string.
Returns number of characters printed.
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Returns number of characters printed.
• The format string has 2 types of object:
• ordinary characters -- these are copied to output.
• conversion specifications -- denoted by % and listed in Table.

Formatted I/O Functions
Between % and format char we can put:
- (minus sign)
– -- left justify.
integer number
– -- field width.
-- m = field width, d = precision of number of digits after decimal point
or number of chars from a string.
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or number of chars from a string.
So:
printf("%-2.3f n",17.23478);
The output on the screen is:
17.235
and:
printf("VAT=17.5%% ");
...outputs:
VAT=17.5%

Program illustrating Formatted I/O Functions
#include <stdio.h>
int main()
{
int day;
int month;
int year;
char name[30];
printf(“Enter your name:n”>
scanf(“%s”, name);
Note: no ampersand for strings
Conversion specifier
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scanf(“%s”, name);
/* skipping spaces */
printf(“Hi %s. Enter birthdate as: dd mm yyyyn”, name);
scanf("%d %d %d", &day, &month, &year);
/* alternative */
printf(“Hi %s. Enter birthdate as: dd-mm-yyyyn”, name);
scanf("%d-%d-%d", &day, &month, &year);
return 0;
}
Conversion specifier
Literal characters

Unformatted Console I/O Functions
getch( ) and getche( )
This function will read a single character the instant it is
typed without waiting for the Enter key to be hit.
These functions return the character that has been more
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These functions return the character that has been more
recently typed.
The ‘e’ in getche() function means it echoes(displays) the
character that has been typed.
The getch() just return the character that has been typed
without echoing it on the screen.

getchar( ) and putchar( )
The getchar( ) accepts a single character the instant it has
been typed.
The getchar( ) echoes the character that has been typed.
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The getchar( ) echoes the character that has been typed.
It requires the Enter key to be typed following the
character that has been typed.
The functions putch() and putchar() print the character on
the screen.

Program illustrating Console Input Functions
main()
{ char ch;
printf(“Hellon”);
getch();
printf(“Type any charactern”);
ch=getche();
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ch=getchar();
}
Output:
Hello
Type any character A
Type any character B

Program illustrating Console Output Functionsmain()
{ char ch=‘D’;
putch(ch);
putchar(ch);
putch(‘S’);
putchar(‘S’);
}
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}
Output:
DDSS

gets( ) and puts( )
The function gets() receives a string from the keyboard.
It is terminated when an Enter key is hit.
The spaces and tabs are acceptable as part of the input
string.
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string.
The gets() function gets a newline ‘n’ terminated string of
charecters and replaces the ‘n’ with ‘0’.
The puts() function outputs a string to the screen.

Program illustrating Console I/O Functions
main()
{
char arr[25] ;
puts(“Enter namen”);
gets(arr);
puts(“Welcomen”);
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puts(arr);
}
Output:
Enter name
Embedded Systems
Welcome
Embedded Systems

Summary
• C is a general purpose computing programming language
which was invented and was first implemented by Dennis
Ritchie
• The main characteristics of C language are portability,
structured programming, memory efficiency etc.,
• Data types supported by C language are integer, float,
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• Data types supported by C language are integer, float,
double, character etc.,
• Both formatted and unformatted input output statements
are supported by C

Introduction to C programming

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